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ANSYS FLUENT 12.0 UDF Manual

1. 7 03e 02 5 62e 02 4 22e 02 2 81e 02 1 41e 02 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 1 2 Velocity Magnitude Contours for a Constant Inlet x Velocity 1 43e 01 1 31e 01 1 196 01 tibeti fae oe oe eS SS eee 9420 Uh at ig i es ok eh ep eh eh ro 8 20e 02 e eee eae e02 ae ek a a ee a Se 5 75e 02 4 52e 02 3 30e 02 2 076 02 Velocity Vectors Colored By Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 1 3 Velocity Vectors for a Constant Inlet x Velocity Release 12 0 ANSYS Inc January 26 2009 8 3 Examples Now suppose that you want to impose a non uniform x velocity to the duct inlet which has a parabolic shape The velocity is 0 m s at the walls of the inlet and 0 1 m s at the center To solve this type of problem you can write a custom profile UDF and apply it to your ANSYS FLUENT model 8 1 3 Step 2 Create a C Source File Now that you have determined the shape of the velocity profile that defines the UDF you can use any text editor to create a file containing C code that implements the function Save the source code file with a c extension e g myexample c in your working folder The following UDF source code listing contains only a single function Your sour
2. FUNCTION RKEOS_enthalpy Returns specific enthalpy given T and rho double RKEOS_enthalpy double temp double density double P double yi double delta_h press v double afun a0 pow TCRIT temp NRK press RKEOS_pressure temp density v 1 density delta_h press v rgas temp afun 1 NRK b0 1log v b0 v return H_REF RKEOS_H_ideal_gas temp delta_h J Kg Release 12 0 ANSYS Inc January 26 2009 8 61 Examples FUNCTION RKEOS_entropy Returns entropy given T and rho double RKEOS_entropy double temp double density double P double yi double delta_s v v0 dadt cp_integral double afun a0 pow TCRIT temp NRK cp_integral CC1 log temp temp CC2 temp 0 5 CC3 temp 0 333333 CC4 0 25 CC5 temp cp_int_ref v 1 density vO rgas temp P_REF dadt NRK afun temp delta_s rgas log v bb v0 dadt b0 log v b0 v return S_REF cp_integraltdelta_s J Kg K FUNCTION RKEOS_mw Returns molecular weight double RKEOS_mw double yi return MWT Kg Kmol 8 62 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF
3. Define gt User Defined Memory User Defined Memory Number of User Defined Memory Locations qg a iv Figure 6 1 13 The User Defined Memory Dialog Box The macros C_UDMI or F_UDMI can be used in your UDF to access a particular user defined memory location in a cell or face respectively See Sections 3 2 3 and 3 2 4 for details Field values that have been stored in user defined memory will be saved to the data file when you next write one These fields will also appear in the User Defined Memory category in the drop down lists in ANSYS FLUENT s postprocessing dialog boxes They will be named User Memory 0 User Memory 1 etc based on the memory location index The total number of memory locations is limited to 500 For large numbers of user defined memory locations system memory requirements will increase 6 2 Hooking Model Specific UDFs This section contains methods for hooking model specific UDFs to ANSYS FLUENT that have been defined using DEFINE macros found in Section 2 3 Model Specific DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respec tively 6 2 1 Hooking DEFINE_CHEM STEP UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_CHEM_STEP UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks d
4. double RKEOS_enthalpy_p double temp double density double P double yi double v 1 density double dvdt RKEOS_dvdt temp density return v temp dvdt FUNCTION RKEOS_viscosity double RKEOS_viscosity double temp double density double P double yil double mu tr tc pcatm tr temp TCRIT tc TCRIT pcatm PCRIT 101325 mu 6 3e 7 sqrt MWT xpow pcatm 0 6666 pow tc 0 16666 pow tr 1 5 tr 0 8 return mu FUNCTION RKEOS_thermal_conductivity double RKEOS_thermal_conductivity double temp double density double P double yil double cp mu cp RKE0S_Cp_ideal_gas temp mu RKEOS_viscosity temp density yi return cp 1 25 rgas mu 8 64 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Export Real Gas Functions to Solver UDF_EXPORT RGAS_Functions RealGasFunctionList RKEOS_Setup initialize RKEOS_density density RKEOS_enthalpy enthalpy RKEOS_entropy entropy RKEOS_specific_heat specific_heat RKEOS_mw molecular_weight RKEOS_speed_of_sound speed_of_sound RKEOS_viscosity viscosity RKEOS_thermal_conductivity thermal_conductivity RKEOS_
5. User Input Section SsSsSsS S S S X SSSS SS SSS SSS SSS SSS SSS SS SSS SSS SSS SS SSS SSS SSS SS ES Define Species name DO NOT use space for naming species void strcpy gas 0 H20 void strcpy gas 1 CH4 void strcpy gas 2 02 void strcpy gas 3 C02 void strcpy gas 4 N2 End Of User Input Section SS S Message0 n MIXTURE_Setup RealGas mixture initialization n Message0 n MIXTURE_Setup Number of Species 4d n n_specs for i 0 i lt n_specs i Message0 n MIXTURE_Setup Specie d s n i gas i concatenate species name into one string and send back to fluent strcat specielist gas 0 for i 1 i lt n_specs i strcat specielist strcat specielist gas i initialize Mw Cp_Parameters Hform Tcrit Pcrit Release 12 0 ANSYS Inc January 26 2009 8 79 Examples Verit Omega NRK for i 0 i lt n_specs i 4 rgas Li a0 i b0 i coli bb i RGASU mw i 0 42747 rgas i rgas i tcrit li tcrit i pcrit i 0 08664 rgas i tcritli pcrit i rgas li tcritli pceritli a0 i vcrit i vcrit i b0 i b0 i vcrit i bO0 i c0 i cp_int_ref i cp 0 i log ref_T ref_T cp 1 i ref_T 0 5 cp 2 i ref _T 0 333333 cp 3 i 0 25 cp 4 i ref_T double MIXTURE
6. C virtual Mass wall Adhesion Drag Lift Collsions slip Heat Mass Reactions Surface Tension Drag Coefficient water iquid air user defined custom _drag libudf Figure 6 3 3 The Phase Interaction Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 57 Hooking UDFs to ANSYS FLUENT Click the appropriate tab e g Drag in the Phase Interaction dialog box and select user defined from the drop down list for the corresponding exchange property e g Drag Coefficient that you desire This will open the User Defined Functions dialog box User Defined Fu custom_drag libudf heat _udf libudf Figure 6 3 4 The User Defined Functions Dialog Box Select the function name e g custom_drag libudf from the list of UDFs displayed in the User Defined Functions dialog box Figure 6 3 4 and click OK The function name will then be displayed in a text box under the exchange property in the Phase Interaction dialog box Click OK to close the Phase Interaction dialog box See Section 2 4 2 DEFINE EXCHANGE PROPERTY for details about DEFINE EXCHANGE PROPERTY functions 6 58 Release 12 0 ANSYS Inc January 26 2009 6 3 Hooking Multiphase UDFs 6 3 3 Hooking DEFINE_HET_RXN_RATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_HET_RXN_RATE UDF the name of the function you supplied as a DEFI
7. Average velocity normal to wall of particles hitting the wall F_UDMI f t AVG_RADI_VELO vel_ortho num_in_data F_UDMI f t AVG_RADI_VELO num_in_data 1 C_UDMI c0 t0 AVG_RADI_VELO F_UDMI f t AVG_RADI_VELO F_UDMI f t NUM_OF_HITS C_UDMI c0 t0 NUM_OF_HITS num_in_data 1 num_in_data 1 F_AREA A f t area NV_MAG A F_STORAGE_R f t SV_DPMS_ACCRETION Mdot area copied from source P_USER_REAL p 0 1 Evaporate DEFINE_DPM_LAW stop_dpm_law p if_cpld if 0 lt P_USER_REAL p 0 P_MASS p 0 Evaporate J DEF INE_ON_DEMAND reset_UDM assign domain pointer with global domain domain Get_Domain 1 reset_UDM_s Hooking an Erosion Accretion UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_EROSION is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model dialog box in ANSYS FLUENT See Section 6 4 4 Hooking DEFINE_DPM_EROSION UDFs for details on how to hook your DEFINE_DPM_EROSION UDF to ANSYS FLUENT 2 1 72 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 5 DEFINE_DPM_HEAT_MASS Description You can use DEFINE DPM HEAT MASS to specify the heat and mass transfer of multicom ponent particles to the gas phas
8. DEFINE_SCAT_PHASE_FUNC ScatPhiF2 c fsf real phi 0 real coeffs 9 1 2 00917 1 56339 0 67407 0 22215 0 04725 0 00671 0 00068 0 00005 real P 9 int i fsf 0 P O 1 P 1 c 2 96 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros phi P 0 coeffs 0 P 1 coeffs 1 for i 1 i lt 7 it d P i 1 1 it 1 0 2 i 1 c P i i P i 1 phi coeffs it1 P it 1 return phi DEFINE_SCAT_PHASE_FUNC ScatIso c fsf fsf 0 return 1 0 Hooking a Scattering Phase UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SCAT_PHASE_FUNCTION is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified in the DEFINE macro argument e g ScatPhiB will become visible and selectable in the Create Edit Materials dialog box in ANSYS FLUENT See Section 6 2 17 Hooking DEFINE_SCAT_PHASE_FUNC UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 97 DEFINE Macros 2 3 18 DEFINE_SOLAR_INTENSITY Description You can use the DEFINE_SOLAR_INTENSITY macro to define direct solar intensity or diffuse solar intensity UDFs for the solar load model See Chapter 13 Modeling Heat Transfer in the separate User s Guide for more information on the solar load model Note that solar intensity UDFs are used with the Solar Model which is available only for the 3d geometries in ANSYS FLUENT
9. Figure 6 3 2 The User Defined Function Hooks Dialog Box To hook the UDF to ANSYS FLUENT select the function name e g c_rate libudf in the Cavitation Mass Rate drop down list Figure 6 3 2 and click OK See Section 2 4 1 DEFINE_CAVITATION_RATE for details about DEFINE_CAVITATION_RATE functions 6 56 Release 12 0 ANSYS Inc January 26 2009 6 3 Hooking Multiphase UDFs 6 3 2 Hooking DEFINE EXCHANGE PROPERTY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_EXCHANGE_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in ANSYS FLUENT To hook an exchange property UDF to ANSYS FLUENT first open the Multiphase Model dialog box A Des Edit Customized mass transfer UDFs can be applied to VOF Mixture and Eulerian multi phase models Drag coefficient UDFs can be applied to Mixture and Eulerian models while heat transfer and lift coefficient UDFs can be applied only to the Eulerian model Select the appropriate model from the Model list in the Multiphase Model dialog box and click OK i Make sure that you enable Slip Velocity in the Mixture Parameters group box in the Multiphase Model dialog box in order to display the drag coefficient for the Mixture model Next open the Phase Interaction dialog box Figure 6 3 3 gt R Interaction Phase Interaction
10. Release 12 0 ANSYS Inc January 26 2009 C 6 Eulerian Model Per Phase Turbulence Flow Table C 6 3 DEFINE Macro Usage for the Eulerian Model Per Phase Tur bulence Flow Variable Macro Phase Specified On Wall species boundary condition shear stress components moving velocity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature user defined scalar boundary value discrete phase boundary value DEF INE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE _DPM_BC phase dependent primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity granular conductivity granular solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEFINE PROPERTY DEFINE PROPERTY DEFINE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_TURBULENT_ VISCOSITY secondary phase s secondary phase s secondary
11. define DEFINE_SOURCE name c t dS i real name cell_t c Thread t real dS int i define DEFINE_SOX_RATE name c t Pollut Pollut_Par SOx void name cell_t c Thread t Pollut_Cell Pollut Release 12 0 ANSYS Inc January 26 2009 B 3 DEFINE Macro Definitions Pollut_Parameter Poll_Par SOx_Parameter SOx define DEFINE_SR_RATE name f t r mw yi rr void name face_t f Thread t Reaction r real mw real yi real rr define DEFINE_TURB_PREMIX_SOURCE name c t turbulent_flame_speed source void name cell_t c Thread t real turbulent_flame_speed real source define DEFINE_TURBULENT_VISCOSITY name c t real name cell_t c Thread t define DEFINE_VR_RATE name c t r mw yi rr rr_t void name cell_t c Thread t Reaction r real mw real yi real rr real rr_t define DEFINE_WALL_FUNCTIONS name f t cO tO wf_ret yPlus Emod real name face_t f Thread t cell_t c0 Thread tO int wf_ret real yPlus real Emod B 3 Multiphase DEFINE Macros The following definitions for multiphase DEFINE macros see Section 2 4 Multiphase DEFINE Macros are taken from the udf h header file define DEFINE_CAVITATION_RATE name c t p rhoV rhoL vofV p_v cigma f_gas m_dot void name cell_t c Thread t real p real rhoV real rhoL real vofV real p_v real cigma real f_gas real m_dot define DEFINE_EXCHANGE_PROPERTY name c m
12. return source DEFINE_SOURCE x_sec_recoil cell ts dS eqn real source Thread tm THREAD_SUPER_THREAD ts source C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_U cell ts dS eqn C_R cell ts C_VOF cell ts CURRENT_TIMESTEP return source DEFINE_SOURCE y_prim_recoil cell tp dS eqn real source Thread tm THREAD_SUPER_THREAD tp Thread ts ts THREAD_SUB_THREAD tm 1 source C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_V cell tp dS eqn C_R cell ts C_VOF cell ts CURRENT_TIMESTEP return source DEFINE_SOURCE y_sec_recoil cell ts dS eqn real source Thread tm THREAD_SUPER_THREAD ts source C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_V cell ts dS eqn C_R cell ts C_VOF cell ts CURRENT_TIMESTEP return source 2 1 04 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros DEFINE_SOURCE z_prim_recoil cell tp dS eqn real source Thread tm THREAD_SUPER_THREAD tp Thread ts ts THREAD_SUB_THREAD tm 1 source C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_W cell tp dS eqn C_R cell ts C_VOF cell ts CURRENT_TIMESTEP return source DEFINE_SOURCE z_sec_recoil cell ts dS eqn real source Thread tm THREAD_SUPER_THREAD ts source C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_W cell ts dS eqn C_R cell ts C_VOF cell ts CURRENT_TIMEST
13. A 12 2 Logical Operators Some common logical operators are listed below lt less than lt less than or equal to gt greater than gt greater than or equal to equal to not equal to A 12 Release 12 0 ANSYS Inc January 26 2009 A 13 C Library Functions A 13 C Library Functions C compilers include a library of standard mathematical and I O functions that you can use when you write your UDF code Lists of standard C library functions are presented in the following sections Definitions for standard C library functions can be found in various header files e g global h These header files are all included in the udf h file A 13 1 Trigonometric Functions The trigonometric functions shown below are computed with one exception for the variable x Both the function and the argument are double precision real variables The function acos x is the arccosine of the argument x cos x The function atan2 x y is the arctangent of x y tan t x y The function cosh x is the hyperbolic cosine function etc double acos double x returns the arccosine of x double asin double x returns the arcsine of x double atan double x returns the arctangent of x double atan2 double x double y returns the arctangent of x y double cos double x returns the cosine of x double sin double x returns the sine of x double tan double x returns the tangent of x double cosh double x returns the hy
14. Example FILE fp fprintf fp 12 4e 12 4e 5d n x_array j 0 x_array j 1 noface int datal 64 25 int data2 97 33 fprintf fp 4 2d 4 2d n data1 data2 fscanf int fscanf FILE fp char format The function fscanf reads from a file that is pointed to by fp in a format that you specify The first argument is the format string It specifies how the data that is to be read is to be interpreted The replacement variables that follow the format string are used to store values that are read The replacement variables are preceded by the amp character Note that the format string for fscanf is the same as for fprintf and printf In the example below two floating point numbers are read from the file pointed to by fp and are stored in the variables f1 and f2 Example FILE fp fscanf fp 4f f amp f1 amp f2 i You cannot use the scanf I O function in ANSYS FLUENT You must use fscanf instead A 16 Release 12 0 ANSYS Inc January 26 2009 A 14 Preprocessor Directives A 14 Preprocessor Directives The UDF interpreter supports C preprocessor directives including define and include Macro Substitution Directive Using define When you use the define macro substitution directive the C preprocessor e g cpp performs a simple substitution and expands the occurrence of each argument in macro using the replacement tect define macro replacement text For example the macro
15. Release 12 0 ANSYS Inc January 26 2009 8 71 Examples p Mixture_pressure Temp density yi rho2 MIXTURE_density Temp dT p yi dhdT MIXTURE_enthalpy Temp dT rho2 P yi MIXTURE_enthalpy Temp density P yi dT return dhdT J Kg K double MIXTURE_enthalpy_p double Temp double density double P double yi double dhdp double p double rho2 gt double dp 5 0 p Mixture_pressure Temp density yi rho2 MIXTURE_density Temp p dp yi dhdp MIXTURE_enthalpy Temp rho2 P yi MIXTURE_enthalpy Temp density P yi dp return dhdp J Kg Pascal DORR OO GO E OR Ek k OK IK kkk k kkk k kkk kkk Auxiliary Mixture Functions eect t Tete Te CeCe CL ee CTCL Crorerercrororecrorrrrcrorrrrrererrrrcrr rr sy double Mixture_Rgas double yil double Rgas 0 0 int i for i 0 i lt n_specs i Rgas yili UNIVERSAL_GAS_CONSTANT Mw_i i return Rgas 8 72 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double Mixture_pressure double Temp double Rho double yil double Rgas Mixture_Rgas yi double P Rho Rgas Temp Pressure at Temp amp P return P Kg m73 etree ttt ee TiC tC eet eT EEEE rr rere y Species Property Functions eee et tet ee Te T tC eC CC tCLerCrCrererrcrcrorecreor ore roreorerere terete re y double Mw_i int i double mi 20 mi 0 18 01534 H20 mili 28 013
16. See Section 2 5 13 DEFINE_DPM_SWITCH for details about DEFINE_DPM_SWITCH functions 6 4 14 Hooking DEFINE_DPM_TIMESTEP UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_TIMESTEP UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box Were DEZAIRA Edit Discrete Phase Model Interaction Particle Treatment Interaction with Continuous Phase C Unsteady Particle Tracking C Update DPM Sources Every Flow Iteration Number of Continuous Phase 19 a Iterations per DPM Iteration v Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force ne Number of Scalars a none v 0 i Scalar Update none v Source none v DPM Time Step MATEMATE v Figure 6 4 15 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the UDF tab in the Discrete Phase Model dialog box Select the function name e g limit_to_e_minus_four libudf from the DPM Time Step drop down list under User Defined Functions Figure 6 4 15 and click OK See Section 2 5 14 DEFINE_DPM_TIMESTEP for details about DEFINE_DPM_TIMESTEP func tion
17. for i 0 i lt idim i normal i f_normal i Release 12 0 ANSYS Inc January 26 2009 2 1 57 DEFINE Macros else endif for i 0 i lt idim i normal i f_normal i if p gt type DPM_TYPE_INERT alpha M_PI 2 acos MAX 1 MIN 1 NV_DOT normal P_VEL p MAX NV_MAG P_VEL p DPM_SMALL if NNULLP t amp amp THREAD_TYPE t THREAD_F_WALL F_CENTROID x f t calculate the normal component rescale its magnitude by the coefficient of restitution and subtract the change Compute normal velocity for i 0 i lt idim i vn P_VEL p i normal i Subtract off normal velocity for i 0 i lt idim i P_VEL p i vn normal i Apply tangential coefficient of restitution for i 0 i lt idim i P_VEL p i tan_coeff Add reflected normal velocity for i 0 i lt idim i P_VEL p i nor_coeff vn normal i Store new velocity in P_VELO of particle for i 0 i lt idim i P_VELO p i P_VEL p i return PATH_ACTIVE return PATH_ABORT F 2 1 58 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros Example 2 This example shows how to use DEFINE_DPM_BC for a wall impingement model The function must be executed as a compiled UDF include udf h include dpm h include surf h include random h define a user defined dpm boundary condition routine
18. if gradient not stored yet else BOUNDARY_SECONDARY_GRADIENT_SOURCE Gsource SV_UDSI_G P1 dG es A_by_es 1 gammaO C_UDSI_DIFF c0 t0 P1 alpha0 A_by_es ds betaO Gsource alpha0 aterm alphaO0 gamma0 At Ibw SIGMA_SBC pow WALL_TEMP_OUTER f thread 4 M_PI Specify the radiative heat flux F_PROFILE f thread position aterm Ew Ew aterm 4 M_PI Ibw C_UDSI c0 t0 P1 beta0 end_f_loop f thread DEFINE_HEAT_FLUX heat_flux f t c0 tO cid cir real Ew epsilon_w 2 2 epsilon_w cir 0 Ew F_UDSI f t P1 cir 3 4 0 Ew SIGMA_SBC Release 12 0 ANSYS Inc January 26 2009 8 47 Examples 8 2 6 User Defined Real Gas Models This section contains examples of UDFs that can be used to customize user defined real gas models See Section 8 16 3 The User Defined Real Gas Model in the separate User s Guide for the UDRGM overview limitations and details on how to set up build and load a library of user defined real gas functions UDRGM Example Redlich Kwong Equation of State This section describes another example of a user defined real gas model You can use this example as the basis for your own UDRGM code In this example the Redlich Kwong equation of state is used in the UDRGM This section summarizes the equations used in developing the UDRGM for the Redlich Kwong equation of state The model is based on a modified form of the Redlich Kwong equati
19. C_UDMI c t i 0 0 J end_c_loop c t 2 12 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Hooking an Execute From GUI UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_EXECUTE_FROM_GUI is compiled Chap ter 5 Compiling UDFs the function will not need to be hooked to ANSYS FLUENT through any graphics dialog boxes Instead the function will be searched automatically by the ANSYS FLUENT solver when the execution of the UDF is requested i e when a call is made from a user defined Scheme program to execute a C function 2 2 6 DEFINE_EXECUTE_ON_LOADING Description DEFINE_EXECUTE_ON_LOADING is a general purpose macro that can be used to specify a function that executes as soon as a compiled UDF library is loaded in ANSYS FLUENT This is useful when you want to initialize or setup UDF models when a UDF library is loaded Alternatively if you save your case file when a shared library is loaded then the UDF will execute whenever the case file is subsequently read Compiled UDF libraries are loaded using either the Compiled UDFs or the UDF Library Manager dialog box see Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box An EXECUTE ON LOADING UDF is the best place to reserve user defined scalar UDS and user defined memory UDM for a particular library Sec tions 3 2 8 and 3 2 9 as well as set UDS and UDM names Sections 3 2 8 and 3 2
20. F_CENTROID x f t y x 1 if y lt del F_PROFILE f t i knw y del kinf knvw else F_PROFILE f t i knw h y del kinf knw end_f_loop f t profile for dissipation rate Release 12 0 ANSYS Inc January 26 2009 2 77 DEFINE Macros DEFINE_PROFILE dissip_profile t i real y x ND_ND del h ufree real ff utau knw kinf real mix kay face_t f h YMAX YMIN del DELOVRH h ufree UMEAN B 1 ff 0 045 pow ufree del VISC 0 25 utau sqrt ff pow ufree 2 2 0 knw pow utau 2 sqrt CMU kinf 0 002 pow ufree 2 begin_f_loop f t F_CENTROID x f t y x 1 if y lt del kay knwty del kinf knw else kay knw h y del kinf knw if VKC y lt 0 085 del mix VKC y else mix 0 085 del F_PROFILE f t i pow CMU 0 75 pow kay 1 5 mix end_f_loop f t 2 78 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 3 Fixed Velocity UDF In the following example DEFINE_PROFILE is used to fix flow variables that are held con stant during computation in a cell zone Three separate UDFs named fixed_u fixed_v and fixed_ke are defined in a single C source file They specify fixed velocities that simulate the transient startup of an impeller in an impeller driven mixing tank The physical impeller is simulated by fixing the velocities and turbulence quantities using the fix option in ANSYS FLUENT
21. Figure 6 2 30 The User Defined Functions Dialog Box 6 2 22 Hooking DEFINE_SR_RATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SR_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 31 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first set up an appropriate reaction model in the Species Model dialog box MA sy eres Edit Select Species Transport from the Model list in the Species Model dialog box and enable the Volumetric and Wall Surface options in the Reactions group box Make sure that Stiff Chemistry Solver is disabled in the Options group box and click OK Next open the User Defined Function Hooks dialog box Figure 6 2 31 Release 12 0 ANSYS Inc January 26 2009 6 47 Hooking UDFs to ANSYS FLUENT Define gt User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Net Reaction Rate Volume Reaction Rate nane Surface Reaction Rate apaamamuruuuruap Figure 6 2 31 The User Defined Function Hooks Dialog Box Select the function name e g user_sr_rate libudf in the S
22. Function returns void There are six arguments to DEFINE CG MOTION name dt vel omega time and dtime You supply name the name of the UDF dt vel omega time and dtime are variables that are passed by the ANSYS FLUENT solver to your UDF The linear and angular velocities are returned to ANSYS FLUENT by overwriting the arrays vel and omega respectively Release 12 0 ANSYS Inc January 26 2009 2 209 DEFINE Macros Example Consider the following example where the linear velocity is computed from a simple force balance on the body in the x direction such that I dv elm dt 2 6 1 where v is velocity F is the force and m is the mass of the body The velocity at time t is calculated using an explicit Euler formula as Ut vat F m At 2 6 2 POR CCA AAR A GAARA RI A A A 1 1 1 2K kkk k 4 4 4 k x 1 degree of freedom equation of motion x direction compiled UDF BRERA AAR ARIA I I A A 2k KK 1 2K 21 21 A A 4 24 1 1 1 KK k kk kkk include udf h static real v_prev 0 0 DEFINE_CG_MOTION piston dt vel omega time dtime Thread t face_t f real NV_VEC A real force dv reset velocities NV_S vel 0 0 NV_S omega 0 0 if Data_Valid_P return get the thread pointer for which this motion is defined t DT_THREAD dt compute pressure force on body by looping through all faces force 0 0 begin_f_loop f t d F_AREA A f t force F_P f t NV_MA
23. Release 12 0 ANSYS Inc January 26 2009 2 1 23 DEFINE Macros Hooking a Turbulent Premixed Source UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_TURB_PREMIX_SOURCE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g turb_flame_src will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 24 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs for details 2 3 25 DEFINE_TURB_SCHMIDT UDF The DEFINE_TURB_SCHMIDT macro can be used to specify the turbulent Schmidt numbers of all transported species in ANSYS FLUENT for single phase flows Description The turbulent Schmidt number denoted Sc controls the turbulent diffusion of species transported in ANSYS FLUENT You can use DEFINE_TURB_SCHMIDT to specify Sc for each species solved Usage DEFINE_TURB_SCHMIDT name c t i Argument Type Description symbol name UDF name cellt c Index of cell on which the Turbulent Schmidt number function is to be applied Thread t Pointer to cell thread int i Species index Function returns real There are four arguments to DEFINE_TURB_SCHMIDT name c t and i You supply name the name of the UDF c t and i are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the turbulent Schmid
24. UDM_UNRESERVED Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_UDM libname else Message d UDMs have been reserved by the current library s n NUM_UDM libname 3 52 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Set_User_Memory_Name udm_offset lib1 UDM 0 Set_User_Memory_Name udm_offsett 1 lib1 UDM 1 Set_User_Memory_Name udm_offset 2 lib1 UDM 2 Message nUDM Offset for Current Loaded Library d udm_offset DEF INE_ON_DEMAND set_udms Domain d Thread x ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n for i 0 i lt NUM_UDM i thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 3 0 i 10 0 end_c_loop c ct else Message UDMs have not yet been reserved for library 1 n Release 12 0 ANSYS Inc January 26 2009 3 53 Additional Macros for Writing UDFs Example 2 BER AAA I I CRIA AR I A A A A 1 11 1 21 21 2 A A 21 21 21 1 kkk kk kkk kkk kkk udm_res2 c contains two UDFs an execute on loading UDF that reserves two UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs BOO OO RR a Ra kK ak kk ak kk include udf h define NUM_UDM 2 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname
25. s and the Jacobian array jac The Jacobian is only required for surface chemistry and is the derivative of the surface net reaction rate with respect to the species concentration DEFINE NET REACTION RATE is called for all fluid zones volumetric reactions as well as surface reactions in porous media and for all wall thread zones whenever the Reaction option is enabled in the boundary conditions dialog box and the UDF is hooked to ANSYS FLUENT in the User Defined Function Hooks dialog box i DEFINE_NET_REACTION_RATE functions can be executed only as compiled UDFs Example The following UDF named net_rxn assumes that the net volumetric reaction rate is the expression Rnet 1 Nspe Y 2 3 7 where Nspe is the number of species POR oo o o kk A A 11 21 21 21 kk k kkk Net Reaction Rate Example UDF BEAR oo oo o kkk kk k kkk kkk include udf h DEFINE_NET_REACTION_RATE net_rxn c t particle pressure temp yi rr jac int i for i 0 i lt n_spe i rr i 1 real n_spe yi i Note that during the coarse of the ODE solution the species mass fractions can exceed realizable bounds For optimal ODE performance the species mass fractions should not be clipped but derived quantities such as concentrations which are raised to non integer powers must be bounded Also if density is required for instance to calculate concentrations it should be calculated from the temperature and species passed into the UDF Finall
26. save current fluid viscosity for start of next step P_USER_REAL p 1 c gt mu write melting index when sorting particles at surfaces DEF INE_DPM_OUTPUT melting_output header fp p thread plane char name 100 if header Release 12 0 ANSYS Inc January 26 2009 2 1 91 DEFINE Macros if NNULLP thread par_fprintf_head fp s d n THREAD_HEAD thread gt dpm_summary sort_file_name 11 else par_fprintf_head fp s d n plane gt sort_file_name 11 par_fprintf_head fp 10s 10s 10s 10s 10s 10s 10s 10s 10s 10s 10s s n ug nyn ug ge nyn ny diameter T mass flow time melt index name sprintf name s d P_INJECTION p gt name p gt part_id add P_INJ_ID P_INJECTION p and part_id for sorting in parallel par_fprintf fp hd hd 10 6g 10 6g 10 6g 10 6g 10 6g 10 6g Z10 6g 10 6g 10 6g 10 6g 10 6g s n P_INJ_ID P_INJECTION p p gt part_id P_POS p 0 P_POS p 1 P_POS p 2 P_VEL p 0 P_VEL p 1 P_VEL p 2 P_DIAM p P_T p P_FLOW_RATE p P_TIME p P_USER_REAL p 0 name Hooking a DPM Scalar Update UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DPM SCALAR UPDATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Mode
27. ANSYS Inc January 26 2009 2 211 DEFINE Macros Usage DEFINE DYNAMIC_ZONE_PROPERTY name dt swirl_center Argument Type Description symbol name UDF name Dynamic_Thread dt Pointer to a structure that stores the dynamic mesh attributes This is set to NULL internally as there are no dynamic zones in the current calculation of swirl center real swirl_center Pointer to a real array of 3 dimension You will assign this value in the UDF The x y and z values of the swirl_center can be assigned in the UDF through swirl_center 0 swirl_center 1 and swirl_center 2 respectively Function returns void There are three arguments to DEFINE_DYNAMIC_ZONE_PROPERTY name dt and swirl_center You supply name the name of the UDF and pointer to a real array swirl_center dt is a variable that is passed by the ANSYS FLUENT solver to your UDF Example UDF hook for calculating Swirl Center while computing In Cylinder specific output Arguments for the UDF hook are name of the UDF dt dynamic thread which is set to NULL and it is not supposed to be manipulated in the UDF as there are no dynamic zones in the current context and swirl center which is to be calculated in the UDF Works in parallel as well include udf h define RPM RP_Get_Real dynamesh in cyn crank rpm static real Zmin_at_TDC 0 0014 Piston location at TDC static real Zmax 0 0145 Zmax a fixed point static void my_swirl_c
28. ANSYS Inc January 26 2009 3 11 Additional Macros for Writing UDFs Message0 show grad Reconstruction Gradient of V is available n if NNULLP THREAD_STORAGE t SV_W_RG Message0 show grad Reconstruction Gradient of W is available n if NNULLP THREAD_STORAGE t SV_T_RG Message0 show grad Reconstruction Gradient of T is available n if NNULLP THREAD_STORAGE t SV_H_RG Message0 show grad Reconstruction Gradient of H is available n if NNULLP THREAD_STORAGE t SV_K_RG Message0 show grad Reconstruction Gradient of K is available n if NNULLP THREAD_STORAGE t SV_D_RG Message0 show grad Reconstruction Gradient of D is available n if NNULLP THREAD_STORAGE t SV_O_RG Message0 show grad Reconstruction Gradient of 0 is available n if NNULLP THREAD_STORAGE t SV_NUT_RG Message0 show grad Reconstruction Gradient of NUT is available n if nspe int ns 0 spe_loop ns nspm 3 12 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros if NNULLP THREAD_STORAGE t SV_Y_I ns SV_Y_O_RG SV_Y_O Message0 show grad Reconstruction Gradient of Species d is available n ns CCRC COO OOO 2K ak 3K 2K K FK OR K 2K 2K K FK 2K 2K 2K FK 2K K FK FK 2K K FK 2K 2K OK FK KK K 2 2k 2k KKK K K PCR COO kak 3k 2k OO RO 3K 2K K FK 2K 2K K FK 2K K K I K FK 2K KK FK FKK K FK KK K 2 2k
29. Description You can use DEFINE_DOM_SPECULAR_REFLECTIVITY to modify the inter facial reflectivity of specularly reflecting semi transparent walls You may wish to do this if the reflectivity is dependent on other conditions that the standard boundary condition doesn t allow for see Section 5 3 6 Specular Semi Transparent Walls in the separate Theory Guide for more information During ANSYS FLUENT execution the same UDF is called for all the faces of the semi transparent wall for each of the directions Usage DEF INE_DOM_SPECULAR_REFLECTIVITY name f t nband n_a n_b ray_direction en internal_reflection specular_reflectivity specular_transmissivity Release 12 0 ANSYS Inc January 26 2009 2 39 DEFINE Macros Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name face_t f Face index Thread t Pointer to face thread on which the specular reflectivity function is to be applied int nband Band number needed for non gray discrete ordinates DO model real na Refractive index of medium a real nb Refractive index of medium b real ray_direction Direction vector s defined in Equation 5 3 55 in the separate Theory Guide real en Interface normal vector n defined in Equation 5 3 55 in the separate Theory Guide int internal_reflection Variable
30. Domain d Thread ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n for i 0 i lt NUM_UDM i thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 3 0 i 10 0 end_c_loop c ct else Release 12 0 ANSYS Inc January 26 2009 2 15 DEFINE Macros Message UDMs have not yet been reserved for library 1 n Hooking an Execute On Loading UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_EXECUTE_ON_LOADING is compiled Chapter 5 Compiling UDFs the function will not need to be hooked to ANSYS FLUENT through any graphics dialog boxes Instead ANSYS FLUENT searches the newly loaded library for any UDFs of the type EXECUTE_ON_LOADING and will automatically execute them in the order they appear in the library 2 2 7 DEFINE EXECUTE AFTER CASE DATA Description DEFINE_EXECUTE_AFTER_CASE and DEFINE_EXECUTE_AFTER_DATA are general purpose macros that can be used to specify a function that executes after the case and or data file is read in ANSYS FLUENT This is useful because it provides access to UDF functions after the case and or data file is read Compiled UDF libraries are loaded using either the Compiled UDFs or the UDF Library Manager dialog box see Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box DEFINE_EXECUTE_AFTER_CASE and DEFINE_EXECUTE_AFTER_DATA UDFs can be executed only as co
31. There are four arguments to the message passing macros For send messages the argument to is the node ID of the process that data is being sent to buffer is the name of an array of the appropriate type that will be sent nelem is the number of elements in the array and tag is a user defined message tag The tag convention is to use myid when sending messages For receive messages the argument from is the ID of the sending node buffer is the name of an array of the appropriate type that will be received nelem is the number of elements in the array tag is the ID of the sending node as the convention is to have the tag argument the same as the from argument i e the first argument for receive messages Release 12 0 ANSYS Inc January 26 2009 7 29 Parallel Considerations Note that if variables that are to be sent or received are defined in your function as real variables then you can use the message passing macros with the _REAL suffix The compiler will then substitute PRF_CSEND_DOUBLE or PRF_CRECV_DOUBLE if you are running double precision and PRF_CSEND_FLOAT or PRF_CRECV_FLOAT for single precision Because message passing macros are low level macros you will need to make sure that when a message is sent from a node process a corresponding receiving macro appears in the receiving node process Note that your UDF cannot directly send messages from a compute node other than 0 to the host using message passing mac
32. User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data mor Execute at Exit Wall Heat Flux Figure 6 1 4 The User Defined Function Hooks Dialog Box Click the Edit button next to Execute At End to open the Execute At End Functions dialog box Figure 6 1 5 Release 12 0 ANSYS Inc January 26 2009 6 5 Hooking UDFs to ANSYS FLUENT Execute at End Functions Available Execute at End Functions E E Selected Execute at End Functions E amp J l execute_at_end2 libudf execute_at_end1 libudf Figure 6 1 5 The Execute At End Functions Dialog Box Select the function s you wish to hook to your model from the Available Execute at End Functions list Click Add and then OK to close the dialog box The name of the function you selected will be displayed in the Execute at End field of the User Defined Function Hooks dialog box If you select more than one function the number will be displayed e g 2 selected Click OK in the User Defined Function Hooks dialog box to apply the settings See Section 2 2 3 DEFINE_EXECUTE_AT_END for details about defining DEFINE_EXECUTE_AT_END functions 6 1 4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs
33. if udm_offset UDM_UNRESERVED udm_offset Reserve_User_Memory_Vars NUM_UDM if udm_offset UDM_UNRESERVED Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_UDM libname else Message d UDMs have been reserved by the current library s n NUM_UDM libname Set_User_Memory_Name udm_offset lib2 UDM 0 Set_User_Memory_Name udm_offsett 1 lib2 UDM 1 Message nUDM Offset for Current Loaded Library d udm_offset DEF INE_ON_DEMAND set_udms Domain d Thread ct cell_t c int i d Get_Domain 1 if udm_offset UDM_UNRESERVED Message Setting UDMs n 3 54 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros for i 0 i lt NUM_UDM i thread_loop_c ct d begin_c_loop c ct C_UDMI c ct udm_offset i 2 0 1i 10 0 end_c_loop c ct J else Message UDMs have not yet been reserved for library 1 n If your model uses a number of UDMs it may be useful to define your variables in an easy to read format either at the top of the source file or in a separate header file using the preprocessor define directive define C_MAG_X c t C_UDMI c t udm_offset define C_MAG_Y c t C_UDMI c t udm_offset 1 Following this definition in the remainder of your UDF you can simply use C_MAG_X c t and C_MAG_Y c t to specify the fixed magnetic field components Unreserving UDM variables ANSYS
34. out libudf dl 1 udf_names obj udfexample obj 11209s 1ib Microsoft R Incremental Linker Version 7 10 3077 Copyright C Microsoft Corporation All rights reserved Creating library libudf 1lib and object libudf exp C Program Files ANSYS Inc v120 fluent ntbin ntx86 libudf ntx86 2d gt Note that if there are problems with the build you can do a complete rebuild by typing nmake clean and then nmake again Release 12 0 ANSYS Inc January 26 2009 5 15 Compiling UDFs UNIX and Linux Systems 1 Using a text editor edit the file makefile in your src directory to set the following two parameters SOURCES and FLUENT_INC SOURCES the name of your source file s e g udfexample c Multiple sources can be specified by using a space delimiter e g udfexample1 c udfexample2 c FLUENT_INC the path to your release directory 2 If your architecture is irix6 5 make the following additional change to the makefile a Find the following line in the makefile CFLAGS_IRIX6R10 KPIC ansi fullwarn 0 n32 b Change ansi to xansi CFLAGS_IRIX6R10 KPIC xansi fullwarn 0 n32 For all other architectures do not make any further changes to the makefile An excerpt from a sample makefile is shown below Heron E e makefile for user defined functions He a SS a es SSS re ee User modifiable section Heron nnn SOURCES udfexamplel c FLUENT_INC path ansys_inc v120 fluent Precompiled
35. sqrt urelx urelx urely urely urelz urelz relative velocity Re urel diam C_R c tp C_MU_L c tp Sc C_MU_L c tp C_R c tp D_evap_prim Nu 2 0 6 pow Re 0 5 pow Sc 0 333 mass_coeff Nu D_evap_prim diam for i 0 i lt MAX_SPE_EQNS_PRIM i 4 accum accum C_YI c tp i mw i prim_index mole_frac_evap_prim C_YI c tp index_evap_primary mw index_evap_primary prim_index accum concentration_evap_primary mole_frac_evap_prim P_OPER UNIVERSAL_GAS_CONSTANT T_prim concentration_sat psat_h2o T_sec UNIVERSAL_GAS_CONSTANT T_sec area_density 6 C_VOF c ts diam flux_evap mass_coeff concentration_sat concentration_evap_primary rr area_density flux_evap Hooking a Heterogeneous Reaction Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_HET_RXN_RATE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the ar gument that you supplied as the first DEFINE macro argument e g user_evap_condens_react will become visible and selectable under Reaction Rate Function in the Reactions tab of the Phase Interaction dialog box Note you will first need to specify the Total Number of Reactions greater than 0 See Section 6 3 3 Hooking DEFINE HET RXN_RATE UDFs for details 2 1 48 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros 2 4 4
36. symbol name UDF name cellt c Cell index Thread t Cell thread mixture level on which heterogeneous reaction rate is to be applied Hetero Reaction r Pointer to data structure that represents the current heterogeneous reaction see sg_mphase h real mw MAX PHASES MAX_SPE_EQNS Matrix of species molecular weights mw i j will give molecular weight of species with ID j in phase with index i For phase which has fluid material the molecular weight can be accessed as mw i 0 real yi MAX_PHASES MAX_SPE_EQNS Matrix of species mass fractions yi i j will give mass fraction of species with ID j in phase with index i For phase which has fluid material yi i 0 will be 1 real rr Pointer to laminar reaction rate real rr_t Currently not used Provided for future use Function returns void There are eight arguments to DEFINE HET RXN_RATE name c t r mw yi rr and rrt You supply name the name of the UDF c t r mw yi rr and rr_t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointer rr The values must be specified in emnol m where the volume is the cell volume Example The following compiled UDF named user_evap_condens_react defines the reaction rate required to simulate evaporation or condensation on the surface of droplets Such a reaction can be formally described by the following HO tig gt H20 e
37. vw Reynolds stress C_RUW c t cell_t c Thread t uw Reynolds stress Release 12 0 ANSYS Inc January 26 2009 3 21 Additional Macros for Writing UDFs VOF Multiphase Model Macro The macro C_VOF can be used to return real variables associated with the VOF mul tiphase model in SI units The variables are available in both the pressure based and the density based solver with the exception of the VOF variable which is available only for the pressure based solver Definitions for these macros can be found in sg mphase h which is included in udf h Table 3 2 19 Macros for Multiphase Variables Defined in sg mphase h Macro Argument Types Returns C_VOF c t cell_t c Thread t volume fraction for the has to be a phase phase corresponding to phase thread thread t 3 2 4 Face Macros The macros listed in Table 3 2 20 3 2 23 can be used to return real face variables in SI units They are identified by the F_ prefix Note that these variables are available only in the pressure based solver In addition quantities that are returned are available only if the corresponding physical model is active For example species mass fraction is available only if species transport has been enabled in the Species Model dialog box in ANSYS FLUENT Definitions for these macros can be found in the referenced header files e g mem h Face Centroid F CENTROID The macro listed in Table 3 2 20 can
38. 0 Rule Figure 3 2 1 ANSYS FLUENT Determination of Face Area Normal Direction 2D Face ANSYS FLUENT assigns adjacent cells to an interior face cO and c1 according to the following convention the cell out of which a face area normal is pointing is designated as cell CO while the cell in to which a face area normal is pointing is cell c1 Figure 3 2 1 In other words face area normals always point from cell cO to cell c1 Release 12 0 ANSYS Inc January 26 2009 3 23 Additional Macros for Writing UDFs Flow Variable Macros for Boundary Faces The macros listed in Table 3 2 22 access flow variables at a boundary face Table 3 2 22 Macros for Boundary Face Flow Variables Defined in mem h Macro Argument Types Returns F_U f t face_t f Thread t u velocity F_V f t face_t f Thread t v velocity F_W f t face_t f Thread t w velocity F_T f t facet f Thread t temperature FH f t face t f Thread t enthalpy F_K f t face_t f Thread t turbulent kinetic energy F_D f t face_t f Thread t turbulent kinetic energy dissipation rate FYI f t i face_t f Thread t int i species mass fraction See Section 2 7 3 DEFINE UDS FLUX for an example UDF that utilizes some of these macros Flow Variable Macros at Interior and Boundary Faces The macros listed in Table 3 2 23 access flow variables at interior faces and boundary faces Table 3 2 23 Macros for Interior and Boundary Face Flo
39. 2 gt gt Secondary phase domain domain_id 3 Secondary phase domain domain_id 4 Phase level threads for inlet zone identified by phase_domain_index Figure 1 10 1 Domain and Thread Structure Hierarchy Figure 1 10 1 introduces the concept of the domain_id and phase_domain_index The domain_id can be used in UDFs to distinguish the superdomain from the primary and secondary phase level domains The superdomain mixture domain domain_id is always assigned the value of 1 Interaction domains are also identified with the domain_id The domain_ids are not necessarily ordered sequentially as shown in Figure 1 10 1 The phase_domain_index can be used in UDFs to distinguish between the primary and secondary phase level threads phase_domain_index is always assigned the value of 0 for the primary phase level thread The data structures that are passed to a UDF depend on the multiphase model that is enabled the property or term that is being modified the DEFINE macro that is used and the domain that is to be affected mixture or phase To better understand this consider the differences between the Mixture and Eulerian multiphase models In the Mixture model a single momentum equation is solved for a mixture whose properties are determined from the sum of its phases In the Eulerian model a momentum equation is solved for each phase ANSYS FLUENT allows you to directly specify a momentum source
40. 2 125 log file 4 5 logical operators A 12 looking up a thread pointer 3 29 Index 9 Index Lookup_Thread 1 11 3 29 7 40 looping macros for multiphase applications 3 60 for parallel 7 22 general purpose 3 56 looping over cell threads in domain 3 56 cells in thread 3 57 exterior cells parallel 7 23 face threads in domain 3 56 faces in thread 3 57 faces of cell 3 58 interior cells parallel 7 22 nodes of cell 3 59 nodes of face 3 59 MPI 2 60 2 61 2 159 2 197 3 82 macro substitution A 17 macros see also DEFINE macros 1 4 adjacent cell index 3 26 adjacent cell thread 3 27 ANSYS FLUENT variables accessing 3 1 area normal vector 3 27 axisymmetric considerations 3 4 cell face 3 7 cell face index 3 7 cell face thread 3 7 cell thermodynamic properties 3 19 cell variable 3 6 cell volume 3 6 centroid variables 3 6 3 22 data access 3 1 derivative variable 3 17 DPM variable 3 36 dynamic mesh 3 43 error 3 79 face area vector 3 23 face variable 3 5 3 7 3 22 flow variable 3 8 3 24 gradient vector 3 8 input output 3 1 Index 10 looping 3 1 general purpose 3 56 multiphase specific 3 60 material property 3 18 message 3 79 miscellaneous 3 1 multiphase variables 3 22 node coordinates 3 5 node variable 3 5 3 7 NOx 3 40 particle variable 3 36 previous time step 3 16 reconstruction gradient vector 3 8 Reynolds Stress Model 3 21 scheme 3 1 S
41. 2 190 A 15 profile UDFs external emissivity 2 72 heat generation rate 2 72 inertial resistance 2 72 porosity 2 72 porous resistance 2 72 species mass fraction 2 72 specific dissipation rate 2 72 stress condition 2 72 temperature 2 72 turbulence dissipation rate 2 72 turbulence kinetic energy 2 72 velocity 2 72 viscous resistance 2 72 volume fraction 2 72 wall shear 2 72 PROP ktc 2 89 PROP_mu 2 89 PROP_rho 2 89 property UDFs absorption and scattering coefficient 2 87 density 2 87 diameter 2 87 elasticity modulus 2 87 example 8 30 for DPM 2 186 frictional pressure 2 87 frictional viscosity 2 87 general 2 87 granular conductivity 2 87 viscosity 2 87 radial distribution 2 87 rate of strain 2 87 six degrees of freedom solver 2 221 solids pressure 2 87 Index 14 thermal conductivity 2 87 user defined mixing laws conductivity 2 87 density 2 87 viscosity 2 87 viscosity 2 87 radiation scattering phase function 2 95 radiative transport equation 2 39 rate of strain 2 87 reaction rate UDFs examples 8 35 heterogeneous 2 144 particle 2 58 species net 2 50 surface 2 114 volumetric 2 129 read write UDFs 2 23 reader 2 23 real gas model UDFs examples 8 48 real gas models UDRGM example 8 48 8 65 8 75 reconstruction gradient macros 3 8 Reynolds Stress Model macros 3 21 RP macros 3 75 RP_CELL 2 177 2 195 2 197 RP_Get_Integer 3 78 7 39 RP_HOST 7 13
42. 3 59 3 60 node pointer 3 2 node variable macros 3 7 node_to_host 7 16 NODE_X 2 219 nodes 1 10 non gray discrete ordinates model UDFs emissivity weighting factor 2 41 gray band coefficient 2 43 NOx macros 3 40 NOx Model dialog box 6 28 NOx rate UDFs 2 52 6 28 NULLIDX 3 40 3 41 NULLP 2 190 3 81 number of faces in cell macro for 3 7 number of nodes in face macro for 3 7 NV_CROSS 2 219 NV_D 2 219 2 232 NV_DOT 2 40 2 156 2 159 NV_MAG 2 115 2 117 2 143 2 156 2 159 3 72 7 9 NV_MAG2 3 72 NV S 2 210 2 219 2 232 NVV 2 122 2 219 3 71 NV VVS 3 71 NV VEC 2 143 2 156 2 210 2 219 2 232 NV_VS 2 168 NV_VS_VS 3 72 NV VV 2 219 3 71 object code 1 6 on demand UDFs 2 20 3 10 ONE_COMPUTE_NODE_P 7 17 P 1 radiation model UDF 8 43 P_CELL 2 177 2 197 3 37 P_CELL_THREAD 2 177 2 197 3 37 P_CURRENT_LAW 2 197 3 37 P_DEVOL_SPECIES_INDEX 3 37 P_DIAM 2 60 2 61 2 159 2 177 2 182 3 36 P_DIAMO 3 37 P_DT 2 190 2 197 3 36 P_EVAP_SPECIES_INDEX 3 37 P_FLOW_RATE 2 177 3 36 Index 12 P_INIT_DIAM 2 182 2 195 3 37 P_INIT_LF 3 37 P_INIT_MASS 2 60 2 61 2 187 3 37 P_INIT_POS 3 37 P_INIT_RHO 3 37 P_INIT_TEMP 3 37 P_INIT_VEL 3 37 P_LF 3 36 P_LFO 3 37 P_MASS 2 61 2 164 2 168 2 177 2 182 2 187 2 197 3 36 P_MASSO 3 37 P_MATERIAL 2 197 3 37 P_NEXT_LAW 3 37 P_OXID_SPECIES_INDEX 3 37 P_POS 3 36 P_POSO 3 37 P_PROD_SPECIES_INDEX 3
43. ANSYS Inc January 26 2009 8 77 Examples DEF INE_ON_DEMAND I_do_nothing This is a dummy function must be included to allow for the use of the ANSYS FLUENT UDF compilation utility void Mixture_error int err char f char msg if err usersError Mixture_error d from function s n s n err f msg DCO OOO OO GAR ASI I A A Ak 2k 2k 2k 2k 2k ak Mixture Functions These are the only functions called from ANSYS FLUENT Code POR ooo ooo o o kkk A A kkk kk k kkk void MIXTURE_Setup Domain domain cxboolean vapor_phase char specielist int messagefunc char format void errorfunc char format 1 This function will be called from ANSYS FLUENT after the UDF library has been loaded User must enter the number of species in the mixture and the name of the individual species int i usersMessage messagefunc usersError errorfunc ref_p ABS_P RP_Get_Real reference pressure op_pres ref_T 298 15 Message0 n MIXTURE_Setup Redlich Kwong equation of State with ideal gas mixing rules n Message0 n MIXTURE_Setup reference temperature is f n ref_T if ref_p 0 0 MessageO n MIXTURE_Setup reference pressure was not set by user n Message0 n MIXTURE_Setup setting reference pressure to 101325 Pa n 8 78 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples ref_p 101325 0 Jesssyy
44. Argument Type Description symbol name UDF name Domain d Pointer to domain Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by ANSYS FLUENT real position Pointer to array that stores the position Function returns void 2 216 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros There are four arguments to DEFINE_GEOM name d dt and position You supply name the name of the UDF d dt and position are variables that are passed by the ANSYS FLUENT solver to your UDF The new position after projection to the geometry defining the zone is returned to ANSYS FLUENT by overwriting the position array Example The following UDF named parabola is executed as a compiled UDF DCO OOOO AA aKa I a A Kk defining parabola through points 0 1 1 2 5 4 1 1 FEO AAIIIR I k k a a kk include udf h DEFINE_GEOM parabola domain dt position set y x 2 x 1 position 1 position 0 position 0 position 0 1 J Hooking a Dynamic Mesh Geometry UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE GEOM is compiled see Chapter 5 Com piling UDFs for details the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Mesh Zones dialog box in ANSYS FLUENT See Section 6 5 3 Hooking DEFINE_GEOM UDFs for details on how to hook
45. Click Create and then Close See Section 2 6 3 DEFINE_GEOM for details about DEFINE_GEOM functions Release 12 0 ANSYS Inc January 26 2009 6 85 Hooking UDFs to ANSYS FLUENT Dynamic Mesh Zones cuit default interior parabola libudf Figure 6 5 4 The Dynamic Mesh Zones Dialog Box 6 86 Release 12 0 ANSYS Inc January 26 2009 6 5 Hooking Dynamic Mesh UDFs 6 5 4 Hooking DEFINE_GRID_MOTION UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_GRID_MOTION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones dialog box Figure 6 5 5 To hook the UDF to ANSYS FLUENT you will first need to enable the Dynamic Mesh option in the Dynamic Mesh task page DaN Dynamic Mesh Next open the Dynamic Mesh Zones dialog box DAE Create Edit Dynamic Mesh Zones Zone Names Dynamic Mesh Zones axis inlet wv axis inlet default interior Type O Stationary O Rigid Body O Deforming User Defined Motion Attributes Geometry Definition Meshing Options Mesh Motion UDF beam slibudF v i Figure 6 5 5 Dynamic Mesh Zones Select User Defined under Type in the Dynamic Mesh Zones dialog box Figure 6 5 5 and click the Motion Attributes tab Select the function name e g beam libudf
46. DEFINE SDOF PROPERTIES Table 2 6 1 Quick Reference Guide for Dynamic Mesh Specific DEFINE Macros Function DEFINE Macro Dialog Box Activated In center of gravity motion DEFINE CG MOTION Dynamic Mesh Zones swirl center DEFINE_DYNAMIC_ZONE_PROPERTY In Cylinder Output Controls varying cell layering height DEFINE_DYNAMIC_ZONE_PROPERTY Dynamic Mesh Zones mesh motion DEFINE GRID MOTION Dynamic Mesh Zones geometry deformation DEFINE GEOM Dynamic Mesh Zones properties for Six Degrees of DEFINE_SDOF_PROPERTIES Dynamic Mesh Zones Freedom SDOF Solver 2 208 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros 2 6 1 DEFINE_CG_MOTION Description You can use DEFINE CG MOTION to specify the motion of a particular dynamic zone in ANSYS FLUENT by providing ANSYS FLUENT with the linear and angular velocities at every time step ANSYS FLUENT uses these velocities to update the node positions on the dynamic zone based on solid body motion Note that UDFs that are defined using DEFINE_CG_MOTION can only be executed as compiled UDFs Usage DEFINE_CG_MOTION name dt vel omega time dtime Argument Type Description symbol name UDF name Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by ANSYS FLUENT real vel Linear velocity real omegal Angular velocity real time Current time real dtime Time step
47. DEFINE_UDS_FLUX UDFs defining 2 230 hooking to ANSYS FLUENT 6 93 Index 5 Index DEFINE_UDS_UNSTEADY UDFs defining 2 234 hooking to ANSYS FLUENT 6 94 DEFINE_VECTOR_EXCHANGE_PROPERTY UDF s defining 2 151 hooking to ANSYS FLUENT 6 61 DEFINE_VR_RATE UDFs defining 2 129 example 8 38 hooking to ANSYS FLUENT 6 53 DEFINE_WALL_FUNCTIONS UDFs defining 2 133 hooking to ANSYS FLUENT 6 54 defining UDFs 8 2 using DEFINE macros 2 1 deforming zone geometry UDFs 2 216 demo_calc 2 23 density UDF 6 38 derivative variable macros 3 17 derivatives source term 2 101 diffuse reflectivity UDFs 2 36 diffusion coefficient 3 25 diffusive flux 3 25 diffusivity 1 3 diffusivity coefficient UDFs 2 225 dimension utilities 3 69 directory structure UNIX systems 5 12 Windows systems 5 10 discrete ordinates model UDFs diffuse reflectivity 2 36 emissivity weighting factor 2 41 gray band coefficient 2 43 non gray emissivity weighting factor 2 41 gray band coefficient 2 43 scattering phase 2 95 source terms 2 38 specular reflectivity 2 39 Discrete Phase Model dialog box 6 65 6 67 6 75 6 76 discrete phase model UDF s body force 2 163 Index 6 boundary conditions 2 156 defining 2 154 drag coefficient 2 165 erosion and accretion rates 2 167 for sampling device output 2 183 for switching custom laws 2 196 for time step control 2 202 heat and mass transfer 2 173 hooking to ANSYS FLUENT 6 63 partic
48. If you select Specified Flux in the User Defined Scalar Boundary Condition group box for a particular UDS then your input will be the value of the flux at the boundary i e the dot product of the negative of the term in parentheses on the left hand side of Equation 1 3 2 in the separate Theory Guide with the vector that is normal to the domain if you instead select Specified Value then your input will be the value of the scalar itself at the boundary In the sample dialog box shown previously for example the Specified Value for User Scalar 0 is set to a user_scalar UDF Release 12 0 ANSYS Inc January 26 2009 6 35 Hooking UDFs to ANSYS FLUENT Note that for interior walls you will need to select Coupled Boundary if the scalars are to be solved on both sides of a two sided wall Note that the Coupled Boundary option will show up only in the drop down list when all zones is selected for Solution Zones in the User Defined Scalars dialog box In some cases you may wish to exclude diffusion of the scalar at the inlet of your domain You can do this by disabling Inlet Diffusion for the scalar in the User Defined Scalars dialog box See Section 2 3 15 DEFINE_PROFILE for details about DEFINE_PROFILE functions 6 2 16 Hooking DEFINE_PROPERTY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your material property UDF the name of the function you supplied as a DEFINE macro a
49. Inc January 26 2009 6 2 Hooking Model Specific UDFs If you are using your UDF to specify a fixed value in a cell zone you will need to turn on the Fixed Values option in the Fluid or Solid dialog box Then click the Fixed Values tab and select the name of the UDF in the appropriate drop down list for the value you wish to set See Section 2 3 15 DEFINE_PROFILE for details about DEFINE_PROFILE functions Hooking Profiles for UDS Equations For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can hook a fixed value UDF for a cell zone e g Fluid or Solid and a specified value or flux UDF for all wall inflow and outflow boundaries After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_PROFILE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the appropriate boundary or cell zone condition dialog box in ANSYS FLUENT To open the boundary or cell zone condition dialog box select the zone in the Boundary Conditions or Cell Zone Conditions task page and click the Edit button gt Eire mecnchicnt or gt Cell Zone Conditions e If you are using your UDF to specify a fixed value in a cell zone you will need to enable the Fixed Values option in the Fluid or Solid dialog box Then click the Fixed Values tab Figure 6 2 18 and select the na
50. Inc January 26 2009 user defined memory variable example 3 49 for cells 3 49 for faces 3 48 user defined real gas model UDRGM examples 8 48 multiple species real gas model 8 65 Redlich Kwong equation example 8 48 volumetric reactions 8 75 user defined scalar transport equations examples 2 225 8 40 source term UDF 2 100 user defined scalar variable example 3 49 for cells 3 45 for faces 3 45 User Defined Scalars dialog box 6 93 6 94 user_nt udf 5 13 comuser nt udf 5 10 utilities dimension 3 69 vector 3 69 vapor pressure UDF 2 186 vaporization temperature UDF 2 186 variable cell layering height UDFs defining 2 214 hooking to ANSYS FLUENT 6 84 Variable Time Step Setting dialog box 6 4 variables dynamic mesh 3 43 vector cross products 3 73 vector dot products 3 73 vector exchange property UDFs 2 151 vector utilities 3 69 Velocity Inlet dialog box 6 32 8 11 8 17 velocity inlet parabolic profile UDF 8 14 viscosity property UDF 8 30 Viscous Model dialog box 6 31 6 49 6 51 6 52 Index 17 Index VOF model DEFINE macro usage C 1 volume reaction rate 1 3 volume reaction rate UDFs 2 129 Wall dialog box 6 35 wall function UDFs 2 133 wall heat flux UDFs 2 45 wall impacts 2 167 wall inflow and outflow boundary condition UDFs 2 227 Windows systems 2 23 folder structure 5 10 working folder 4 2 5 3 writer 2 23 writing files parallel 7 40 writing UDFs for multipha
51. Interaction Particle Treatment C Interaction with Continuous Phase Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force particle_body_force Tt v Number of Scalars fo fal Scalar Update hone J i Source none v DPM Time Step none v Figure 6 4 2 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the UDF tab in the Discrete Phase Model dialog box Select the function name e g particle_body_force libudf from the Body Force drop down list under User Defined Functions Figure 6 4 2 and click OK See Section 2 5 2 DEFINE DPM BODY FORCE for details about DEFINE_DPM_BODY_FORCE functions 6 65 Release 12 0 ANSYS Inc January 26 2009 Hooking UDFs to ANSYS FLUENT 6 4 3 Hooking DEFINE_DPM_DRAG UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_DRAG UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model dialog box Figure 6 4 3 in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box eee beeen Edit Discrete Phase Model Interaction Particle Treatment C Interaction with C
52. Object Files From Non ANSYS FLUENT Sources This option is not available using the GUI After the shared library is built using the TUI or GUI you will need to load the UDF library into ANSYS FLUENT before you can use it This can be done using the Load button in the Compiled UDFs dialog box After being loaded all of the compiled UDFs that are contained within the shared library will become visible and selectable in graphics dialog boxes in ANSYS FLUENT Note that compiled UDFs are displayed in ANSYS FLUENT dialog boxes with the associated UDF library name separated by two colons For example a compiled UDF named rrate that is associated with a shared library named libudf would appear in ANSYS FLUENT dialog boxes as rrate libudf This distinguishes UDFs that are compiled from those that are interpreted If you write your case file when a UDF library is loaded the library will be saved with the case and will be automatically loaded whenever that case file is subsequently read This process of dynamic loading saves you having to reload the compiled library every time you want to run a simulation Release 12 0 ANSYS Inc January 26 2009 5 1 Introduction Before you compile your UDF source file s using one of the two methods provided in Sections 5 2 and 5 3 you will first need to make sure that the udf h header file is acces sible in your path or is saved locally within your working folder Section 5 1 1 Location of
53. Phase Interaction drag coefficient DEFINE_EXCHANGE_PROPERTY Phase Interaction lift coefficient DEFINE_EXCHANGE_PROPERTY Phase Interaction heterogeneous DEFINE_HET_RXN_RATE Phase Interaction reaction rate 2 136 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros 2 4 1 DEFINE CAVITATION RATE Description You can use DEFINE CAVITATION RATE to model the cavitation source terms Re and Re in the vapor mass fraction transport equation used in the Singhal et al model see Equation 16 7 24 in the separate Theory Guide Assuming Maot denotes the mass transfer rate between liquid and vapor phases we have Re MAX Maot oj ft Re MAX Maot 0 fo where f and f are the mass fraction of the liquid and vapor phase respectively DEFINE CAVITATION RATE is used to calculate Maot only The values of Re and Re are computed by the solver accordingly Usage DEFINE_CAVITATION_RATE name c t p rhoV rhoL mafV p_v cigma f_gas m_dot Argument Type Description symbol name UDF name cell_t c Cell index Thread t Pointer to the mixture level thread real p c Pointer to shared pressure real rhoVIc Pointer to vapor density real rhoL c Pointer to liquid density real mafVic Pointer to vapor mass fraction real p_v Pointer to vaporization pressure real cigma Pointer to liquid surface tension coefficient real f_gas Pointer to the prescribed mass fraction of non condensable gases
54. Print_Thread_Face_Centroids domain 4 fclose fout Note that Get_Domain 1 replaces the extern Domain domain expression used in pre vious releases of FLUENT 6 Release 12 0 ANSYS Inc January 26 2009 3 33 Additional Macros for Writing UDFs Set Boundary Condition Value F_PROFILE F_PROFILE is typically used in a DEFINE_PROFILE UDF to set a boundary condition value in memory for a given face and thread The index i that is an argument to F_PROFILE is also an argument to DEFINE_PROFILE and identifies the particular boundary variable e g pressure temperature velocity that is to be set F PROFILE is defined in mem h Macro F_PROFILE f t i Argument types face_t f Thread t int i Function returns void The arguments of F_PROFILE are f the index of the face face_t t a pointer to the face s thread t and i an integer index to the particular face variable that is to be set i is defined by ANSYS FLUENT when you hook a DEFINE_PROFILE UDF to a particular variable e g pressure temperature velocity in a boundary condition dialog box This index is passed to your UDF by the ANSYS FLUENT solver so that the function knows which variable to operate on Suppose you want to define a custom inlet boundary pressure profile for your ANSYS FLUENT case defined by the following equation 2 1 1x 10 0 1 x 10 y p y i x 0 0745 You can set the pressure profile using a DEFINE PROFILE UDF Since a prof
55. See Section 7 2 4 Fixing the Values of Variables in the separate User s Guide for more information on fixing variables DOC CCR 2k 2k 2K 2K I 2K k K K K A 2K 2K 2K 2K 2K 2K RK 2K K K K FK A 2K 2K 2K 2K 2K K K A kk 2K 2k ok 2 2k 2K K 2K K K 2k kk K K K K Concatenated UDFs for simulating an impeller using fixed velocity EEEE I I ooo 2 4 24 24 21 21 21 kkk k kkk kkk 2k 2k 2k include udf h define FLUID_ID 1 define ual 7 1357e 2 define ua2 54 304 define ua3 3 1345e3 define ua4 4 5578e4 define ua5 1 9664e5 define vail 3 1131e 2 define va2 10 313 define va3 9 5558e2 define va4 2 0051 e4 define vab 1 1856e5 define kal 2 2723e 2 define ka2 6 7989 define ka3 424 18 define ka4 9 4615e3 define kab 7 7251 e4 define ka6 1 8410e5 define dai 6 5819e 2 define da2 88 845 define da3 5 3731e3 define da4 1 1643e5 define dab 9 1202e5 define da6 1 9567e6 Release 12 0 ANSYS Inc January 26 2009 2 79 DEFINE Macros DEFINE_PROFILE fixed_u t i cell_t c real x ND_ND real r begin_c_loop c t centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1 F_PROFILE c t i ual ua2 r ua3 r r ua4 xr r r ua5 r r r r end_c_loop c t DEFINE_PROFILE fixed_v t i cell_t c real x ND_ND real r begin_c_loop c t lt centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1
56. The process which occurs at runtime involves a visit to the Interpreted UDFs dialog box where you Interpret a source file Inside ANSYS FLUENT the source code is compiled into an intermediate architecture independent machine code using a C preprocessor This machine code then executes on an internal emulator or interpreter when the UDF is invoked This extra layer of code incurs a performance penalty but allows an interpreted UDF to be shared effortlessly between different architectures operating systems and ANSYS FLUENT versions If execution speed does become an issue an interpreted UDF can always be run in compiled mode without modification Release 12 0 ANSYS Inc January 26 2009 1 5 Interpreting and Compiling UDFs The interpreter that is used for interpreted UDFs does not have all of the capabilities of a standard C compiler which is used for compiled UDFs Specifically interpreted UDFs cannot contain any of the following C programming language elements 1 5 1 goto statements non ANSI C prototypes for syntax direct data structure references declarations of local structures unions pointers to functions arrays of functions multi dimensional arrays Differences Between Interpreted and Compiled UDFs The major difference between interpreted and compiled UDFs is that interpreted UDFs cannot access ANSYS FLUENT solver data using direct structure references they can only indirectly access data through the use
57. The second function writer instructs ANSYS FLUENT to write the current value of kount to the data file when the data file is saved The third function reader instructs ANSYS FLUENT to read the value of kount from the data file when the data file is read The functions work together as follows If you run your calculation for say 10 iterations kount has been incremented to a value of 10 and save the data file then the current value of kount 10 will be written to your data file If you read the data back into ANSYS FLUENT and continue the calculation kount will start at a value of 10 and will be incremented at each iteration Note that you can save as many static variables as you want but you must be sure to read them in the same order in which they are written Hooking a Read Write Case or Data File UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_RW_FILE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g writer will become visible and selectable via the User Defined Function Hooks dialog box in ANSYS FLUENT Note that you can hook multiple read write functions to your model See Section 6 1 7 Hook ing DEFINE_RW_FILE UDFs for details 2 24 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 Model Specific DEFINE Macros The DEFINE macros presented in t
58. Usage DEFINE_SOLAR_INTENSITY name sum_x sun_y sun_z S_hour S_minute Argument Type Description symbol name UDF name real sun_x x component of the sun direction vector real suny y component of the sun direction vector real sun z z component of the sun direction vector real S_hour Time in hours real S_minute Time in minutes Function returns real There are six arguments to DEFINE_SOLAR_INTENSITY name sun_x sun_y sun_z S_hour and S_minute You provide the name of your user defined function The variables sun_x sun_y sun_z S_hour and S_minute are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the direct or diffuse solar irradiation and return the real value in w m to the solver Example The following source code contains two UDFs sol_direct_intensity computes the di rect solar irradiation and returns it to the ANSYS FLUENT solver and sol_diffuse_intensity computes the diffuse solar irradiation 2 98 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros include udf h DEFINE_SOLAR_INTENSITY sol_direct_intensity sun_x sun_y sun_z hour minute real intensity intensity 1019 printf solar time f intensity e n minute intensity return intensity DEFINE_SOLAR_INTENSITY sol_diffuse_intensity sun_x sun_y sun_z hour minute real intensity intensity 275 printf solar time f intensity diff e n minute intensity retu
59. Usage DEFINE_SPECIFIC_HEAT name T Tref h yi Argument Type Description symbol name UDF name real T Temperature for the calculation of the specific heat and enthalpy real Tref Reference temperature for the enthalpy calculation real h Pointer to real real yi Pointer to array of mass fractions of gas phase species Function returns real There are five arguments to DEFINE_SPECIFIC_HEAT name T Tref h and yi You supply name the name of the UDF T and Tref are real variables that are passed by the ANSYS FLUENT solver to the UDF and h is a pointer to real The UDF needs to return the real value of the specific heat and set the sensible enthalpy to the value referenced by the real pointer h Note that the entropy is not computed in the UDF instead ANSYS FLUENT sets the entropy as S cp T mean log T Tref where cp is computed by the UDF at T mean and Tmean is the mean logarithmic average of T and Tref Release 12 0 ANSYS Inc January 26 2009 2 1 13 DEFINE Macros Example peaa ooo kkk kk kkk kk kkk kkk A A A kk kk kkk kk k k UDF that computes specific heat and sets the sensible enthalpy to the referenced value FER RR RK Ra kK a kk a 3k 2k a 2k 2k ak kk a ak include udf h DEFINE_SPECIFIC_HEAT my_user_cp T Tref h yi real cp 2000 h cp T Tref return cp J Hooking a Specific Heat UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SPECIFIC_HEAT is compile
60. Wu Correlation of Autoignition Phenomena in Internal Combustion Engines and Rapid Compression Machines In Fifth Symposium Int on Combustion pages 347 356 1955 M J Moran and H N Shapiro Fundamentals of Engineering Thermodynamics John Wiley amp Sons Inc 1988 S Oualline Practical C Programming O Reilly Press 1997 M R Speigel Mathematical Handbook of Formulas and Tables Shaum s Outline Series McGraw Hill Co 1968 Release 12 0 ANSYS Inc January 26 2009 Bib 1 BIBLIOGRAPHY Bib 2 Release 12 0 ANSYS Inc January 26 2009 Index A ND_ND 3 27 accessing domain pointer not passed as argument 3 31 accretion rate UDFs 2 167 Adaptive Time Step Settings dialog box 6 3 adjacent cell index macros 3 26 adjacent cell thread macros 3 27 adjust UDFs 2 4 advection term 2 231 advective flux field 2 231 anisotropic diffusivity UDFs 2 227 ANSYS FLUENT data types 1 10 solution process 1 12 variables accessing 3 1 area normal vector macro 3 27 arithmetic operators A 12 arrays A 8 ARRH 3 40 3 41 3 43 Arrhenius constants 2 115 axisymmetric considerations for macros 3 4 batch file compilation 5 4 end_c_loop 3 57 7 22 begin end_c_loop_ext 7 22 end_c_loop_int 7 22 end_floop 3 57 7 22 begin_c_loop_all 2 18 body force UDFs 2 163 boiling point UDF 2 186 boundary condition UDFs examples 8 14 for DPM 2 156 general purpose 2 72 boundary conditions 1 3 begi
61. data related to the particle being tracked Pointer to array containing mass fractions of the solid species in the particle char mass at the current time step Diffusion controlled species as defined in the Reactions dialog box for the current reaction Catalyst species as defined in the Reactions dialog box for the current reaction Pointer to array containing particle reaction rate kg s There are eleven arguments to DEFINE_PR_RATE name c t r mw ci p sf dif_index cat_index and rr You supply name the name of the UDF c t r mw ci p sf dif index cat_index and rr are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the value referenced by the real pointer rr to the particle reaction rate in kg s Note that p is an argument to many particle specific macros defined in Section 3 2 7 DPM Macros and can be used to obtain information about particle properties Also note that the order in which the solid species mass fractions are stored in array sf is the same as the order in which the species are defined in the Selected Solid Species list in the Create Edit Materials dialog box which is opened from the Edit Species names option for the Mixture Material Release 12 0 ANSYS Inc January 26 2009 2 59 DEFINE Macros DEFINE_PR_RATE is called by ANSYS FLUENT every time step during the particle tracking calculation The auxiliary function zbrent_pr_rate is used when there
62. define MWT 44 01 define PCRIT 7 3834e6 define TCRIT 304 21 define ZCRIT 0 2769 define VCRIT 2 15517e 3 define NRK 0 77 IDEAL GAS SPECIFIC HEAT CURVE FIT define CC1 453 577 define CC2 1 65014 define CC3 1 24814e 3 define CC4 3 78201e 7 define CC5 0 00 REFERENCE STATE define P_REF 101325 define T_REF 288 15 8 54 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Redlich Kwong Real Gas UDRGM Code Listing PRR OO k k kkk k kkk kkk k kkk k kkk kkk k kkk k 24 2k 2 2k 6 2k k 2k 26 2k kk User Defined Function Redlich Kwong Equation of State for Real Gas Modeling Author Frank Kelecy Date May 2003 Version 1 02 This implementation is completely general Parameters set for C02 DRO OO k k kkk OK OR k kkk k kkk kkk k kkk kkk k kkk k 2k ak 2k k k include udf h include stdio h include ctype h include stdarg h The variables below need to be set for a particular gas C02 REAL GAS EQUATION OF STATE MODEL BASIC VARIABLES ALL VARIABLES ARE IN SI UNITS define RGASU UNIVERSAL_GAS_CONSTANT define PI 3 141592654 define MWT 44 01 define PCRIT 7 3834e6 define TCRIT 304 21 define ZCRIT 0 2769 define VCRIT 2 15517e 3 define NRK 0 77 Release 12 0 ANSYS Inc January 26 2009 8 55 Examples IDEAL GAS SPECIFIC HEAT CURVE
63. density MIXTURE_mw yi i cv yili RKEOS_vol_specific_heat temp mw i density MIXTURE_mw yi i return sqrt cp cv dvdp v FUNCTION MIXTURE_rho_t double MIXTURE_rho_t double temp double density double P double yil double rho_t 0 int i for i 0 i lt n_specs i if yili gt SMLL rho_t yili density density RKEOS_dvdt temp Release 12 0 ANSYS Inc January 26 2009 8 83 Examples mw i density MIXTURE_mw yi i return rho_t FUNCTION MIXTURE_rho_p 5 double MIXTURE_rho_p double temp double density double P double yi double rho_p 0 int i for i 0 i lt n_specs i if yilil gt SMLL rho_p yili density density RKEOS_dvdp temp mw i density MIXTURE_mw yi i return rho_p FUNCTION MIXTURE_enthalpy_t double MIXTURE_enthalpy_t double temp double density double P double yil return MIXTURE_specific_heat temp density P yi FUNCTION MIXTURE_enthalpy_p double MIXTURE_enthalpy_p double temp double density doubl
64. double MIXTURE_speed_of_sound double Temp double density double P double yi t double a cp Rgas MIXTURE_specific_heat Temp density P yi Mixture_Rgas yi cp Rgas sqrt Rgas Temp cp cp Rgas w Il return a m s double MIXTURE_viscosity double Temp double density double P double yil double mu 0 int i for i 0 i lt n_specs i mu yi i xMu_i Temp density i return mu Kg m s ty double MIXTURE_thermal_conductivity double Temp double density double P 8 70 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double yil double kt 0 int i for i 0 i lt n_specs i kt yili K_i Temp density i return kt W m K double MIXTURE_rho_t double Temp double density double P double yil double drdT derivative of rho w r t Temp double p double dT 0 01 p Mixture_pressure Temp density yi drdT MIXTURE_density Temp dT p yi MIXTURE_density Temp p yi dT return drdT Kg m 3 K double MIXTURE_rho_p double Temp double density double P double yi double drdp double p double dp 5 0 p Mixture_pressure Temp density yi drdp MIXTURE_density Temp p dp yi MIXTURE_density Temp p yi dp return drdp Kg m 3 Pa double MIXTURE_enthalpy_t double Temp double density double P double yi double dhdT double p double rho2 double dT 0 01
65. dt pres temp yk void name int cell_t c Thread t Particle p int num_p int n_spe double dt double pres double temp double yk define DEFINE_CPHI name c t real name cell_t c Thread t define DEFINE_DIFFUSIVITY name c t i real name cell_t c Thread t int i define DEFINE_DOM_DIFFUSE_REFLECTIVITY name t nb n_a n_b diff_ ref_a diff_tran_a diff_ref_b diff_tran_b void name Thread t int nb real n_a real n_b real diff_ref_a real diff_tran_a real diff_ref_b real diff_tran_b define DEFINE_DOM_SPECULAR_REFLECTIVITY name f t nb n_a n_b ray_direction e_n total_internal_reflection specular_reflectivity specular_transmissivity void name face_t f Thread t int nb real n_a real n_b real ray_direction real e_n int total_internal_reflection real specular_reflectivity real specular_transmissivity define DEFINE_DOM_SOURCE name c t ni nb emission in_scattering abs_coeff scat_coeff void name cell_t c Thread t int ni int nb real emission real in_scattering real abs_coeff real scat_coeff define DEFINE_EMISSIVITY_WEIGHTING_FACTOR name c t T nb emissivity_weighting factor void name cell_t c Thread t real T int nb real emissivity_weighting factor define DEFINE_GRAY_BAND_ABS_COEFF mame c t nb real name cell_t c Thread t int nb define DEFINE_HEAT_FLUX name f t c0 tO cid cir void name fa
66. it could be a vendor implementation of the Message Passing Interface MPI standard as depicted in Figure 7 1 4 All of the parallel ANSYS FLUENT processes as well as the serial process are identified by a unique integer ID The host process is assigned the ID node_host 999999 The host collects messages from compute node 0 and performs operation such as printing displaying messages and writing to a file on all of the data in the same way as the serial solver Figure 7 1 5 Release 12 0 ANSYS Inc January 26 2009 7 1 Overview of Parallel ANSYS FLUENT HOST COMPUTE NODES 2 i Figure 7 1 4 Parallel ANSYS FLUENT Architecture Release 12 0 ANSYS Inc January 26 2009 7 5 Parallel Considerations Print messages Figure 7 1 5 Example of Command Transfer in Parallel ANSYS FLUENT 7 6 Release 12 0 ANSYS Inc January 26 2009 7 2 Cells and Faces in a Partitioned Mesh 7 2 Cells and Faces in a Partitioned Mesh Some terminology needs to be introduced to distinguish between different types of cells and faces in a partitioned mesh Note that this nomenclature applies only to parallel coding in ANSYS FLUENT Cell Types in a Partitioned Mesh There are two types of cells in a partitioned mesh interior cells and exterior cells Fig ure 7 2 1 Interior cells are fully contained within a mesh partition Exterior cells on one compute node correspond to the same interior cells in the ad
67. only See the example below for details Release 12 0 ANSYS Inc January 26 2009 2 87 DEFINE Macros For Multiphase Flows e surface tension coefficient VOF model e cavitation parameters including surface tension coefficient and vaporization pres sure Mixture cavitation models e heat transfer coefficient Mixture model e particle or droplet diameter Mixture model e speed of sound function Mixture cavitation models e density as a function of pressure for compressible liquid flows only Mixture cavitation models e granular temperature and viscosity Mixture Eulerian models e granular bulk viscosity Eulerian model e granular conductivity Eulerian model e frictional pressure and viscosity Eulerian model e frictional modulus Eulerian model e elasticity modulus Eulerian model e radial distribution Eulerian model e solids pressure Eulerian Mixture models e diameter Eulerian Mixture models Usage DEFINE_PROPERTY name c t Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the property function is to be applied Function returns real 2 88 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros There are three arguments to DEFINE_PROPERTY name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will nee
68. open_udf_library No such file or directory Windows Parallel If you are trying to load a compiled UDF while running ANSYS FLUENT in network parallel you may receive this error Error open_udf_library The system cannot find the path specified Release 12 0 ANSYS Inc January 26 2009 5 27 Compiling UDFs This error occurs because the other computer s on the cluster cannot see the UDF through the network To remedy this you will need to 1 modify the environment variables on the computer where the compiled UDF case and data files reside and 2 share the folder where the files reside See Section 5 2 Compiling a UDF Using the GUI for details on file sharing or contact ANSYS FLUENT installation support for additional assistance There are instances when ANSYS FLUENT can hang when trying to read a compiled UDF using network parallel as a result of a network communicator problem Contact ANSYS FLUENT installation support for details You may receive an error message when you invoke the command nmake if you have the wrong compiler installed or if you have not launched the Visual Studio Command Prompt prior to building the UDF See Section 5 1 2 Compilers and Section 5 2 Compiling a UDF Using the GUI for details or contact ANSYS FLUENT installation support for further assistance 5 7 Special Considerations for Parallel ANSYS FLUENT If you are running serial or parallel ANSYS FLUENT on a Windows system and intend to co
69. pow sqrt dd fabs rr 0 333333 vv tt qq tt a1 3 else if rr sqrt qq3 lt 1 tt PI else if rr sqrt qq3 gt 1 tt 0 else tt acos rr sqrt qq3 sqq sqrt qq vvi 2 sqq cos tt 3 a1 3 vv2 2 sqq cos tt 2 PI 3 a1 3 vv3 2 sqq cos tt 4 PI 3 a1 3 8 88 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples VV vvi gt vv2 vvl vv2 VV vv gt vv3 vv vv3 MessageO Three roots f f f n vv1 vv2 vv3 return vv FUNCTION RKEOS_dvdp Returns dv dp given T and rho double RKEOS_dvdp double temp double density int i double afun a0 i pow tcrit i temp nrk i double dterm dterm2 double v 1 density dterm1 rgas i temp pow v b0 i cO i 2 0 dterm2 afun 2 0 v b0 i pow v v b0 i 2 0 return 1 dtermi dterm2 FUNCTION RKEOS_dvdt Returns dv dT given T and rho double RKEOS_dvdt double temp double density int i double dpdT dterm1 dterm2 double afun a0 i pow tcrit i temp nrk i double v 1 density dtermt rgas i v b0 i cO i dterm2 nrk i afun v v b0 i temp dpdT dtermit dterm 2 return RKEOS_dvdp temp density i d
70. real m_dot Pointer to cavitation mass transfer rate Function returns void There are eleven arguments to DEFINE_CAVITATION_RATE name c t p rhoV rhoL mafV p_v cigma f_gas and m_dot You supply name the name of the UDF c t p rhoV rhoL mafV p_v cigma f_gas and m_dot are variables that are passed by the ANSYS Release 12 0 ANSYS Inc January 26 2009 2 1 37 DEFINE Macros FLUENT solver to your UDF Your UDF will need to set the value referenced by the real pointer m_dot to the cavitation rate Example The following UDF named c_rate is an example of a cavitation model for a multiphase mixture that is different from the default model in ANSYS FLUENT This cavitation model calculates the cavitation mass transfer rates between the liquid and vapor phase depending on fluid pressure p turbulence kinetic energy C_K c t and the liquid vaporization pressure p_v In general the existence of turbulence enhances cavitation In this example the tur bulence effect is taken into account by increasing the cavitation pressure by 0 195 CR c t CK c t The pressure p_vapor that determines whether cavitation occurs increases from p_v to p_v 0 195 C_R c t C_K c t When the absolute fluid pressure ABS_P is lower than p_vapor then liquid evaporates to vapor Re When it is greater than p_vapor vapor condenses to liquid Re The evaporation rate is calculated by If ABS_P lt p_vapor then c_ev
71. 00 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros There are five arguments to DEFINE_SOURCE name c t dS and eqn You supply name the name of the UDF c t dS and eqn are variables that are passed by the ANSYS FLUENT solver to your UDF Note that the source term derivatives may be used to linearize the source term if they enhance the stability of the solver To illustrate this note that the source term can be expressed in general as Equation 2 3 9 where is the dependent variable A is the explicit part of the source term and B is the implicit part I A Bd 2 3 9 Specifying a value for B in Equation 2 3 9 can enhance the stability of the solution and help convergence rates due to the increase in diagonal terms on the solution matrix ANSYS FLUENT automatically determines if the value of B that is given by the user will aid stability If it does then ANSYS FLUENT will define A as S 0S 0 and B as OS 0 If not the source term is handled explicitly Your UDF will need to compute the real source term only for a single cell and return the value to the solver but you have the choice of setting the implicit term dS eqn to dS d or forcing the explicit solution of the source term by setting it equal to 0 0 Note that like property UDFs source term UDFs defined using DEFINE_SOURCE are called by ANSYS FLUENT from within a loop on cell threads The solver passes to the DEFINE_
72. 1 0 x 1 2 diff 2 x 2 0 x 2 2 dmatrix 2 0 dmatrix 0 2 dmatrix 1 2 diff 0 x 0 1 x 0 2 diff 1 x 1 1 x 1 2 diff 2 x 2 1 x 2 2 Jose torial dmatrix 1 2 endif Release 12 0 ANSYS Inc January 26 2009 2 229 DEFINE Macros Hooking an Anisotropic Diffusivity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_ANISOTROPIC_DIFFUSIVITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g cyl_ortho diff will become selectable via the UDS Diffusion Coefficients dialog box You ll first need to select defined per uds for UDS Diffusivity in the Create Edit Materials dialog box then select the user defined anisotropic option for Coefficient from the UDS Diffusion Coefficients dialog box for a particular user defined scalar diffusion equa tion e g uds 0 See Section 6 6 1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs for details 2 7 3 DEFINE UDS FLUX Description You can use DEFINE_UDS_FLUX to customize how the advective flux term is computed in your user defined scalar UDS transport equations See Section 9 1 User Defined Scalar UDS Transport Equations in the separate User s Guide for details on setting up and solving UDS transport equations Usage DEFINE_UDS_FLUX name f t i Argument Type Description sym
73. 1 02 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 2 Degassing Boundary Condition The following UDFs are used to define the bottom surface as a standard velocity inlet for the gas primary phase The inlet VOF of the droplet phase is 0 and a negative source term for secondary phase mass conservation is set for the layer of cells next to the outlet The source removes all secondary phase mass in the cell during one time step The recoil force due to the mass source is also calculated DCCC OO OO k kkk IO a a a kkk k kkk kkk This UDF is an implementation of the degassing boundary condition PRR oo oo o kk k kkk kkk k kkk include include include include include include udf h sg h sg_mphase h flow h mem h metric h DEFINE_SOURCE degassing_source cell thread dS eqn real source Thread tm THREAD_SUPER_THREAD thread source C_R cell thread C_VOF cell thread CURRENT_TIMESTEP C_UDMI cell tm 0 source dS eqn C_R cell thread CURRENT_TIMESTEP return source DEFINE_SOURCE x_prim_recoil cell tp dS eqn real source Thread tm THREAD_SUPER_THREAD tp Thread ts ts THREAD_SUB_THREAD tm 1 source ds eqn C_R cell ts C_VOF cell ts CURRENT_TIMESTEP C_U cell tp C_R cell ts C_VOF cell ts CURRENT_TIMESTEP Release 12 0 ANSYS Inc January 26 2009 2 1 03 DEFINE Macros
74. 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros DOO AAAS ARIAS ARICA IK Ka UDF that implements a simplified advective term in the scalar transport equation DEBORA CAAA AAO OA AAO OOOO SSRIS ARIAS A Ka include udf h DEFINE_UDS_FLUX my_uds_flux f t i cell_t c0 cl 1 Thread t0 t1 NULL real NV_VEC psi_vec NV_VEC A flux 0 0 c0 F_CO f t tO F_CO_THREAD f t F_AREA A f t If face lies at domain boundary use face values If face lies IN the domain use average of adjacent cells if BOUNDARY_FACE_THREAD_P t Most face values will be availablex real dens Depending on its BC density may not be set on face thread if NNULLP THREAD_STORAGE t SV_DENSITY dens F_R f t Set dens to face value if available else dens C_R c0 t0 else set dens to cell value NV_DS psi_vec F_U f t F_V f t F_W f t dens flux NV_DOT psi_vec A flux through Face else c1 F_C1 f t Get cell on other side of face ti F_C1_THREAD f t NV_DS psi_vec C_U c0 t0 C_V c0 t0 C_W cO t0 C_R c0 t0 NV_DS psi_vec C_U c1 t1 C_V c1 t1 C_W c1 t1 C_R c1 t1 Release 12 0 ANSYS Inc January 26 2009 2 233 DEFINE Macros flux NV_DOT psi_vec A 2 0 Average flux through face ANSYS FLUENT will multiply the returned value by phi_f the scalar s value at the face
75. 37 P_RHO 2 159 2 177 2 182 3 36 P_RHOO 3 37 P_T 2 197 3 36 P_T0 3 37 P_TIME 2 164 3 36 P_TIMEO 3 37 P_USER_REAL 2 168 3 37 P_VEL 2 159 2 164 3 36 P_VELO 2 159 3 37 P_VFF 3 36 parabolic velocity UDF example 8 14 PARALLEL 7 13 7 40 parallel macros 7 12 global logicals 7 21 global maximums and minimums 7 20 global sums 7 20 global synchronization 7 22 parallel UDF example 7 37 parallel UDFs about 7 1 communication macros 7 15 global reduction macros 7 18 macros 7 12 Release 12 0 ANSYS Inc January 26 2009 Index overview 7 1 predicates 7 17 writing files 7 40 parallelizing your serial UDF 7 12 partially premixed unburnt density 2 87 unburnt specific heat 2 87 unburnt temperature 2 87 unburnt thermal diffusivity 2 87 particle boundary condition UDF 2 156 custom law UDFs 2 181 diameter 2 177 drag coefficient 2 165 emissivity UDF 2 186 equilibrium vapor pressure UDF 2 205 erosion and accretion rate 2 167 injection initialization 2 177 law UDFs for DPM 2 181 location 2 177 material property UDFs 2 186 reaction rate UDFs 2 58 sampling output UDF 2 183 scalar update UDFs 2 189 scattering factor UDF 2 186 source term UDF s 2 193 source terms 2 193 spray collide UDFs 2 194 surface tension UDF 2 186 switching law UDFs 2 196 time step control UDF 2 202 velocity 2 177 viscosity UDF 2 186 particle or droplet diameter 2 88 partitioned mesh terms 7 7 par
76. 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g heat_udf will become visible and selectable in the Phase Interaction dialog box in ANSYS FLUENT See Section 6 3 2 Hooking DEFINE_EXCHANGE_PROPERTY UDFs for details 2 4 3 DEFINE_HET_RXN_RATE Description You need to use DEFINE_HET_RXN_RATE to specify reaction rates for heterogeneous reac tions A heterogeneous reaction is one that involves reactants and products from more than one phase Unlike DEFINE_VR_RATE a DEFINE HET RXN_RATE UDF can be specified differently for different heterogeneous reactions During ANSYS FLUENT execution the DEFINE_HET_RXN_RATE UDF for each heteroge neous reaction that is defined is called in every fluid cell ANSYS FLUENT will use the reaction rate specified by the UDF to compute production destruction of the species participating in the reaction as well as heat and momentum transfer across phases due to the reaction A heterogeneous reaction is typically used to define reactions involving species of differ ent phases The bulk phase can participate in the reaction if the phase does not have any species i e phase has fluid material instead of mixture material Heterogeneous reactions are defined in the Phase Interaction dialog box 2 1 44 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros Usage DEFINE HET RXN_RATE name c t r mw yi rr rr_t Argument Type Description
77. 6 1 1 The User Defined Function Hooks Dialog Box Click the Edit button next to Adjust to open the Adjust Functions dialog box Fig ure 6 1 2 6 2 Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking General Purpose UDFs Adjust Functions Available Adjust Functions E B Selected Adjust Functions E 6B adjust _fen2 libudf adjust _fen libudf Figure 6 1 2 The Adjust Functions Dialog Box Select the function s you wish to hook to your model from the Available Adjust Functions list Click Add and then OK to close the dialog box The name of the function you selected will be displayed in the Adjust field of the User Defined Function Hooks dialog box If you select more than one function the number will be displayed e g 2 selected Click OK in the User Defined Function Hooks dialog box to apply the settings See Section 2 2 1 DEFINE ADJUST for details about defining adjust functions using the DEFINE_ADJUST macro 6 1 2 Hooking DEFINE_DELTAT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DELTAT UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Adaptive Time Step Settings dialog box Figure 6 1 3 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT select Transient from the Time list in the Solver group box of the General task page gt Kee Transient Then open
78. 67 6 4 5 Hooking DEFINE DPM_HEAT MASS UDFs 6 68 6 4 6 Hooking DEFINE_DPM_INJECTION_INIT UDFs 6 69 6 4 7 Hooking DEFINE_DPMLAWUDFs 2 4 6 71 64 8 Hooking DEFINE DPM OUTPUT UDFs 444 444454 46 4 6 72 6 4 9 Hooking DEFINE DPM_PROPERTY UDFs 6 73 6 4 10 Hooking DEFINE DPM_SCALAR_UPDATE UDFs 6 75 6 4 11 Hooking DEFINE DPM_SOURCE UDFs 6 76 6 4 12 Hooking DEFINE DPM_SPRAY_COLLIDE UDFs 6 77 64 13 Hooking DEFINE DPM SWITCH UDFS lt lt 246 ee dae ee as 6 78 6 4 14 Hooking DEFINE DPM_TIMESTEP UDFs 6 79 6 4 15 Hooking DEFINE_DPM_VP_EQUILIB UDFs 6 80 Go Hooking Dynamic Mesh UDFS 2 24 a sd sis amp seek Se sce ye ate amp 6 81 6 5 1 Hooking DEFINE CGMOTION UDES gt lt S nisa d r 2 2a 4 6 81 6 5 2 Hooking DEFINE_DYNAMIC_ZONE_PROPERTY UDFs 6 82 6 5 3 Hooking DEFINE GEOM UDPS oo 24 22 be ee eb a Xe ns 6 85 6 5 4 Hooking DEFINE_GRID_MOTION UDFs 6 87 6 5 5 Hooking DEFINE_SDOF_PROPERTIES UDFs 6 88 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs 6 90 6 6 1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs 6 90 60 2 Hooking DEFINE UDS FLUX UDES e acc e s 4 4 a e amp ee we Gee 6 93 6 6 3 Hooking DEFINEUDS_UNSTEADY UDFs 6 94 6 7 Common Errors While Hooking a UDF to ANSYS FLUENT 6 95 Parallel Considerations 7 1 7 1 Overview of Parallel AN
79. 8 C_PHASE_DIAMETER 2 143 CR B35 D117 2196 9190 Dia aa 2 150 2 152 2 232 3 8 C RMI 2 235 C STORAGE R 2 235 CT 290 292 2117 2 150 2 197 3 8 8 31 Index 2 Cli atii 841g oe C_UDMI 2 20 2 168 3 49 6 13 C_UDSI 2 6 3 45 CV 2 141 2 143 3 8 C VOF 2 141 2 143 2 150 3 60 C_VOLUME 2 5 2 9 2 20 2 235 3 6 CW 2 148 3 8 C_YI 2 92 2 177 3 8 case file functions reading and writing 2 23 casting A 7 cavitation rate UDF 2 137 cell 1 10 accessing neighboring thread variables 1 8 values checking accessibility 3 80 cell centroid 3 25 cell centroid macro 3 6 cell face 1 9 cell face index macro 3 7 cell face macros 3 7 cell face thread macro 3 7 cell gradient macros 3 9 cell ID 1 11 cell identifier 3 2 cell looping macro general purpose 7 24 cell looping macros parallel 7 22 cell partition IDs parallel 7 27 cell reconstruction gradient macros 3 15 cell variables macros 3 6 cell volume macro 3 6 cell zone 1 9 cell_t data structure 1 10 center of gravity motion UDF 2 209 chemistry step UDFs 2 31 coal emissivity 2 187 coal scattering 2 187 communication macros parallel 7 15 7 16 Compiled UDFs dialog box 5 2 5 6 8 9 8 10 Release 12 0 ANSYS Inc January 26 2009 Index compiled UDFs 1 2 1 6 building shared library 5 2 environment 5 4 example 8 38 8 43 GUI 5 5 restrictions 1 7 shared library 1 6 Windows parallel network 5 5 5 28 writing case fi
80. 8 25 step by step 8 1 file inclusion directive 1 1 for multiphase applications 1 17 for UDS transport equations 2 225 header file 1 5 include statement 1 5 interpreted 1 6 interpreted versus compiled 1 6 interpreting 4 3 limitations 1 3 programming language 1 1 purpose 1 3 single phase vs multiphase 1 17 Release 12 0 ANSYS Inc January 26 2009 Index source files compiled 1 6 interpreted 1 6 tutorial 8 1 UDRGM see user defined real gas model UDRGM DS diffusivity UDFs 2 34 JDS flux UDFs 2 230 DS source term UDFs 2 226 DS transport equation UDFs 2 225 DS transport equations 1 3 diffusivity UDFs 2 34 JDS UDFs anisotropic diffusivity 2 227 diffusion coefficient 2 225 examples 8 40 flux 2 226 2 230 postprocessing example 8 40 source terms 2 226 unsteady 2 226 unsteady term 2 234 UNIVERSAL_GAS_CONSTANT 2 60 2 61 3115 2117 9 190 9 62 UNIX systems directory structure 5 12 shared library 5 16 unstable simulations 3 16 unsteady term UDFs 2 234 unsteady UDFs 2 226 Use Contributed CPP 4 4 8 7 user defined data types A 7 User Defined Function Hooks dialog box 6 2 6 5 6 6 6 9 6 11 6 14 6 15 6 19 6 22 6 24 6 30 6 47 6 48 6 50 6 53 6 56 User Defined Functions dialog box 6 37 6 39 6 42 6 58 6 62 6 74 user defined functions see UDFs User Defined Memory dialog box 6 13 user defined memory 2 20 2 168 6 13 state ad g Release 12 0 ANSYS
81. 9 i DEFINE_EXECUTE_ON_LOADING UDFs can be executed only as compiled UDFs Usage DEF INE_EXECUTE_ON_LOADING name 1libname Argument Type Description symbol name UDF name char libname compiled UDF library name Function returns void There are two arguments to DEFINE_EXECUTE_ON_LOADING name and libname You sup ply a name for the UDF which will be used by ANSYS FLUENT when reporting that the EXECUTE_ON_LOADING UDF is being run The libname is set by ANSYS FLUENT to be the name of the library e g libudf that you have specified by entering a name or Release 12 0 ANSYS Inc January 26 2009 2 13 DEFINE Macros keeping the default libudf libname is passed so that you can use it in messages within your UDF Example 1 The following simple UDF named report_version prints a message on the console that contains the version and release number of the library being loaded include udf h static int version 1 static int release 2 DEF INE_EXECUTE_ON_LOADING report_version libname Message nLoading 4s version 7 d d n libname version release Example 2 The following source code contains two UDFs The first UDF is an EXECUTE_ON_LOADING function that is used to reserve three UDMs using Reserve User Memory Vars for a library and set unique names for the UDM locations using Set_User Memory_Name The second UDF is an ON_DEMAND function that is used to set the values of the UDM locations after t
82. C INTEGER SIZE COMMON SIZE ARRAY 10 COMMON TSTCOM ICOM XCOM YCOM ZCOM ICOM C XCOM A YCOM B ZCOM CMPLX A REAL B SIZE 10 DO 100 I 1 SIZE ARRAY 1 I A 100 CONTINUE ADDAB A C B END COMPLEX FUNCTION CCMPLX A B REAL A B Release 12 0 ANSYS Inc January 26 2009 5 21 Compiling UDFs 5 22 CCMPLX CMPLX A B END 2 The UDF C source file named test_use c is placed in the source folder for the ultra 2d version src ultra 2d The source listing for test_use c is as follows include udf h if defined _WIN32 Visual Fortran makes uppercase functions provide lowercase mapping to be compatible with UNIX code define addab_ ADDAB endif typedef struct float r i Complex typedef struct double r i DComplex typedef struct long double r i QComplex FORTRAN QUAD PRECISION FORTRAN FUNCTION extern double addab_ float a double b int c NOTE on SUN machines that FORTRAN functions returning a complex number are actually implemented as void but with an extra initial argument extern void ccmplx_ Complex z float a float b extern void qcmplx_ QComplex z float a float b BLANK COMMON BLOCK extern struct int size float array 10 _BLNK__ Release 12 0 ANSYS Inc January 26 2009 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources FORTRAN NAMED COMMON BLOCK extern struct int int_c float
83. C types functions and preprocessor macros to fa cilitate the programming of UDFs and the use of CFD objects as defined inside ANSYS FLUENT The previous chapter presented DEFINE macros with which you must define your UDF This chapter presents predefined functions implemented as macros in the code that are supplied by ANSYS FLUENT that you will use to code your UDF These macros allow you to access data in an ANSYS FLUENT solver such as cell variables e g cell temperature centroid face variables e g face temperature area or connectivity variables e g adjacent cell thread and index that your UDF can use in a computation A special set of macros commonly used in UDFs is provided that return such values as the thread ID pointer an internal ANSYS FLUENT structure when passed the Zone ID the number assigned to a zone in a boundary conditions dialog box Another special macro F_PROFILE enables your UDF to set a boundary condition value in the solver Other types of macros are provided that enable your function to loop over nodes cells and faces in a thread or domain in order to retrieve and or set values Finally data access macros that are specific to a particular model e g DPM NO are presented as well as macros that perform vector time dependent Scheme and I O operations Release 12 0 ANSYS Inc January 26 2009 3 1 Additional Macros for Writing UDFs Function definitions for the macros provided in this chapte
84. Errors When Building and Loading a UDF Library If your compiled UDF library loads successfully then each function contained within the library will be reported to the console and log file For example if you built a shared library named libudf containing two user defined functions superfluid_density and speed_sound a successful library load on a Linux machine will result in the following message reported to the console and log file for a Linux machine Opening library libudf Library libudf 1nx86 3d libudf so opened superfluid_density speed_sound Done If instead no function names are listed then it is likely that your source file did not successfully compile In this case you ll need to consult the log to view the compilation history and debug your function s Note that you ll need to unload the UDF library using the UDF Library Manager dialog box before you reload the debugged version of your library Another common error occurs when you try to read a case file that was saved with a shared library and that shared library has subsequently been moved to another location In this case the following error will be reported to the console and log file on a Linux machine Opening library libudf Error open_udf_library couldn t open library libudf 1n86 2d libudf so Similarly you will get an error message when you try to load a shared library before it has been built Opening library libudf Error
85. Examples FUNCTION RKEOS_speed_of_sound Returns s o s given T and rho double RKEOS_speed_of_sound double temp double density double P double yi double cp RKEOS_specific_heat temp density P yi double dvdt RKEOS_dvdt temp density double dvdp RKEOS_dvdp temp density double v 1 density double delta_c temp dvdt dvdt dvdp return sqrt cp delta_c cp dvdp v m s FUNCTION RKEOS_rho_t double RKEOS_rho_t double temp double density double P double yil return density density RKEOS_dvdt temp density FUNCTION RKEOS_rho_p double RKEOS_rho_p double temp double density double P double yi return density density RKEOS_dvdp temp density FUNCTION RKEOS_enthalpy_t double RKEOS_enthalpy_t double temp double density double P double yi return RKEOS_specific_heat temp density P yi Release 12 0 ANSYS Inc January 26 2009 8 63 Examples FUNCTION RKEOS_enthalpy_p
86. FLUENT does not currently provide the capability to unreserve UDM variables using a macro Unreserve macros will be available in future versions of ANSYS FLUENT You will need to exit ANSYS FLUENT to ensure that all UDM variables are reset Release 12 0 ANSYS Inc January 26 2009 3 55 Additional Macros for Writing UDFs 3 3 Looping Macros Many UDF tasks require repeated operations to be performed on nodes cells and threads in a computational domain For your convenience ANSYS FLUENT has provided you with a set of predefined macros to accomplish looping tasks For example to define a custom boundary profile function you will need to loop over all the faces in a face thread using begin end_f_loop looping macros For operations where you want to loop over all the faces or cells in a domain you will need to nest a begin end_f_loop or begin end_c_loop inside a thread_loop_f or thread_loop_c respectively The following general looping macros can be used for UDFs in single phase or multiphase models in ANSYS FLUENT Definitions for these macros are contained in the mem h header file i You should not access a scheme variable using any of the RP_GET_ func tions from inside a cell or face looping macro c_loop or f loop This type of communication between the solver and cortex is very time consuming and therefore should be done outside of loops Looping Over Cell Threads in a Domain thread_loop_c You can use thread_loop_
87. F_PROFILE c t i val va2 r va3 r r va4 r r r va5 r r r r end_c_loop c t DEFINE_PROFILE fixed_ke t i cell_t c real x ND_ND 2 80 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros real r begin_c_loop c t centroid is defined to specify position dependent profiles C_CENTROID x c t r x 1 F_PROFILE c t i ka1 ka2 r ka3 r r ka4 r r r ka5 r r r r ka6 r xr r r r end_c_loop c t Example 4 Wall Heat Generation Rate Profile The following UDF named wallheatgenerate generates a heat generation rate profile for a planar conduction wall After it has been interpreted or compiled you can activate this UDF in the Wall boundary conditions dialog box in ANSYS FLUENT Wall Heat Generation Rate Profile UDF include udf h DEFINE_PROFILE wallheatgenerate thread i real source 0 001 face_t f begin_f_loop f thread F_PROFILE f thread i source end_f_loop f thread Release 12 0 ANSYS Inc January 26 2009 2 81 DEFINE Macros Example 5 Beam Direction Profile at Semi Transparent Walls The following UDF named q_nx where x is the direction vector i j k specifies the beam direction normal to every face on the cylinder After it has been interpreted or compiled you can activate this UDF in the Wall boundary conditions dialog box in ANSYS FLUENT Beam Direction Profile UDF at Semi Transparent Walls includ
88. Figure 6 4 12 in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box eee beeen Edit Discrete Phase Model Interaction Particle Treatment C Interaction with Continuous Phase _ Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force Number of Scalars 4 none i Scalar Update none Source fdpm_source tlibudF DPM Time Step none i Figure 6 4 12 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the UDF tab in the Discrete Phase Model dialog box Select the function name e g dpm_source libudf from the Source drop down list under User Defined Functions Figure 6 4 12 and click OK See Section 2 5 11 DEFINE_DPM_SOURCE for details about DEFINE_DPM_SOURCE functions 6 76 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 12 Hooking DEFINE_DPM_SPRAY_COLLIDE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SPRAY_COLLIDE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model dialog box Figure 6 4 13 in ANSYS FLUENT To hook the UDF first
89. File in Your Source File The udf h header file contains definitions for DEFINE macros as well as include compiler directives for C library function header files It also includes header files e g mem h for other ANSYS FLUENT supplied macros and functions You must therefore include the udf h file at the beginning of every UDF source code file using the include compiler directive include udf h For example when udf h is included in the source file containing the DEFINE statement from the previous section include udf h DEFINE_PROFILE inlet_x_velocity thread index upon compilation the macro will expand to void inlet_x_velocity Thread thread int index a You do not need to put a copy of udf h in your local folder when you compile your UDF The ANSYS FLUENT solver automatically reads the udf h file from the following folder after your UDF is compiled path ANSYS Inc v120 fluent fluent12 0 i ere where path is the folder in which you have installed ANSYS FLUENT by de fault the path is C Program Files and z is replaced by the appropriate number for the release e g 9 for fluent12 0 9 Release 12 0 ANSYS Inc January 26 2009 1 5 Overview 1 5 Interpreting and Compiling UDFs Source code files containing UDFs can be either interpreted or compiled in ANSYS FLU ENT In both cases the functions are compiled but the way in which the source code is compiled and the code that results from th
90. ID and the partition ID are different For example in a parallel system with two compute nodes 0 and 1 the exterior cells of compute node 0 have a partition ID of 1 and the exterior cells of compute node 1 have a partition ID of 0 Figure 7 5 4 Boundary zone face Node ID Partition ID Partition boundary face Partition ID set to same or different Node ID using Fill macros Interior face Node ID Partition ID Interior cells Exterior cells Node ID Partition ID Node ID and Partition ID different Figure 7 5 4 Partition Ids for Cells and Faces in a Compute Node 7 27 Release 12 0 ANSYS Inc January 26 2009 Parallel Considerations Face Partition IDs For interior faces and boundary zone faces the partition ID is the same as the compute node ID The partition ID of a partition boundary face however can be either the same as the compute node or it can be the ID of the adjacent node depending on what values F_PART is filled with Figure 7 5 4 Recall that an exterior cell of a compute node has only partition boundary faces the other faces of the cell belong to the adjacent compute node Therefore depending on the computation you want to do with your UDF you may want to fill the partition boundary face with the same partition ID as the compute node using Fill_Face_Part_With_Same or with different IDs using Fill Face Part With Different Face partition IDs will need to be filled before you can acc
91. Inc January 26 2009 6 5 Hooking Dynamic Mesh UDFs Dynamic Mesh Zones ace default interior stage libudf Figure 6 5 6 The Dynamic Mesh Zones Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 89 Hooking UDFs to ANSYS FLUENT 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs This section contains methods for hooking anisotropic diffusion coefficient flux and un steady UDFs for scalar equations that have been defined using DEFINE macros described in Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros and in terpreted or compiled using methods described in Chapters 4 or 5 respectively See Section 6 2 15 Hooking DEFINE_PROFILE UDF Section 6 2 19 Hooking DEFINE_SOURCE UDFs and Section 6 2 3 Hooking DEFINE_DIFFUSIVITY UDFs to hook scalar source term profile or isotropic diffusion coefficient UDFs 6 6 1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_ANISOTROPIC_DIFFUSIVITY UDF the name of the function you supplied as the first DEFINE macro argument will become visible and selectable in ANSYS FLUENT To hook the UDF to ANSYS FLUENT you will first need to open the User Defined Scalars dialog box Define User Defined gt Scalars In the User Defined Scalars dialog box specify the Number of User Defined Scalars e g 2 an
92. January 26 2009 2 5 DEFINE Macros Example 2 The following UDF named adjust_fcn specifies a user defined scalar as a function of the gradient of another user defined scalar using DEFINE_ADJUST The function is called once every iteration It is executed as a compiled UDF in ANSYS FLUENT k k k k k 2k CCK 2k 2k 2k 2K 2K I 2K k 2k A 2K K 2K FK FK 2K 2K 2K K 2K 2K AK 2K 2K 2K 2K 2K a KK 2K K K K 2 2k 2K FK K K K KK K K 2k k K UDF for defining user defined scalars and their gradients EEEE ooo oo kkk kkk k kkk kk kkk include udf h DEFINE_ADJUST adjust_fcn d Thread t cell_t c real K_EL 1 0 Do nothing if gradient isn t allocated yet if Data_Valid_P return thread_loop_c t d if FLUID_THREAD_P t begin_c_loop_all c t C_UDSI c t 1 K_EL NV_MAG2 C_UDSI_G c t 0 C_VOLUME c t end_c_loop_all c t Hooking an Adjust UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE ADJUST is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g adjust_fcn will become visible and selectable via the User Defined Function Hooks dialog box in ANSYS FLUENT Note that you can hook multiple adjust functions to your model See Section 6 1 1 Hook ing DEFINE_ADJUST UDFs for details 2 6 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose
93. May 2003 Modified Rana Faltsi Date December 2006 DOC OOOO OOO OOOO A kk kkk kkk OPTIONAL REFERENCE OFFSET VALUES FOR ENTHALPY AND ENTROPY define H_REF 0 0 define S_REF 0 0 FUNCTION RKEOS_pressure of species i Returns pressure given T and density double RKEOS_pressure double temp double density int i double v 1 density double afun a0 i pow tcrit i temp nrk i return rgas i temp v bb i afun v v b0 i Release 12 0 ANSYS Inc January 26 2009 8 87 Examples FUNCTION RKEOS_spvol of species i Returns specific volume given T and P double RKEOS_spvol double temp double press int i double ai a2 a3 double vv vvi vv2 vv3 double qq qq3 sqq rr tt dd double afun a0 i pow tcrit i temp nrk i al cOli rgas i temp press a2 bb i b0 i rgas i temp b0 i press afun press a3 afun bb i press Solve cubic equation for specific volume qq al xai 3 a2 9 rr 2 al al ai 9 al a2 27 a3 54 qq3 qq qq qq dd qq3 rr rr If dd lt 0 then we have one real root If dd gt 0 then we have three roots gt choose largest root if dd lt 0 tt SIGN rr
94. Note that FLUID_THREAD_P t assumes that the thread is a cell thread For example FLUID_THREAD_P t0 returns TRUE if the thread pointer tO passed as an argument represents a fluid thread NULLP amp NNULLP You can use the NULLP and NNULLP functions to check whether storage has been allocated for user defined scalars NULLP returns TRUE if storage is not allocated and NNULLP returns TRUE if storage is allocated Below are some examples of usage NULLP T_STORAGE_R_NV tO SV_UDSI_G p1 NULLP returns TRUE if storage is not allocated for user defined storage variable NNULLP T_STORAGE_R_NV t0 SV_UDSI_G p1 NNULLP returns TRUE if storage is allocated for user defined storage variable Release 12 0 ANSYS Inc January 26 2009 3 81 Additional Macros for Writing UDFs MPI The macro M_PI returns the value of r UNIVERSAL_GAS_CONSTANT UNIVERSAL_GAS_CONSTANT returns the value of the universal gas constant 8314 34 J Kmol K EA Note that this constant is not expressed in SI units See Section 2 3 27 DEFINE_VR_RATE for an example UDF that utilizes UNIVERSAL_GAS_CONSTANT SQR k SQR k returns the square of the given variable k or k x k 3 82 Release 12 0 ANSYS Inc January 26 2009 Chapter 4 Interpreting UDFs After you have written your UDF using any text editor and have saved the source code file it with a c extension in your working folder you are ready to interpret the source fi
95. PEMDAS is not followed in vector functions Instead the underscore _ sign is used to group operands into pairs so that operations are performed on the elements of pairs before they are performed on groups Note that all of the vector utilities in this section have been designed to work correctly in 2D and 3D Consequently you don t need to do any testing to determine this in your UDF 3 4 1 Macros for Dealing with Two and Three Dimensions There are two ways that you can deal with expressions involving two and three dimensions in your UDF The first is to use an explicit method to direct the compiler to compile separate sections of the code for 2D and 3D respectively This is done using RP_2D and RP_3D in conditional if statements The second method allows you to include general 3D expressions in your UDF and use ND and NV macros that will remove the z components when compiling with RP_2D NV macros operate on vectors while ND macros operate on separate components RP_2D and RP_3D The use of a RP_2D and RP_3D macro in a conditional if statement will direct the compiler to compile separate sections of the code for 2D and 3D respectively For example if you want to direct the compiler to compute swirl terms for the 3D version of ANSYS FLUENT only then you would use the following conditional compile statement in your UDF if RP_3D compute swirl terms endif 3 4 2 The ND Macros The use of ND macros in a UDF allows you to
96. Rate in the UDF Rate group box for that pathway and then click Apply Repeat this process for all of the remaining NO pathways Unless specifically defined in your NO rate UDF data and parameter settings for each individual NO pathway will be derived from the settings in the NOx Model dialog box Therefore it is good practice to make the appropriate settings in the NOx Model dialog box even though you may use a UDF to replace the default rates with user specified rates There is no computational penalty for doing this because the default rate calculations will be ignored when Replace FLUENT Rate is selected To specify a custom maximum limit Tmax for the integration of the temperature PDF for each cell you must first select the UDF name e g user_nox libudf from the NOx Rate drop down list as described previously Then click the Turbulence Interaction Mode tab and select either temperature or temperature species from the PDF Mode drop down list Finally select user defined from the Tmax Option drop down list and click Apply See Section 2 3 12 DEFINE_NOX_RATE for details about defining DEFINE_NOX_RATE func tions 6 2 13 Hooking DEFINE _PR_RATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE PR RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 1
97. Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples In addition to compiling this UDF as described in Chapter 5 Compiling UDFs you will need to enable the solution of a user defined scalar transport equation in ANSYS FLUENT Define User Defined Scalars See Section 1 3 User Defined Scalar UDS Transport Equations in the separate Theory Guide for UDS equation theory and details on how to setup scalar equations Implementing ANSYS FLUENT s P 1 Radiation Model Using User Defined Scalars This section provides an example that demonstrates how the P1 radiation model can be implemented as a UDF utilizing a user defined scalar transport equation In the P1 model the variation of the incident radiation G in the domain can be described by an equation that consists of a diffusion and source term The transport equation for incident radiation G is given by Equation 8 2 5 The diffusion coefficient I is given by Equation 8 2 6 and the source term is given by Equation 8 2 7 See Section 5 3 3 P 1 Radiation Model Theory in the separate Theory Guide for more details V TVG Sf 0 8 2 5 r 8 2 6 8a 3 C a ee So a 4o7 G 8 2 7 The boundary condition for G at the walls is equal to the negative of the radiative wall heat flux qrw Equation 8 2 8 where 7 is the outward normal vector see Sec tion 5 3 3 P 1 Radiation Model Theory in the separate Theory Gui
98. Special Macros for details Release 12 0 ANSYS Inc January 26 2009 1 11 Overview 1 9 UDF Calling Sequence in the Solution Process UDFs are called at predetermined times in the ANSYS FLUENT solution process How ever they can also be executed asynchronously or on demand using a DEFINE_ON_DEMAND UDF If a DEFINE_EXECUTE_AT_END UDF is utilized then ANSYS FLUENT calls the func tion at the end of an iteration A DEFINE_EXECUTE_AT_EXIT is called at the end of an ANSYS FLUENT session while a DEFINE_EXECUTE_ON_LOADING is called whenever a UDF compiled library is loaded Understanding the context in which UDFs are called within ANSYS FLUENT s solution process may be important when you begin the process of writing UDF code depending on the type of UDF you are writing The solver contains call outs that are linked to user defined functions that you write Knowing the sequenc ing of function calls within an iteration in the ANSYS FLUENT solution process can help you determine which data are current and available at any given time Pressure Based Segregated Solver The solution process for the pressure based segregated solver Figure 1 9 1 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the ANSYS FLUENT user interface Next PROFILE UDFs are called followed by a call to INIT UDFs Init
99. The utility NV_VV performs operations on vector elements The operation that is per formed on the elements depends upon what symbol is used as an argument in place of the signs in the following macro call NV_VV a x y 2D a 0 x 0 y 0 afi x 1 y 1 See Section 2 6 4 DEFINE_GRID_MOTION for an example UDF that utilizes NV_VV NV_V_VS The utility NV_V_VS adds a vector to another vector which is multiplied by a scalar NV_V_VS a x y 0 5 2D a 0 x 0 y 0 0 5 alt x 1 y 1 0 5 Note that the sign can be replaced by or and the sign can be replaced by Release 12 0 ANSYS Inc January 26 2009 3 71 Additional Macros for Writing UDFs NV_VS_VS The utility NV_VS_VS adds a vector to another vector which are each multiplied by a scalar NV_VS_VS a x 2 0 y 0 5 2D a 0 x 0 2 0 y 0 0 5 a 1 x 1 2 0 y 1 0 5 Note that the sign can be used in place of or and the sign can be replaced by 3 4 4 Vector Operation Macros There are macros that you can use in your UDFs that will allow you to perform oper ations such as computing the vector magnitude dot product and cross product For example you can use the real function NV_MAG V to compute the magnitude of vector V Alternatively you can use the real function NV_MAG2 V to obtain the square of the magnitude of vector V Vector Magnitude Using NV_MAG a
100. Therefore if a subdomain pointer is available in your UDF it is recom mended that the DOMAIN_SUPER_DOMAIN macro be used instead of the Get_Domain macro to avoid potential incompatibility issues with future releases of ANSYS FLUENT Mixture Thread Pointer THREAD SUPER THREAD You can use the THREAD_SUPER_THREAD macro when your UDF has access to a particular phase level thread subthread pointer and you want to retrieve the mixture level thread pointer THREAD_SUPER_THREAD has one argument subthread Thread subthread Thread mixture_thread THREAD_SUPER_THREAD subthread subthread is a pointer to a particular phase level thread within the multiphase mixture It is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a thread variable argument e g DEFINE_PROFILE and the function is hooked to a primary or secondary phase in the mixture Note that THREAD SUPER_THREAD is similar in implementation to the DOMAIN SUPER DOMAIN macro described in Section 3 3 2 Mixture Domain Pointer DOMAIN_SUPER_DOMAIN Domain ID DOMAIN_ID You can use DOMAIN_ID when you want to access the domain_id that corresponds to a given phase level domain pointer DOMAIN_ID has one argument subdomain which is the pointer to a phase level domain The default domain_id value for the top level domain mixture is 1 That is if the domain pointer that is passed to DOMAIN_ID is the mixture level domain pointer t
101. Tracked_Particle p p p p p p p evaporating species index in mixture devolatilizing species index in mixture oxidizing species index in mixture combustion products species index in mixture current particle law index next particle law index storage array for user defined values indexed by i 3 38 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Table 3 2 31 Macros for Particle Material Properties Defined in dpm h Macro Argument Types Returns P_MATERIAL p DPM_BOILING_TEMPERATURE p m DPM_CHAR_FRACTION p DPM_DIFFUSION_COEFF p t DPM_EMISSIVITY p m DPM_EVAPORATION_ DPM_HEAT_OF_PYROLYSIS p DPM_HEAT_OF_REACTION p DPM_LATENT_HEAT p DPM_LIQUID_SPECIFIC_HEAT pst DPM_MU p DPM_SCATT_FACTOR p m DPM_SPECIFIC_HEAT p t DPM_SWELLING_COEFF p DPM_SURFTEN p DPM_VAPOR_PRESSURE p m DPM_VAPOR_TEMP p m DPM_VOLATILE_FRACTION p Tracked Particle p Tracked_Particle p Material m Tracked_Particle p Tracked_Particle p particle temperature t Tracked_Particle Material m Tracked Particle TEMPERATURE p m Tracked_Particle Tracked_Particle Tracked_Particle p Tracked Particle p particle temperature t Note particle temp typically determined by P_T p Tracked_Particle p p p p p Tracked_Particle p Material m Tracked_Particle p particle temperature t Note particle tem perat
102. UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Custom Laws dialog box in ANSYS FLUENT See Section 6 4 7 Hooking DEFINE DPM LAW UDFs for details on how to hook your DEFINE _DPM_LAW UDF to ANSYS FLUENT 2 1 82 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 8 DEFINE_DPM_OUTPUT Description You can use DEFINE_DPM_OUTPUT to modify what is written to the sampling device output This function allows access to the variables that are written as a particle passes through a sampler see Chapter 23 Modeling Discrete Phase in the separate User s Guide for details Usage DEFINE DPM OUTPUT name header fp p t plane Argument Type Description symbol name UDF name int header Variable that is equal to 1 at the first call of the function before particles are tracked and set to 0 for subsequent calls FILE fp Pointer to the file to or from which you are writing or reading Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked Thread t Pointer to the thread that the particle is passing through if the sampler is represented by a mesh surface If the sampler is not defined as a mesh surface then the value of t is NULL Plane plane Pointer to the Plane structure see dpm h if the sampling device is defined as a planar slice line in 2d If a mesh surface i
103. Vars The new capability of loading more than one UDF library into ANSYS FLUENT raises the possibility of user defined scalar UDS clashes To avoid data contention between multiple UDF libraries using the same user defined scalars ANSYS FLUENT has provided the macro Reserve_User_Scalar_Vars that allows you to reserve scalars prior to use int Reserve_User_Scalar_Vars int num int num is the number of user defined scalars that the library uses The integer returned is the lowest UDS index that the library may use After calling offset Reserve_User_Scalar_Vars int num the library may safely use C_UDSI c t offset to CUDSI c t offsettnum 1 See Section 2 2 6 DEFINE EXECUTE ON LOADING for an example of macro usage Note that there are other methods you can use within UDFs to hardcode the offset to prevent data contention Reserve User_Scalar_Vars defined in sg_udms h is designed to be called from an EXECUTE_ON_ LOADING UDF Section 2 2 6 DEFINE EXECUTE_ON_ LOADING An on loading UDF as its name implies executes as soon as the shared library is loaded into AN SYS FLUENT The macro can also be called from an INIT or ON DEMAND UDF After a user scalar has bee reserved it can be set to unique names for the particular library using Set_User_Memory_Name see below for details on Set_User_Memory_Name After the number of UDS that are needed by a particular library is set in the GUI and the variables are successfully reserved for the lo
104. _G suffix are non limited values and if used to reconstruct values within the cell at faces for example may potentially result in values that are higher or lower than values in the surrounding cells Therefore if your UDF needs to compute face values from cell gradients you should use the reconstruction gradient RG values instead of non limited gradient G values Reconstruction gradient variables are identified by the suffix _RG and use the limiting method that you have activated in your ANSYS FLUENT model to limit the cell gradient values Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Gradient G Vector Macros Table 3 2 9 shows a list of cell gradient vector macros Note that gradient variables are available only when the equation for that variable is being solved For example if you are defining a source term for energy your UDF can access the cell temperature gradient using C_T_G but it cannot get access to the x velocity gradient using C_U_G The reason for this is that the solver continually removes data from memory that it doesn t need In order to retain the gradient data when you want to set up user defined scalar transport equations for example you can prevent the solver from freeing up memory by issuing the text command solve set expert and then answering yes to the question Keep temporary solver memory from being freed Note that when you do this all of the gradient data is retained
105. a DPM Initialization UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_INJECTION_INIT is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Set Injection Properties dialog box in ANSYS FLUENT See Section 6 4 6 Hooking DEFINE_DPM_INJECTION_INIT UDFs for details on how to hook your DEFINE_DPM_INJECTION_INIT UDF to ANSYS FLUENT 2 1 80 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 7 DEFINE_DPM_LAW Description You can use DEFINE DPM LAW to customize laws for particles For example your UDF can specify custom laws for heat and mass transfer rates for droplets and combusting particles Additionally you can specify custom laws for mass diameter and temperature properties as the droplet or particle exchanges mass and energy with its surroundings Usage DEFINE DPM LAW name p ci Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked int ci Variable that indicates whether the continuous and discrete phases are coupled equal to 1 if coupled with continuous phase 0 if not coupled Function returns void There are three arguments to DEFINE_DPM_LAW name p and ci You supply name the name of the UDF
106. a fixed value profile UDF for fluid boundaries Fixed value UDFs are defined using the DEFINE_PROFILE macro See Section 2 3 15 DEFINE_PROFILE for details Additional pre defined macros that you can use for coding scalar transport equation UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros 2 226 Release 12 0 ANSYS Inc January 26 2009 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros Wall Inflow and Outflow Boundary Condition UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply a specified value or flux UDF for all wall inflow and outflow boundaries Wall inflow and outflow boundary UDFs are defined using the DEFINE PROFILE macro Section 2 3 15 DEFINE_PROFILE Additional pre defined macros that you can use for coding scalar transport equation UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros 2 7 2 DEFINE_ANISOTROPIC_DIFFUSIVITY Description You can use DEFINE_ANISOTROPIC_DIFFUSIVITY to specify an anisotropic diffusivity for a user defined scalar UDS transport equation See Section 8 6 2 Anisotropic Diffusion in the separate User s Guide for details about anisotropic diffusivity material properties in ANSYS FLUENT Usage DEFINE_ANISOTROPIC_DIFFUSIVITY name c t i dmatrix Argument Type Description symbol name UDF name cellt c
107. amp ee ew bee bw Gree Ss 2 189 20 11 DEFINE DPM SOURCE 2 362244 40844405 Gud ee ada 2 193 20 12 DEFINE DPM SPRAY COLLIDE 4 cis p m siap ek de wee Ea SS 2 194 2013 DEFINE DPM SWITCH 2 tase bee nee ee hee Re E i a 2 196 29 14 DEFINE DPM TIMESTEP o sek co e SRR oi E e SE ERG 2 202 2 50 15 DEFINE DPM VP_EQUILIB s c s ra acta d a ea 4 Ew a a 2 205 Release 12 0 ANSYS Inc January 26 2009 IlI CONTENTS 2 0 Dynamic Mesh DEFINE Macros cc 2a dd eee ed eee eee ee eS 2 208 20 1 DEFINE CG MOTION 3 2 4 68 ar oaan E a E a a Be Ble 2 209 2 6 2 DEFINE DYNAMIC_ZONE PROPERTY 2 211 20 3 DEFINE GEOM 2 24 2 8 ecko Wek H Bo eM Sw ch aS A 4 2 216 DOA DEFINE GRID MOTION osre gi 6 woul ee eo ee be gd ee ow A 2 218 2 6 5 DEFINE_SDOF_PROPERTIES 0 000 eens 2 221 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 225 Otel Miroduction e sce gir 8 6 Oe 8 Ge k a e eS hw SH Gree 2 225 2 7 2 DEFINE ANISOTROPIC DIFFUSIVITY 2 2c kee catt taat 2 227 2 9 DEFINE UDS FLUX a s dara ce eG a ee em eee ew wR e a 2 230 274 DEFINE UDS UNSTEADY co cr bee doe wed a Ke a ee 2 234 3 Additional Macros for Writing UDFs 3 1 Gol AMMO ece eda nes ra Dedede ee hee eee SERE EE ES 3 1 32 Data Access Macros scoe che dae Pees He a Oo we ow oe Ss 3 4 3 2 1 Axisymmetric Considerations for Data Access Macros 3 4 322 Node Ma s scs se mossa REDE momia a Eee OSES 3 5 oe CUMIOS es as ee OS ee SA E
108. an integer that defines the number of elements in the array The index of a C array always begins at 0 Arrays of variables can be of different data types as shown below Examples int a 10 b 10 10 real radii 5 a 0 1 a 1 Dimensional array of variable a radiil4 3 14159265 a 1 Dimensional array of variable radii b 10 10 4 a 2 Dimensional array of variable b A 10 Pointers A pointer is a variable that contains an address in memory where the value referenced by the pointer is stored In other words a pointer is a variable that points to another variable by referring to the other variable s address Pointers contain memory addresses not values Pointer variables must be declared in C using the notation Pointers are widely used to reference data stored in structures and to pass data among functions by passing the addresses of the data For example int ip declares a pointer named ip that points to an integer variable A 8 Release 12 0 ANSYS Inc January 26 2009 A 10 Pointers Now suppose you want to assign an address to pointer ip To do this you can use the amp notation For example ip amp a assigns the address of variable a to pointer ip You can retrieve the value of variable a that pointer ip is pointing to by xip Alternatively you can set the value of the variable that pointer ip points For example xip 4 assigns a value of 4 to the variable that p
109. and UNIX Linux systems are differ ent so the procedure for setting up the folder directory structure is described separately for each Windows Systems For compiled UDFs on Windows systems two ANSYS FLUENT files are required to build your shared UDF library makefile_nt udf and user_nt udf The file user_nt udf has a user modifiable section that allows you to specify source file parameters The procedure below outlines steps that you need to follow in order to set up the folder structure required for the shared library 1 In your working folder make a folder that will store your UDF library e g libudf 2 Make a folder below this called src 3 Put all your UDF source files into this folder e g Libudf src 4 Make an architecture folder below the library folder called ntx86 or win64 for Intel systems running Windows e g Libudf ntx86 5 10 Release 12 0 ANSYS Inc January 26 2009 5 3 Compile a UDF Using the TUI 5 In the architecture folder e g libudf ntx86 create folders for the ANSYS FLU ENT versions you want to build for your architecture e g ntx86 2d and ntx86 3d Possible versions are 2d or 3d single precision serial 2D or 3D 2ddp or 3ddp double precision serial 2D or 3D 2d_node and 2d_host single precision parallel 2D 3d_node and 3d_host single precision parallel 3D 2ddp_node and 2ddp host double precision parallel 2D 3ddp_node and 3ddp_host double precision parallel 3D Note that you mu
110. be used to obtain the real centroid of a face F_CENTROID finds the coordinate position of the centroid of the face f and stores the coordinates in the x array Note that the x array is always one dimensional but it can be x 2 or x 3 depending on whether you are using the 2D or 3D solver Table 3 2 20 Macro for Face Centroids Defined in metric h Macro Argument Types Outputs F_CENTROID x f t real x ND_ND face_t f Thread t x face centroid 3 22 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros The ND_ND macro returns 2 or 3 in 2D and 3D cases respectively as defined in Sec tion 3 4 2 The ND Macros Section 2 3 15 DEFINE_PROFILE contains an example of F_CENTROID usage Face Area Vector F_AREA F_AREA can be used to return the real face area vector or face area normal of a given face f in a face thread t See Section 2 7 3 DEFINE UDS FLUX for an example UDF that utilizes F_AREA Table 3 2 21 Macro for Face Area Vector Defined in metric h Macro Argument Types Outputs F_AREA A f t ALND_ND facet f Thread t A area vector By convention in ANSYS FLUENT boundary face area normals always point out of the domain ANSYS FLUENT determines the direction of the face area normals for interior faces by applying the right hand rule to the nodes on a face in order of increasing node number This is shown in Figure 3 2 1 1 A e using Right Hand
111. before continuing See Section 5 6 Common Errors When Building and Loading a UDF Library for a list of common errors 5 Click Load to load the shared library into ANSYS FLUENT The console will report that the library has been opened and the function e g inlet_x_velocity loaded Opening library libudf Library libudf ntx86 2d libudf dll opened inlet_x_velocity Done See Chapter 5 Compiling UDFs for more information on the compile build process 8 1 6 Step 5 Hook the UDF to ANSYS FLUENT Now that you have interpreted or compiled your UDF following the methods outlined in Step 4 you are ready to hook the profile UDF in this sample problem to the Velocity Inlet boundary condition dialog box see Chapter 6 Hooking UDFs to ANSYS FLUENT for details on how to hook UDFs First click the Momentum tab in the Velocity Inlet dialog box Figure 8 1 8 and then choose the name of the UDF that was given in our sample problem with udf preceding it udf inlet_x_velocity from the X Velocity drop down list Click OK to accept the new boundary condition and close the dialog box The user profile will be used in the subsequent solution calculation Release 12 0 ANSYS Inc January 26 2009 8 11 Examples gt EME velocity inlet Edit Velocity Inlet Zone Name velocity inlet Momentum Thermal Radiation Species DPM multiphase UDS velocity Specification Method Components Reference Fra
112. begin_c_loop c t volume C_VOLUME c t get cell volume temp C_T c t get cell temperature if temp lt tmin tmin 0 tmin temp if temp gt tmax tmax 0 tmax temp vol_tot volume tavg temp volume end_c_loop c t tavg vol_tot printf n Tmin g Tmax g Tavg g n tmin tmax tavg Release 12 0 ANSYS Inc January 26 2009 2 21 DEFINE Macros Compute temperature function and store in user defined memory location index 0 begin_c_loop c t temp C_T c t C_UDMI c t 0 temp tmin tmax tmin end_c_loop c t Get_Domain is a macro that retrieves the pointer to a domain It is necessary to get the domain pointer using this macro since it is not explicitly passed as an argument to DEFINE ON DEMAND The function named on_demand_calc does not take any explicit arguments Within the function body the variables that are to be used by the function are defined and initialized first Following the variable declarations a looping macro is used to loop over each cell thread in the domain Within that loop another loop is used to loop over all the cells Within the inner loop the total volume and the minimum maximum and volume averaged temperature are computed These computed values are printed to the ANSYS FLUENT console Then a second loop over each cell is used to compute the function f T and store it in user defined memory location 0 Re
113. cell zone that you define in your ANSYS FLUENT model in a boundary conditions dialog box has an integer Zone ID that is associated with the data contained within the zone You will not see the term thread in a graphics dialog box in ANSYS FLUENT so you can think of a zone as being the same as a thread data structure when programming UDFs Cells and cell faces are grouped into zones that typically define the physical components of the model e g inlets outlets walls fluid regions A face will bound either one or two cells depending on whether it is a boundary face or an interior face A domain is a data structure in ANSYS FLUENT that is used to store information about a collection of node face threads and cell threads in a mesh node cell center simple 3D grid Figure 1 7 1 Mesh Components Release 12 0 ANSYS Inc January 26 2009 1 9 Overview node mesh point node thread grouping of nodes edge boundary of a face 3D face boundary of a cell 2D or 3D face thread grouping of faces cell control volume into which domain is broken up cell center location where cell data is stored cell thread grouping of cells domain a grouping of node face and cell threads 1 8 Data Types in ANSYS FLUENT In addition to standard C language data types such as real int etc that can be used to define data in your UDF there are ANSYS FLUENT specific data types that are associated with solver data These
114. contains the UDF used to model the reaction taking place in the porous region is shown below The function named vol_reac_rate is defined on a cell for a given species mass fraction using DEFINE_VR_RATE The UDF performs a test to check for the porous region and only applies the reaction rate equation to the porous region The macro FLUID_THREAD_P t is used to determine if a cell thread is a fluid rather than a solid thread The variable THREAD_VAR t fluid porous is used to check if a fluid cell thread is a porous region DCO OO OO IR 2K 2K I 2K 2K A FKK RK 2K K K FK 2 24 2k 2k 2k K 2k 2K 2k K 2k gt K rate c Compiled UDF for specifying a reaction rate in a porous medium BE AAR I I CIARA RI A A A 2k KK KK KEK A ACA A A KK KK AAA 2K 2k 2k 2K k kkk kk include udf h define K1 2 0e 2 define K2 5 DEFINE_VR_RATE vol_reac_rate c t r mole_weight species_mf rate rr_t real s1 species_mf 0 real mw1 mole_weight 0 if FLUID_THREAD_P t amp amp THREAD_VAR t fluid porous xrate K1 s1 pow 1 K2 s1 2 0 mw1 else xrate 0 xrr_t rate This UDF is executed as a compiled UDF in ANSYS FLUENT Follow the procedure for compiling source files using the Compiled UDFs dialog box that is described in Sec tion 5 2 Compiling a UDF Using the GUI After the function vol reac rate is compiled and loaded you can hook the reaction rate UDF to ANSYS FLUENT by selecting the function s name in the Volume Reactio
115. d make k gt makelog 2 gt amp 1 cat makelog a done linking to myudf c in 1nx86 2d Release 12 0 ANSYS Inc January 26 2009 5 17 Compiling UDFs building library in 1nx86 2d make 1 Entering directory udf_names c Generating udf_names make 2 Entering directory profile c make libudf so Compiling udf_names o Compiling profile o Linking libudf so make 2 Leaving directory udf_names c make 1 Leaving directory profile c You can also see the log file in the working directory for compilation history Done 5 3 3 Load the UDF Library You can load the shared library you compiled and built using the GUI from the Compiled UDFs dialog box or the UDF Library Manager dialog box Follow the procedure outlined in Step 9 of Section 5 2 Compiling a UDF Using the GUI or in Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box respectively 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources ANSYS FLUENT allows you to build a shared library for precompiled object files that are derived from external sources using the text user interface TUI option For example you can link precompiled objects derived from FORTRAN sources 0 objects from f sources to ANSYS FLUENT for use by a UDF The following sections describe the procedures for doing this on a Windows system and a UNIX Linux system Windows Systems 1 Follow the
116. defined GUI and represent the possible user options available from the GUI dialog box A different C function in UDF can be called for each option For example the user defined GUI dialog box may have a number of buttons Each button may be represented by different integers which when clicked will execute a corresponding C function i DEFINE_EXECUTE_FROM_GUI UDFs must be implemented as compiled UDFs and there can be only one function of this type in a UDF library Release 12 0 ANSYS Inc January 26 2009 2 11 DEFINE Macros Example The following UDF named reset_udm resets all user defined memory UDM values when a reset button on a user defined GUI dialog box is clicked The clicking of the button is represented by 0 which is passed to the UDF by the ANSYS FLUENT solver pRa oo oo o kkk kkk kkk 21 21 24 k 24 2 UDF called from a user defined GUI dialog box to reset all user defined memory locations EEEE ooo ooo ok kkk kk k kkk k include udf h DEFINE_EXECUTE_FROM_GUI reset_udm myudflib mode Domain domain Get_Domain 1 Get domain pointer Thread t cell_t c int i Return if mode is not zero if mode 0 return Return if no User Defined Memory is defined in ANSYS FLUENT if n_udm 0 return Loop over all cell threads in domain thread_loop_c t domain Loop over all cells begin_c_loop c t q Set all UDMs to zero for i 0 i lt n_udm i
117. defined in the header file sg_nox h which is included in udf h They can be used to return real SO variables in SI units and are available in both the pressure based and the density based solver See Section 2 3 20 DEFINE_SOX_RATE for examples of DEFINE_SOX_RATE UDFs that utilize these macros Release 12 0 ANSYS Inc January 26 2009 3 41 Additional Macros for Writing UDFs Table 3 2 33 Macros for SO UDFs Defined in sg_nox h Macro Returns POLLUT_EQN Pollut Par MOLECON Pollut SPE NULLIDX Pollut_Par SPE ARRH Pollut K POLLUT_FRATE Pollut POLLUT_RRATE Pollut POLLUT_FLUCTDEN Pollut POLLUT_FLUCTTEM Pollut POLLUT_FLUCTYI Pollut SPE POLLUT_CTMAX Pollut Par index of pollutant equation being solved see below molar concentration of species specified by SPE see below TRUE if the species specified by SPE doesn t exist in ANSYS FLUENT case i e in the Species dialog box Arrhenius rate calculated from the constants specified by K see below production rate of the pollutant species being solved reduction rate of the pollutant species being solved fluctuating density value or if no PDF model is used mean density at a given cell fluctuating temperature value or if no PDF model is used mean temperature at a given cell fluctuating mass fraction value or if no PDF model is used mean mass fraction at a given cell of the species given by index SPE uppe
118. defined scalar boundary value DEFINE_PROFILE mixture discrete phase boundary condition DEFINE_PROFILE mixture Release 12 0 ANSYS Inc January 26 2009 C 1 Quick Reference Guide for Multiphase DEFINE Macros Table C 1 2 DEFINE Macro Usage for the VOF Model Variable Macro Phase Specified On Fluid mass source DEFINE SOURCE primary and secondary phase s momentum source DEFINE_SOURCE mixture energy source DEFINE_SOURCE mixture turbulence kinetic energy source DEFINE_SOURCE mixture turbulence dissipation rate source DEFINE_SOURCE mixture user defined scalar source DEFINE SOURCE mixture species source DEF INE_SOURCE phase dependent velocity DEF INE_PROFILE mixture temperature DEFINE_PROFILE mixture user defined scalar DEFINE PROFILE mixture turbulence kinetic energy DEFINE PROFILE mixture turbulence dissipation rate DEFINE_PROFILE mixture species mass fraction DEFINE_PROFILE phase dependent porosity DEF INE_PROFILE mixture Boundary Conditions Wall species boundary condition internal emissivity irradiation roughness height roughness constant shear stress components swirl components moving velocity components heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature user scalar boundary value discrete phase boundary value DEF INE_PROFILE DEFINE PROFILE DEF INE_PROFILE DEFINE_PROFI
119. dialog box in ANSYS FLUENT See Section 6 4 12 Hooking DEFINE DPM SPRAY COLLIDE UDFs for details on how to hook your DEFINE_DPM_SPRAY_COLLIDE UDF to ANSYS FLUENT 2 5 13 DEFINE_DPM_SWITCH Description You can use DEFINE DPM SWITCH to modify the criteria for switching between laws The function can be used to control the switching between the user defined particle laws and the default particle laws or between different user defined or default particle laws 2 1 96 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros Usage DEFINE DPM SWITCH name p ci Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked int ci Variable that indicates if the continuous and discrete phases are coupled equal to 1 if coupled with continuous phase 0 if not coupled Function returns void There are three arguments to DEFINE_DPM_SWITCH name p and ci You supply name the name of the UDF p and ci are variables that are passed by the ANSYS FLUENT solver to your UDF Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following is an example of a compiled UDF that uses DEFINE_DPM_SWITCH to switch between DPM laws using a criterion The UDF switches to D
120. e g udfexample c in your working folder See Appendix A for some basic information on C programming After you have written the C function you are ready to start ANSYS FLUENT and read in or set up your case file Step 3 You will then need to interpret or compile the source code debug it Step 4 and then hook the function to ANSYS FLUENT Step 5 Finally you ll run the calculation Step 6 analyze the results from your simulation and compare them to expected results Step 7 You may loop through this entire process more than once depending on the results of your analysis Follow the step by step process in the sections below to see how this is done 8 1 2 Step 1 Define Your Problem The first step in creating a UDF and using it in your ANSYS FLUENT model involves defining your model equation s Consider the elbow duct illustrated in Figure 8 1 1 The domain has a velocity inlet on the left side and a pressure outlet at the top of the right side Mesh FLUENT 12 0 2d pbns lam Figure 8 1 1 The Mesh for the Elbow Duct Example A flow field in which a constant x velocity is applied at the inlet will be compared with one where a parabolic x velocity profile is applied The results of a constant velocity of 0 1 m s at the inlet are shown in Figures 8 1 2 and 8 1 3 Release 12 0 ANSYS Inc January 26 2009 8 1 Step By Step UDF Example 1 41e 01 1 27e 01 1 12e 01 9 84e 02 8 44e 02
121. float_a double double_b float cmplx_r float cmplx_i tstcom_ DEF INE_ON_DEMAND fort_test float a 3 0 float_b double d b 1 5 int i c 2 Complex zZ QComplex qz d addab_ k amp a amp b amp c Message n nFortran code gives 4 f d f f n a c b d Message Common Block TSTCOM set to g hg d n tstcom_ float_a tstcom_ double_b tstcom_ int_c Message Common Complex Number is f fj n tstcom_ cmplx_r tstcom_ cmplx_i Message BLANK Common Block has an array of size 4d n BLNK__ size for i 0 i lt _BLNK__ size i Message array d g n i _BLNK__ array i float_b float b ccmplx_ amp z amp a amp float_b Message Function CCMPLX returns Complex Number Ag hgj n z r z i qcmplx_ amp qz amp a amp float_b Message Function QCMPLX returns Complex Number hg hgj n qz r qz i Release 12 0 ANSYS Inc January 26 2009 5 23 Compiling UDFs 3 The makefile is then modified to specify the UDF C source file test_use c and the external object file test o as shown below for re User modifiable section Hr rr rn SOURCES test_use c FLUENT_INC path ansys_inc v120 fluent Precompiled User Object files for example o files from f sources USER_OBJECTS test o Note that in the previous example path represents the directory where you installed ANSYS FLUENT 4 Finally the Makefile is executed by issuing the following com
122. form of communication between processes The most common mode of communication is between the host and the node processes 7 14 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs 7 5 2 Communicating Between the Host and Node Processes There are two sets of similar macros that can be used to send data between the host and the compute nodes host_to_node_type_num and node_to_host_type_num Host to Node Data Transfer To send data from the host process to all the node processes indirectly via compute node 0 we use macros of the form host_to_node_type_num val_1 val_2 val_num where num is the number of variables that will be passed in the argument list and type is the data type of the variables that will be passed The maximum number of variables that can be passed is 7 Arrays and strings can also be passed from host to nodes one at a time as shown in the examples below Examples integer and real variables passed from host to nodes host_to_node_int_1 count host_to_node_real_7 leni len2 widthi width2 breadthi breadth2 vol string and array variables passed from host to nodes char wall_name wall 17 int thread_ids 10 1 29 5 32 18 2 55 21 72 14 host_to_node_string wall_name 8 remember terminating NUL character host_to_node_int thread_ids 10 Note that these host_to_ node communication macros do not need to be protected by compiler direct
123. from the Mesh Motion UDF drop down list Click Create then Close See Section 2 6 4 DEFINE_GRID_MOTION for details about DEFINE_GRID_MOTION functions Release 12 0 ANSYS Inc January 26 2009 6 87 Hooking UDFs to ANSYS FLUENT 6 5 5 Hooking DEFINE_SDOF_PROPERTIES UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SDOF_PROPERTIES UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones dialog box in ANSYS FLUENT To hook the UDF to ANSYS FLUENT you will first need to select Transient from the Time list in the Solver group box of the General task page lt Tee Transient Next enable the Dynamic Mesh option in the Dynamic Mesh task page DnA Dynamic Mesh Then enable the Six DOF option in the Options group box and open the Dynamic Mesh Zones dialog box Figure 6 5 6 Dynamic Mesh Create Edit Select Rigid Body under Type in the Dynamic Mesh Zones dialog box Figure 6 5 6 and click the Motion Attributes tab Make sure that the On option in the Six DOF Solver Options group box is enabled and select the function name e g stage libudf from the Six DOF UDF drop down list Click Create then Close See Section 2 6 5 DEFINE SDOF_ PROPERTIES for details about DEFINE SDOF PROPERTIES functions 6 88 Release 12 0 ANSYS
124. graphical user interface dialog boxes in ANSYS FLUENT after the function has been interpreted or compiled The second set of input arguments to the DEFINE macro are variables that are passed into your function from the ANSYS FLUENT solver For example the macro DEFINE_PROFILE inlet_x_velocity thread index defines a boundary profile function named inlet_x_velocity with two variables thread and index that are passed into the function from ANSYS FLUENT These passed in variables are the boundary condition zone ID as a pointer to the thread and the index identifying the variable that is to be stored After the UDF has been interpreted or compiled its name e g inlet_x_velocity will become visible and selectable in drop down lists in the appropriate boundary condition dialog box e g Velocity Inlet in ANSYS FLUENT Fa Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error i Make sure that there are no spaces between the macro e g DEFINE_PROFILE and the first parenthesis of the arguments as this will cause an error in Windows i Do not include a DEFINE macro statement e g DEFINE PROFILE within a comment in your source code This will cause a compilation error Release 12 0 ANSYS Inc January 26 2009 1 4 Defining Your UDF Using DEFINE Macros 1 4 1 Including the udf h Header
125. graphics dialog box e g profile UDF for a material property you will either get a real time error message or when you go to initialize or iterate the solution ANSYS FLUENT will report an error in the dialog box Figure 6 7 1 Figure 6 7 1 The Error Dialog A message will also be reported to the console and log file Error get_udf_function function dpm_timestep libudf has wrong type 28 26 Error Object f Release 12 0 ANSYS Inc January 26 2009 6 95 Hooking UDFs to ANSYS FLUENT 6 96 Release 12 0 ANSYS Inc January 26 2009 Chapter 7 Parallel Considerations This chapter contains an overview of user defined functions UDFs for parallel ANSYS FLUENT and their usage Details about parallel UDF functionality can be found in the following sections e Section 7 1 Overview of Parallel ANSYS FLUENT e Section 7 2 Cells and Faces in a Partitioned Mesh e Section 7 3 Parallelizing Your Serial UDF e Section 7 4 Parallelization of Discrete Phase Model DPM UDFs e Section 7 5 Macros for Parallel UDFs e Section 7 6 Limitations of Parallel UDFs e Section 7 7 Process Identification e Section 7 8 Parallel UDF Example e Section 7 9 Writing Files in Parallel 7 1 Overview of Parallel ANSYS FLUENT ANSYS FLUENT s parallel solver computes a solution to a large problem by simultane ously using multiple processes that may be executed on the same machine or on different machines in a network It do
126. gt vv3 vv vv3 return vv 8 58 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples FUNCTION RKEOS_density Returns density given T and P double RKEOS_density double temp double press double yi return 1 RKEOS_spvol temp press Kg m3 FUNCTION RKEOS_dvdp Returns dv dp given T and rho double RKEOS_dvdp double temp double density double al a2 alp a2p a3p v press double afun a0 pow TCRIT temp NRK press RKEOS_pressure temp density v 1 density al cO rgas temp press a2 bb b0 rgas temp b0 press afun press alp rgas temp press press a2p alp b0 afun press press a3p afun bb press press return a3ptv a2ptv alp a2tv 2 a1 3 v Release 12 0 ANSYS Inc January 26 2009 8 59 Examples FUNCTION RKEOS_dvdt Returns dv dT given T and rho double RKEOS_dvdt double temp double density double al a2 dadt alt a2t a3t v press double afun a0 pow TCRIT temp NRK press RKEOS_pressure temp density v 1 density dadt NRK afun temp al cO rgas temp press a2 bb b0 rgas temp b0 pr
127. host node which writes it to the file This process is known as marshalling Thus file writing in parallel is done in the following stages 1 The host process opens the file 2 Compute node 0 sends its data to the host 3 The other compute nodes send their data to compute node 0 4 Compute node 0 receives the data from the other compute nodes and sends it to the host 5 The host receives the data sent from all the compute nodes and writes it to the file 6 The host closes the file Since the SERIAL HOST and NODE processes are performing different tasks the example below appears long and utilizes a large number of compiler directives If however as an exercise you make three copies of this example and in each copy delete the unused sections for either the SERIAL HOST or NODE versions then you will see that it is actually quite a simple routine Example Writing Data to a Common File on the Host Process s File System pE aaao ooo oo oo k kkk kk kkk kkk kkk kkk kkk This function will write pressures and positions for a fluid zone to a file on the host machine EEEE ooo oo k kkk kk kkk kkk include udf h define FLUID_ID 2 7 40 Release 12 0 ANSYS Inc January 26 2009 7 9 Writing Files in Parallel DEF INE_ON_DEMAND pressures_to_file Different variables are needed on different nodes if RP_HOST Domain domain Get_Domain 1 Thread thread cell_t c else int i endif if RP_
128. in the premixed combustion model see Chapter 17 Modeling Premixed Combustion in the separate User s Guide and the partially premixed combustion model see Chapter 18 Modeling Partially Premixed Combustion in the separate User s Guide Usage DEFINE _TURB_PREMIX SOURCE name c t turb flame _speed source Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the turbulent premixed source term is to be applied real turb_flame_speed Pointer to the turbulent flame speed real source Pointer to the reaction progress source term Function returns void There are five arguments to DEFINE_TURB_PREMIX_SOURCE name c t turb_flame_speed and source You supply name the name of the UDF c t turb_flame_speed and source are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the turbulent flame speed to the value referenced by the turb_flame_speed pointer It will also need to set the source term to the value refer enced by the source pointer Example The following UDF named turb_flame_src specifies a custom turbulent flame speed and source term in the premixed combustion model The source code must be executed as a compiled UDF in ANSYS FLUENT In the standard premixed combustion model in ANSYS FLUENT the mean reaction rate of the progress variable that is the source term is modeled as PSe PuUil Vel 2 3 11 2 1 22 R
129. include general 3D expressions in your code and the ND macros take care of removing the z components of a vector when you are compiling with RP_2D Release 12 0 ANSYS Inc January 26 2009 3 69 Additional Macros for Writing UDFs ND_ND The constant ND_ND is defined as 2 for RP_2D ANSYS FLUENT 2D and RP_3D ANSYS FLUENT 3D It can be used when you want to build a 2 x 2 matrix in 2D anda3 x 3 matrix in 3D When you use ND_ND your UDF will work for both 2D and 3D cases without requiring any modifications real A ND_ND ND_ND for i 0 i lt ND_ND i for j 0 j lt ND_ND j A i j fG j ND_SUM The utility ND_SUM computes the sum of ND_ND arguments ND_SUM x y z 2D x y 3D x y Z ND_SET The utility ND_LSET generates ND_ND assignment statements ND_SET u v w C_U c t C_V c t C_W c t u C_U c t v C_V c t if 3D 21 w C_W c t 3 70 Release 12 0 ANSYS Inc January 26 2009 3 4 Vector and Dimension Macros 3 4 3 The NV Macros The NV macros have the same purpose as ND macros but they operate on vectors i e arrays of length ND_ND instead of separate components NV_V The utility NV_V performs an operation on two vectors NV_V a x a 0 x 0 ali x 1 etc Note that if you use instead of in the above equation then you get a 0 x 0 etc See Section 2 6 4 DEFINE_GRID MOTION for an example UDF that utilizes NV_V NV_VV
130. is no analytical solution for the overall particle reaction rate It uses Brent s method to find the root of a function known to lie between x1 and z2 The root will be refined until its accuracy has reached tolerance tol This is demonstrated in Example 2 Auxiliary function zbrent_pr_rate real func real real int cxboolean char real ruser int iuser cxboolean buser char cuser real x1 real x2 real tol cxboolean ifail Auxiliary function returns real Example 1 The following UDF named user_pr_rate specifies a particle reaction rate given by Equation 7 3 9 in the separate Theory Guide where the effectiveness factor 1 is defined as Lf a Od where x is the fractional conversion of the particle char mass In this case the UDF will be applied to all surface particle reactions defined in the ANSYS FLUENT model UDF of specifying the surface reaction rate of a particle include udf h define A1 0 002 define El 7 9e7 DEFINE_PR_RATE user_pr_rate c t r mw pp p sf dif_i cat_i rr Argument types cell_t c Thread t Reaction r reaction structure real mw species molecular weight real pp gas partial pressures Tracked_Particle p particle structure real sf current mass fractions of solid species in particle char mass 2 60 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros int dif_i index of diffusion controlled species int cat_i index
131. k kkk kkk k kkk Example of an adjust UDF that uses Lookup_Thread Note that if this UDF is applied to a multiphase flow problem the thread that is returned is the mixture level thread BE AAR AAAI I I I I I KOKI AK AK AK CA A A A IKK KK aK A A A A A A A kK kkk kkk include udf h domain passed to Adjust function is mixture domain for multiphase DEFINE_ADJUST print_f_centroids domain real FC 2 face_t f int ID 1 Zone ID for wall 1 zone from Boundary Conditions task page Thread thread Lookup_Thread domain ID begin_f_loop f thread F_CENTROID FC f thread 3 30 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros printf x coord 7f y coord 7f FCO FC 1 end_f_loop f thread Zone ID THREAD_ID You can use THREAD_ID when you want to retrieve the integer zone ID number displayed in a boundary conditions dialog box such as Fluid that is associated with a given thread pointer t Note that this macro does the inverse of Lookup Thread see above int zone_ID THREAD_ID t Domain Pointer Get Domain You can use the Get_Domain macro to retrieve a domain pointer when it is not explicitly passed as an argument to your UDF This is commonly used in ON_DEMAND functions since DEFINE_ON_DEMAND is not passed any arguments from the ANSYS FLUENT solver It is also used in initialization and adjust functions for multiphase applications where a phase domain pointer is n
132. many topics and details that are not covered in this chapter including for example while and do while control statements unions recursion structures and reading and writing files If you are unfamiliar with C please consult a C language reference guide e g 6 9 before you begin the process of writing UDFs for your ANSYS FLUENT model Release 12 0 ANSYS Inc January 26 2009 A 1 C Programming Basics A 2 Commenting Your C Code It is good programming practice to document your C code with comments that are useful for explaining the purpose of the function In a single line of code your comments must begin with the identifier followed by text and end with the identifier as shown by the following This is how I put a comment in my C program Comments that span multiple lines are bracketed by the same identifiers This is how I put a comment in my C program that spans more than one line Do not include a DEFINE macro name e g DEFINE PROFILE within a comment in your source code This will cause a compilation error A 3 C Data Types in ANSYS FLUENT The UDF interpreter in ANSYS FLUENT supports the following standard C data types int integer number long integer number of increased range float floating point real number double double precision floating point real number char single byte of memory enough to hold a character Note that in ANSYS FLUENT real is a typedef that switches b
133. memory using C_UDMI The volume is then retrieved from user defined memory and used in the DEFINE_SOURCE UDF Release 12 0 ANSYS Inc January 26 2009 7 33 Parallel Considerations include udf h static real spark_center ND_ND 20e 3 1e 3 static int fluid_chamber_ID 2 DEFINE_ADJUST adjust domain real vol xc ND_ND dis ND_ND radius cell_t c Thread tc tc Lookup_Thread domain fluid_chamber_ID radius RP_Get_Real spark radius vol Q begin_c_loop_int c tc C_CENTROID xc c tc NV_VV dis xc spark_center if NV_MAG dis lt radius vol C_VOLUME c tc end_c_loop_int c tc vol PRF_GRSUM1 vol begin_c_loop_int c tc A C_UDMI c tc 1 vol end_c_loop_int c tc DEFINE_SOURCE energy_source c t dS eqn if RP_HOST real xc ND_ND dis ND_ND real source radius vol CA rpm start_CA rpm RP_Get_Real dynamesh in cyn crank rpm 7 34 Release 12 0 ANSYS Inc January 26 2009 7 7 Process Identification start_CA RP_Get_Real spark start ca CA rpm CURRENT_TIME 6 RP_Get_Real dynamesh in cyn crank start angle if CA gt start_CA amp amp CA lt start_CA RP_Get_Real spark duration rpm 6 i radius RP_Get_Real spark radius vol C_UDMI c t 1 C_CENTROID xc c t NV_VV dis xc spark_center if NV_MAG dis lt radius source RP_Get_Real spark ene
134. mesh time TIME_TO_ABSOLUTE_CRANK_ANGLE time Macro which takes the current time as input and returns the absolute value of the crank angle that is displayed on the mesh preview screen 2 214 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros Note that in_cyl_ca_period is the value entered for Crank Period in the In Cylinder Set tings dialog box which can be opened via the Dynamic Mesh task page The usage of this variable or the macros specified previously necessitates that the DEFINE_DYNAMIC_ZONE_PROPERTY UDF be a compiled UDF Their usage is illustrated in the example that follows Note that the header file dynamesh_tools h should be included in the UDF as shown in the example that follows Example UDF hook for implementing varying cell layering height Arguments are the Name of the UDF variable for dynamic thread and variable which holds the layering height value Works only as a compiled UDF because the usage of in_cyn_ca_period and the macros are not allowed in interpreted UDFs Header file dynamesh_tools h should be included in order to access the macros DYNAMESH_CURRENT_TIME and TIME_TO_ABSOLUTE_CRANK_ANGLE include udf h include dynamesh_tools h DEFINE_DYNAMIC_ZONE_PROPERTY nonconst_height dt 1h int temp Local variable for storing the value of Absolute Crank Angle real abs_ca Local variables for saving time and Crank Angle etc real half quar
135. not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 described in Section 3 2 6 Domain Pointer Get_Domain Note that the values for pt and cell threads are set within the looping function mp_thread_loop c is typically used along with begin_c_loop begin_c_loop loops over cells in a cell thread When begin_c_loop is nested within mp_thread_loop_c you can loop over all cells in all phase cell threads within a mixture Looping Over Phase Face Threads in Mixture mp_thread_loop_f The mp_thread_loop_f macro loops through all face threads at the mixture level within the mixture domain and provides the pointers of the phase level face threads associated with each mixture level thread This is nearly identical to the thread_loop_f macro when applied to the mixture domain The difference is that in addition to stepping through each face thread the macro also returns a pointer array pt that identifies the corresponding phase level threads The pointer to the face thread for the ith phase is ptLi where i is the phase domain_index pt i can be used as an argument to macros requiring the phase level thread pointer The phase domain index can be re trieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details Thread pt Thread face_threads Domain mixture_domain mp_thread_loop_f face_threads mixture_domain pt The
136. of ANSYS FLUENT supplied macros This can be significant if for example you want to introduce new data structures in your UDF A summary of the differences between interpreted and compiled UDFs is presented below See Chapters 4 and 5 for details on interpreting and compiling UDFs respectively in ANSYS FLUENT Interpreted UDF s are portable to other platforms can all be run as compiled UDFs do not require a C compiler are slower than compiled UDFs are restricted in the use of the C programming language cannot be linked to compiled system or user libraries can access data stored in an ANSYS FLUENT structure only using a predefined macro see Chapters 3 Release 12 0 ANSYS Inc January 26 2009 1 7 Overview e Compiled UDFs execute faster than interpreted UDFs are not restricted in the use of the C programming language can call functions written in other languages specifics are system and compiler dependent cannot necessarily be run as interpreted UDFs if they contain certain elements of the C language that the interpreter cannot handle In summary when deciding which type of UDF to use for your ANSYS FLUENT model e use interpreted UDFs for small straightforward functions e use compiled UDFs for complex functions that have a significant CPU requirement e g a property UDF that is called on a per cell basis every iteration require a
137. of catalyst species real rr rate of reaction kg s real ash_mass P_INIT_MASS p 1 DPM_CHAR_FRACTION p DPM_VOLATILE_FRACTION p real one_minus_conv MAX O P_MASS p ash_mass P_INIT_MASS p DPM_CHAR_FRACTION p real rate Ai exp E1 UNIVERSAL_GAS_CONSTANT P_T p rr rate P_DIAM p P_DIAM p M_PI sf 0 one_minus_conv Example 2 The following compiled UDF named user_rate specifies a particle reaction rate given by Equation 7 3 4 to Equation 7 3 7 in the separate Theory Guide The reaction order on the kinetic rate is 0 9 and the effectiveness factor 7 is defined as el eee where zx is the fractional conversion of the particle char mass In this case it is necessary to obtain a numerical solution for the overall surface reaction rate This UDF is called only for reaction 2 which means that the default ANSYS FLUENT solution will be used for the rest of the particle surface reactions defined UDF of specifying the surface reaction rate of a particle using a numerical solution include udf h define c1 5e 12 define A1 0 002 define E1 7 9e7 define tolerance 1e 4 define order 0 9 real reaction_rate real rate real ruser int iuser cxboolean buser char cuser Release 12 0 ANSYS Inc January 26 2009 2 61 DEFINE Macros Note that all arguments in the reaction_rate function call in your c source file MUST be on the same line or a compilation error
138. of face_t freturned by C_FACE Release 12 0 ANSYS Inc January 26 2009 Additional Macros for Writing UDFs Flow Variable Macros for Cells You can access flow variables using macros listed in Table 3 2 8 Table 3 2 8 Macros for Cell Flow Variables Defined in mem h Macro Argument Types Returns CR c t cell_t c Thread t density CP c t cell_t c Thread t pressure CU c t cell t c Thread t u velocity C_V c t cell t c Thread t v velocity C_W c t cell_t c Thread t w velocity C_T c t cell_t c Thread t temperature CH c t cell_t c Thread t enthalpy CK c t cell t c Thread t turb kinetic energy C_NUT Coe cell t c Thread t turbulent viscosity for Spalart Allmaras CD c t cell_t c Thread t turb kinetic energy dissipation rate C_O c t cell t c Thread t specific dissipation rate C YI c t i cell_t c Thread t int i species mass fraction note int i is species index Gradient G and Reconstruction Gradient RG Vector Macros You can access gradient and reconstruction gradient vectors and components for many of the cell variables listed in Table 3 2 8 ANSYS FLUENT calculates the gradient of flow in a cell based on the divergence theory and stores this value in the variable identified by the suffix G For example cell temperature is stored in the variable C_T and the temperature gradient of the cell is stored in C_T_G The gradients stored in variables with the
139. only if the particle does not cross a cell boundary Table 3 2 28 Macros for Particle Cell Index and Thread Pointer Defined in dpm h Name Arguments Argument Types Returns P_CELL p P_CELL_THREAD p Tracked Particle p Tracked_Particle p cell index of the cell that the particle is currently in pointer to the thread of the cell that the particle is currently in Release 12 0 ANSYS Inc January 26 2009 3 37 Additional Macros for Writing UDFs Table 3 2 29 Macros for Particles at Injection into Domain Defined in dpm h Macro Argument Types Returns P_INIT_POS p i P_INIT_VEL p i P_INIT_DIAM p P_INIT_TEMP p P_INIT_RHO p P_INIT_MASS p P_INIT_LF p Tracked_Particle Tracked_Particle Tracked_Particle p Tracked Particle p Tracked Particle p Tracked_Particle p Tracked_Particle p p int i p int i position i 0 1 2 velocity i 0 1 2 diameter temperature density mass liquid fraction wet combusting particles only Table 3 2 30 Macros for Particle Species Laws and User Scalars Defined in dpm h Macro Argument Types Returns P_EVAP_SPECIES_INDEX p P_DEVOL_SPECIES_INDEX p P_OXID_SPECIES_INDEX p P_PROD_SPECIES_INDEX p P_CURRENT_LAW p P_NEXT_LAW p P_USER_REAL p i Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle
140. phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEF INE_MASS_TRANSFER DEF INE_HET_RXN_RATE phase interaction phase interaction phase interaction phase interaction phase interaction Release 12 0 ANSYS Inc January 26 2009 C 15 Quick Reference Guide for Multiphase DEFINE Macros C 16 Release 12 0 ANSYS Inc January 26 2009 Bibliography R H Aungier A Fast Accurate Real Gas Equation of State for Fluid Dynamic Analysis Applications Journal of Fluids Engineering 117 277 281 1995 N P Cheremisinoff Fluid Flow Pocket Handbook Gulf Publishing Co Houston TX 1984 A M Douaud and P Eyzat Four Octane Number Method for Predicting the Anti Knock Behavior of Fuels in Engines SAE Transactions 780080 1978 E R G Eckert and R M Drake Analysis of Heat and Mass Transfer McGraw Hill Co 1972 S Jendoubi H S Lee and T K Kim Discrete Ordinates Solutions for Radiatively Participating Media in a Cylindrical Enclosure J Thermophys Heat Transfer 7 2 213 219 1993 B Kernighan and D Ritchie The C Programming Language Prentice Hall second edition 1988 J C Livengood and P C
141. procedure for setting up the folder structure described in Section Sec tion 5 3 1 Set Up the Directory Structure 2 Copy your precompiled object files e g myobject1 obj myobject2 obj to all of the architecture version folders you created in Step 1 e g ntx86 2d ntx86 3d i The object files should be compiled using similar flags to those used by ANSYS FLUENT e g c Za 3 Using a text editor edit the user_nt udf files in each architecture version folder 5 18 Release 12 0 ANSYS Inc January 26 2009 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources UNIX and Linux Systems 1 Follow the procedure for setting up the directory structure described in Section 5 3 1 Set Up the Directory Structure 2 Copy your precompiled object files e g myobject1 o myobject2 0 to all of the architecture version directories you created in Step 1 e g ultra 2d and ultra 3d i The object files should be compiled using similar flags to those used for ANSYS FLUENT Common flags used by ANSYS FLUENT are KPIC 0 and ansi which often have equivalents such as fpic 03 and xansi 3 Using a text editor edit the file makefile in your src directory to set the following three parameters SOURCES FLUENT_INC and USER_OBJECTS SOURCES Put the names of your UDF C files here They will be calling the functions in the User Objects FLUENT_INC the path to your release directory USER_OBJECTS the precompi
142. real 2 70 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros There are three arguments to DEFINE_PRANDTL_T_WALL name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the thermal wall function Prandtl number to the solver Example DORR k k k kk kk k k k k k k k k k A A k k k K k AK kk I I k I K K I kK a a 2k Kk 2k 2k K 2k 2k K 2k K K Specifying a constant thermal wall function Prandtl number BECO CRRA kkk kk kkk kk include udf h DEFINE_PRANDTL_T_WALL user_pr_t_wall c t real pr_t_wall pr_t_wall 0 85 return pr_t_wall Hooking a Prandtl Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PRANDTL_T_WALL is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_t_wal1 will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 14 Hooking DEFINE_PRANDTL UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 71 DEFINE Macros 2 3 15 DEFINE PROFILE Description You can use DEFINE_PROFILE to define a custom boundary profile that varies as a function of spatial coordinates or time Some of the variables you can customize at a boundary are e velocity
143. s You can remove a selection by clicking the path in Source File s list and then clicking the Remove button Click OK when your selections are complete The Select File dialog box will close and the file you selected e g udfexample c will appear in the Source Files list in the Compiled UDFs dialog box Figure 5 2 3 You can delete a file after adding it by selecting the source file and then clicking Delete in the Compiled UDFs dialog box 5 6 Release 12 0 ANSYS Inc January 26 2009 5 2 Compiling a UDF Using the GUI Select File O mywork My Recent Documents kot on LEBKTHOMP My Network Files of type Source Files 3 crs Source File s Z mywork udfexample c B B Remove Figure 5 2 2 The Select File Dialog Box Compiled UDFs Source Files _ Header Files Library Name libudf Figure 5 2 3 The Compiled UDFs Dialog Box Release 12 0 ANSYS Inc January 26 2009 Compiling UDFs 7 In the Compiled UDFs dialog box select additional header files that you want to include in the compilation by clicking Add under Header File s and repeat the previous step In the Compiled UDFs dialog box Figure 5 2 3 enter the name of the shared library you want to build in the Library Name field or leave the default name libudf and click Build All of the UDFs that are contained within each C source file you selected will be compil
144. scalars allocated Fill first UDS with temperature raised to fourth power thread_loop_c t domain if NULL THREAD_STORAGE t SV_UDS_I T4 begin_c_loop c t real T C_T c t C_UDSI c t T4 pow T 4 end_c_loop c t thread_loop_f t domain if NULL THREAD_STORAGE t SV_UDS_I T4 begin_f_loop f t real T 0 if NULL THREAD_STORAGE t SV_T Release 12 0 ANSYS Inc January 26 2009 8 41 Examples T F_T f t else if NULL THREAD_STORAGE t gt t0 SV_T T C_T F_CO f t t gt t0 F_UDSI f t T4 pow T 4 end_f_loop f t Fill second UDS with magnitude of gradient thread_loop_c t domain x if NULL THREAD_STORAGE t SV_UDS_I T4 amp amp NULL T_STORAGE_R_NV t SV_UDSI_G T4 begin_c_loop c t C_UDSI c t MAG_GRAD_T4 NV_MAG C_UDSI_G c t T4 end_c_loop c t thread_loop_f t domain if NULL THREAD_STORAGE t SV_UDS_I T4 amp amp NULL T_STORAGE_R_NV t gt t0 SV_UDSI_G T4 begin_f_loop f t F_UDSI f t MAG_GRAD_T4 C_UDSI F_CO f t t gt t0 MAG_GRAD_T4 end_f_loop f t The conditional statement if NULL THREAD_STORAGE t SV_UDS_I T4 is used to check if the storage for the user defined scalar with index T4 has been allocated while NULL T_STORAGE_R_NV t SV_UDSI_G T4 checks whether the storage of the gradient of the user defined scalar with index T4 has been allocated 8 42
145. selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 27 Hooking DEFINE_VR_RATE UDFs for details 2 1 32 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 28 DEFINE_WALL_FUNCTIONS Description You can use DEFINE_WALL_FUNCTIONS to provide custom wall functions for applications when you want to replace the standard wall functions in ANSYS FLUENT Note that this is available only for use with the k e turbulence models Usage DEFINE WALL _FUNCTIONS name f t c0 t0 wf_ret yPlus Emod Argument Type Description symbol name UDF name face_t f face index Thread t pointer to cell thread cell_t cO cell index Thread t0O pointer to face thread int wf_ret wall function index real yPlus y value real Emod wall function E constant Function returns real There are eight arguments to DEFINE_WALL_FUNCTIONS name f t c0 t0 wf_ret yPlus and Emod You supply name the name of the UDF f t cO tO wf_ret yPlus and Emod are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the real value of the wall functions U dU and dY for laminar and turbulent regions and return them to the solver Example The following UDF named user_log_law computes U and dU and dY for laminar and turbulent regions using DEFINE_WALL_FUNCTIONS The source code can be interpreted or compiled in ANSYS FLUENT Release 12 0 ANS
146. session executes from a user defined Scheme routine executes when a UDF library is loaded executes after a case file is read executes after a data file is read initializes variables executes asynchronously reads writes variables to case and data files DEFINE_ADJUST DEFINE_DELTAT DEF INE_EXECUTE_AT_END DEF INE_EXECUTE_AT_EXIT DEFINE EXECUTE FROM GUI DEF INE_EXECUTE_ON_LOADING DEFINE _EXECUTE_AFTER_CASE DEF INE_EXECUTE_AFTER_DATA DEFINE_INIT DEFINE ON DEMAND DEFINE_RW_FILE User Defined Function Hooks Adaptive Time Step Settings User Defined Function Hooks User Defined Function Hooks N A N A N A N A User Defined Function Hooks Execute On Demand User Defined Function Hooks Release 12 0 ANSYS Inc January 26 2009 DEFINE Macros 2 2 1 DEFINE_ADJUST Description DEFINE_ADJUST is a general purpose macro that can be used to adjust or modify AN SYS FLUENT variables that are not passed as arguments For example you can use DEFINE_ADJUST to modify flow variables e g velocities pressure and compute inte grals You can also use it to integrate a scalar quantity over a domain and adjust a boundary condition based on the result A function that is defined using DEFINE_ADJUST executes at every iteration and is called at the beginning of every iteration before trans port equations are solved For an overview of the ANSYS FLUENT solution process which shows when a DEFINE_AD
147. sih_s yil7 site fraction of sih_s T_w F_T f t rho_w C_R c0 t0 C_T c0 t0 T_w sih4 rho_w mw 0 converting of mass fractions to molar concentrations si2h6 rho_w mw 1 sih2 rho_w mw 2 h2 x rho_w mw 3 ar x rho_w mw 4 si_s site_rho converting of site fractions to site concentrations sih_s site_rho if STREQ r gt name reaction 1 rr 100 0 sih4 else if STREQ r gt name reaction 2 rr 0 1 sih_s else if STREQ r gt name reaction 3 rr 100 si2h6 si_s Release 12 0 ANSYS Inc January 26 2009 2 1 17 DEFINE Macros else if STREQ r gt name reaction 4 rr 1 0e10 sih2 Hooking a Surface Reaction Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SR_RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my_rate will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 22 Hooking DEFINE_SR_RATE UDFs for details 2 3 23 DEFINE_TRANS UDFs The following DEFINE macros can be used to specify transition correlations for the Tran sition SST model in ANSYS FLUENT DEF INE_TRANS_FLENGTH Description You can use DEFINE_TRANS_FLENGTH to specify the transition length for the Transition SST turbulence model Usage DEFINE _TRANS_F
148. solved The indices are EQ_NO for NO EQ_HCN for HCN EQ_N20 for NjO and EQ_NH3 for NH3 e MOLECON Pollut SPE returns the molar concentration of a species specified by SPE which is either the name of the species or IDX i when the species is a pollutant like NO SPE must be replaced by one of the following identifiers FUEL 02 0 OH H20 N2 N CH CH2 CH3 IDX NO IDX N20 IDX HCN IDX NH3 For example for O gt molar concentration you should call MOLECON Pollut 02 whereas for NO molar concentration the call should be MOLECON Pollut IDX NO The identifier FUEL represents the fuel species as specified in the Fuel Species drop down list under Prompt NO Parameters in the NOx Model dialog box e ARRH Pollut K returns the Arrhenius rate calculated from the constants specified by K K is defined using the Rate_Const data type and has three elements A B and C The Arrhenius rate is given in the form of R ATP exp C T where T is the temperature Note that the units of K must be in m gmol J s e POLLUT_CTMAX Pollut_Par can be used to modify the Tmax value used as the upper limit for the integration of the temperature PDF when temperature is accounted for in the turbulence interaction modeling You must make sure not to put this macro under any conditions within the UDF e g IN PDF or OUT_PDF SO Macros The following macros can be used in SO model UDFs in the calculation of pollutant rates These macros are
149. subdomain Get_Domain 2 returns phase with ID 2 domain pointer and assigns to variable Example The following example is a UDF named get_coords that prints the thread face centroids for two specified thread IDs The function implements the Get_Domain utility for a single phase application In this example the function Print_Thread_Face_Centroids uses the Lookup_Thread function to determine the pointer to a thread and then writes the face centroids of all the faces in a specified thread to a file The Get_Domain 1 function call returns the pointer to the domain or mixture domain in the case of a multiphase application This argument is not passed to DEFINE_ON_DEMAND 3 32 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros DOR OR 3K FK OK 2K K FK FK 2K A 2K 2K K FK 2K K FK FK 2K K FK 2K 2k K 2k 2K 2k K 2k Example of UDF for single phase that uses Get_Domain utility EEEE E ooo I I KOK AK AK AEA k kkk kk k kkk include udf h FILE fout void Print_Thread_Face_Centroids Domain domain int id real FC 2 face_t f Thread t Lookup_Thread domain id fprintf fout thread id d n id begin_f_loop f t F_CENTROID FC f t fprintf fout fyd Ye fe g n f FC 0 FC 1 FC 2 end_f_loop f t fprintf fout n DEFINE_ON_DEMAND get_coords Domain domain domain Get_Domain 1 fout fopen faces out w Print_Thread_Face_Centroids domain 2
150. substitution directive given by define RAD 1 2345 will cause the preprocessor to replace all instances of the variable RAD in your UDF with the number 1 2345 There may be many references to the variable RAD in your function but you only have to define it once in the macro directive the preprocessor does the work of performing the substitution throughout your code In another example define AREA_RECTANGLE X Y X Y all of the references to AREA RECTANGLE X Y in you UDF are replaced by the product of X and Y File Inclusion Directive Using include When you use the include file inclusion directive the C preprocessor replaces the line include filename with the contents of the named file include filename The file you name must reside in your current folder The only exception to this rule is the udf h file which is read automatically by the ANSYS FLUENT solver For example the file inclusion directive given by include udf h will cause the udf h file to be included with your source code Release 12 0 ANSYS Inc January 26 2009 A 17 C Programming Basics The ANSYS FLUENT solver automatically reads the udf h file from the following folder path ANSYS Inc v120 fluent fluent12 0 2 src udf h where path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and z is replaced by the appropriate number for the release e g 9 for fluent12 0 9 A 15
151. that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_T name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the temperature Prandtl number to the solver Release 12 0 ANSYS Inc January 26 2009 2 69 DEFINE Macros Example Specifying a Constant Temperature Prandtl Number include udf h DEFINE_PRANDTL_T user_pr_t c t real pr_t pr_t 0 85 return pr_t J Hooking a Prandtl Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PRANDTL_T is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_t will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 14 Hooking DEFINE_PRANDTL UDFs for details DEFINE_PRANDTL_T_WALL Description You can use DEFINE PRANDTL_T WALL to specify Prandtl numbers for thermal wall func tions Usage DEFINE_PRANDTL_T_WALL name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns
152. the UDF e g IN PDF or OUT_PDF Dynamic Mesh Macros The macros listed in Table 3 2 34 are useful in dynamic mesh UDFs The argument dt is a pointer to the dynamic thread structure and time is a real value These macros are defined in the dynamesh_tools h Table 3 2 34 Macros for Dynamic Mesh Variables Defined in dynamesh_tools h Name Arguments Argument Types Returns DT_THREAD dt Dynamic_Thread dt pointer to a thread DT_CG dt Dynamic_Thread dt center of gravity vector DT_VEL_CG dt Dynamic_Thread dt cg velocity vector DT_OMEGA CG t Dynamic Thread dt angular velocity vector DT_THETA dt Dynamic Thread dt orientation of body fixed DYNAMESH_CURRENT_TIME TIME TO ABSOLUTE CRANK _ANGLE time N A real time axis vector current dynamic mesh time absolute value of the crank angle See Section 2 6 4 DEFINE_GRID MOTION for an example UDF that utilizes DT_THREAD Release 12 0 ANSYS Inc January 26 2009 3 43 Additional Macros for Writing UDFs 3 2 8 User Defined Scalar UDS Transport Equation Macros This section contains macros that you can use when defining scalar transport UDFs in ANSYS FLUENT Note that if you try to use the macros listed below e g F_UDSI C_UDSI before you have specified user defined scalars in your ANSYS FLUENT model in the User Defined Scalars dialog box then an error will result Set User Scalar Name ANSYS FLUENT assigns a default name f
153. the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Six DOF UDF drop down list in the Dynamic Mesh Zones dialog box in ANSYS FLUENT See Section 6 5 5 Hooking DEFINE_SDOF_PROPERTIES UDF s for details on how to hook your DEFINE_SDOF_PROPERTIES UDF to ANSYS FLUENT 2 224 Release 12 0 ANSYS Inc January 26 2009 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros This section provides information on how you can define UDFs that can be used in UDS transport equations in ANSYS FLUENT See Section 9 1 User Defined Scalar UDS Transport Equations in the separate User s Guide for UDS equation theory and details on how to setup scalar equations Descriptions of DEFINE macros for UDS applications are provided below Definitions of DEFINE macros are contained in the udf h header file For your convenience they are also listed in Appendix B Detailed examples of user defined scalar transport UDFs can be found in Section 8 2 5 User Defined Scalars Section 2 7 1 Introduction Section 2 7 2 DEFINE_ANISOTROPIC_DIFFUSIVITY Section 2 7 3 DEFINE_UDS_FLUX Section 2 7 4 DEFINE UDS UNSTEADY 2 7 1 Introduction For each of the N scalar equations you specified in your ANSYS FLUENT model you can supply a unique UDF for the diffusion coefficients flux and unsteady terms in the scalar transport equation For multipha
154. thread i Some UDFs such as DEFINE_ON_DEMAND functions are not passed any pointers to data structures while others are not passed the pointer the UDF needs If your UDF needs to access a thread or domain pointer that is not directly passed by the solver through an argument then you will need to use a special ANSYS FLUENT supplied macro to obtain the pointer in your UDF For example DEFINE_ADJUST is passed only the domain pointer so if your UDF needs a thread pointer it will have to declare the variable locally and then obtain it using the special macro Lookup_Thread An exception to this is if your UDF needs a thread pointer to loop over all of the cell threads or all the face threads in a domain using thread_c_loop c t or thread _f_loop f t respectively and it is not passed to the DEFINE macro Since the UDF will be looping over all threads in the domain you will not need to use Lookup_Thread to get the thread pointer to pass it to the looping macro you ll just need to declare the thread pointer and cell or face ID locally before calling the loop See Section 2 2 1 DEFINE_ADJUST for an example As another example if you are using DEFINE_ON DEMAND which is not passed any pointer argument to execute an asynchronous UDF and your UDF needs a domain pointer then the function will need to declare the domain variable locally and obtain it us ing Get_Domain See Section 2 2 9 DEFINE_ON_DEMAND for an example Refer to Sec tion 3 2 6
155. to enable the Dynamic Mesh option in the Dynamic Mesh task page DANE Dynamic Mesh Next open the Dynamic Mesh Zones dialog box Release 12 0 ANSYS Inc January 26 2009 6 81 Hooking UDFs to ANSYS FLUENT OANA Create Edit Dynamic Mesh Zones Zone Names Dynamic Mesh Zones axis move w Fluid move seat valve Type O Stationary Rigid Body O Deforming O User Defined Motion Attributes Geometry Definition Meshing Options Motion UDF Profile i piston libudF v Center of Gravity Location Center of Gravity Orientation x m Theta_zZ deg D0 oi J Coen en Coste Coos Cre Figure 6 5 1 The Dynamic Mesh Zones Dialog Box Select Rigid Body under Type in the Dynamic Mesh Zones dialog box Figure 6 5 1 and click the Motion Attributes tab Finally select the function name e g piston libudf from the Motion UDF Profile drop down list and click Create then Close See Section 2 6 1 DEFINE_CG_MOTION for details about DEFINE_CG_MOTION functions 6 5 2 Hooking DEFINE_DYNAMIC_ZONE_PROPERTY UDFs The DEFINE_DYNAMIC_ZONE_PROPERTY UDF can be hooked in order to define the following e the swirl center for in cylinder applications e a variable cell layering height Hooking a Swirl Center UDF After you have complied your DEFINE_DYNAMIC_ZONE_PROPERTY UDF as described in Chapter 5 Compiling UDFs the name of the function you supp
156. ts Time step Function returns real There are three arguments to DEFINE_DPM_TIMESTEP name p and ts You supply the name of your user defined function p and ts are variables that are passed by the ANSYS FLUENT solver to your UDF Your function will return the real value of the DPM particle timestep to the solver Example 1 The following compiled UDF named limit_to_e_minus_four sets the time step to a maximum value of le 4 If the time step computed by ANSYS FLUENT and passed as an argument is smaller than le 4 then ANSYS FLUENT s time step is returned 2 202 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros Time step control UDF for DPM include udf h include dpm h DEFINE_DPM_TIMESTEP limit_to_e_minus_four p dt if dt gt 1 e 4 p gt next_time_step 1 e 4 return 1 e 4 return dt Example 2 The following compiled UDF named limit_to_fifth_of_prt computes the particle re laxation time based on the formula 24 d18u 2 5 2 Tp fracpp p Op Res where d y Cell 2 5 3 H The particle time step is limited to a fifth of the particle relaxation time If the particle time step computed by ANSYS FLUENT and passed as an argument is smaller than this value then ANSYS FLUENT s time step is returned Particle time step control UDF for DPM include udf h include dpm h DEFINE_DPM_TIMESTEP limit_to_fifth_o
157. udf h define pi 4 atan 1 define diam2 3 e 4 DEFINE_EXCHANGE_PROPERTY custom_drag cell mix_thread s_col f_col Thread thread_g thread_s real x_vel_g x_vel_s y_vel_g y_vel_s abs_v slip_x slip_y rho_g rho_s mu_g reyp afac bfac void_g vfac fdrgs taup k_g_s find the threads for the gas primary and solids secondary phases THREAD_SUB_THREAD mix_thread s_col gas phase THREAD_SUB_THREAD mix_thread f_col solid phase thread_g thread_s find phase velocities and properties x_vel_g C_U cell thread_g y_vel_g C_V cell thread_g x_vel_s C_U cell thread_s Release 12 0 ANSYS Inc January 26 2009 2 1 41 DEFINE Macros y_vel_s C_V cell thread_s slip_x x_vel_g x_vel_s slip_y y_vel_g y_vel_s C_R cell thread_g C_R cell thread_s rho_g rho_s mu_g C_MU_L cell thread_g compute slip abs_v sqrt slip_x slip_x slip_y slip_y compute Reynold s number reyp rho_g abs_v diam2 mu_g compute particle relaxation time taup rho_s diam2 diam2 18 mu_g void_g C_VOF cell thread_g gas vol fracx compute drag and return drag coeff k_g_s afac pow void_g 4 14 if void_g lt 0 85 bfac 0 281632 pow void_g 1 28 else bfac pow void_g 9 076960 vfac 0 5 afac 0 06 reyptsqrt 0 0036 reyp reypt0 12 reyp 2 bfac afac afac afac fdrgs void_g pow 0 63 sqrt rey
158. used to calculate the pressure This value is then assigned to F_PROFILE which uses the integer i passed to it by the solver based on your selection of the UDF as the boundary condition for pressure in the Pressure Inlet dialog box to set the pressure face value in memory Example 2 Velocity Turbulent Kinetic Energy and Turbulent Dissipation Rate Profiles In the following example DEFINE_PROFILE is used to generate profiles for the x velocity turbulent kinetic energy and dissipation rate respectively for a 2D fully developed duct flow Three separate UDFs named x_velocity k profile and dissip profile are defined These functions are concatenated in a single C source file and can be interpreted or compiled in ANSYS FLUENT The 1 7th power law is used to specify the x velocity component Ug UeF CM x Ux free 5 A fully developed profile occurs when 6 is one half the duct height In this example the mean x velocity is prescribed and the peak free stream velocity is determined by averaging across the channel The turbulent kinetic energy is assumed to vary linearly from a near wall value of to a free stream value of king 0 002u2 The dissipation rate is given by C A k3 where the mixing length is the minimum of y and 0 0850 is the von Karman constant 0 41 Release 12 0 ANSYS Inc January 26 2009 2 75 DEFINE Macros The friction velocity and wall shear take the forms Ur T
159. used to flag the code that total internal reflection has occurred real specular_reflectivity Specular reflectivity for the given direction s real specular_ transmissivity Specular transmissivity for the given direction s Function returns void There are eleven arguments to DEFINE_DOM_SPECULAR_REFLECTIVITY name f t nband na nb ray_ direction en internal reflection specular reflectivity and specular transmissivity You supply name the name of the UDF f t nband n_a n_b ray_direction en internal_reflection specular_reflectivity and specular_transmissivity are variables that are passed by the ANSYS FLUENT solver to your UDF Example In the following UDF named user_dom_spec_ref1 specular reflectivity and transmis sivity values are altered for a given ray direction s at face f Fa Note that in the example that follows the DEFINE_DOM_SPECULAR_REFLECTIVITY statement is broken up into three lines for the sake of readability In your source file you must make sure that the DEFINE statement is on one line only 2 40 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros UDF to alter the specular reflectivity and transmissivity at semi transparent walls along direction s at face f include udf h DEFINE_DOM_SPECULAR_REFLECTIVITY user_dom_spec_refl f t nband n_a n_b ray_direction en internal_reflection specular_reflectivity specular_transmissivity real angle cos_thet
160. user defined mixing law UDF for a mixture material you will need to use special utilities to access species material properties These are described below If you want to define a custom mass diffusivity property when modeling species transport you must use DEFINE_DIFFUSIVITY instead of DEFINE PROPERTY See Section 2 3 3 DEFINE DIFFUSIVITY for details on DEFINE_DIFFUSIVITY UDFs For an overview of the ANSYS FLUENT solution process which shows when a DEFINE_PROPERTY UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Some of the properties you can customize using DEFINE PROPERTY are e density as a function of temperature e viscosity e thermal conductivity e absorption and scattering coefficients e laminar flow speed e rate of strain e user defined mixing laws for density viscosity and thermal conductivity of mixture materials e partially premixed unburnt properties for unburnt density unburnt temperature unburnt specific heat and unburnt thermal diffusivity If you would like to use a UDF to define specific heat proper ties you must use the DEFINE SPECIFIC HEAT as described in Sec tion 2 3 21 DEFINE_SPECIFIC_HEAT i Note that when you specify a user defined density function for a com pressible liquid flow application you must also include a speed of sound function in your model Compressible liquid density UDFs can be used in the pressure based solver and for single phase multiphase mixture and cavitation models
161. user_cphi libudf from the drop down list for Mixing Model Constant Cphi and click OK See Section 2 3 2 DEFINE_CPHI for details about defining DEFINE CPHI functions Release 12 0 ANSYS Inc January 26 2009 6 15 Hooking UDFs to ANSYS FLUENT 6 2 3 Hooking DEFINE DIFFUSIVITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DIFFUSIVITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first open the Materials task page e BVP lecae lS Make a selection in the Materials list and click the Create Edit button to open the appropriate Create Edit Materials dialog box Figure 6 2 3 Create Edit Materials Name Order Materials by mixture template Material Type mixture v Name Chemical Formula Chemical Formula FLUENT Mixture Materials s mixture template v FLUENT Database User Defined Database Properties Thermal Conductivity w m k r 0 0454 Viscosity kg m s constant 1 72e 05 Mass Diffusivity m2 s a defined mean_age_diff libudF v Figure 6 2 3 The Create Edit Materials Dialog Box You then have the following options e To hook a mass diffusivity UDF for the species transport equations select user defined from the Mass Diffusivity dr
162. variable arguments to mp_thread_loop_f are face_threads mixture_domain and pt face_threads is a pointer to the face threads and mixture_domain is a pointer to the mixture level domain pt is an array pointer whose elements contain pointers to phase level threads Release 12 0 ANSYS Inc January 26 2009 3 63 Additional Macros for Writing UDFs mixture_domain is automatically passed to your UDF by the ANSYS FLUENT solver if you are using a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and your UDF is hooked to the mixture If mixture_domain is not explicitly passed to your UDF you may use another utility macro to retrieve it e g Get_Domain 1 de scribed in Section 3 2 6 Domain Pointer Get_Domain Note that the values for pt and face_threads are set within the looping function mp_thread_loop f is typically used along with begin _f_loop begin_f_loop loops over faces in a face thread When begin f_loop is nested within mp_thread_loop f you can loop over all faces in all phase face threads within a mixture 3 3 2 Advanced Multiphase Macros For most standard UDFs written for multiphase models e g source term material property profile functions variables that your function needs domain pointers thread pointers etc are passed directly to your UDF as arguments by the solver in the solution process All you need to do is hook the UDF to your model and everything is taken care of For examp
163. will first need to open the Cell Zone Conditions task page gt EEA Select the appropriate zone in the Zone selection list of the Cell Zone Conditions task page and click the Edit button to open the cell zone condition dialog box e g the Fluid dialog box as shown in Figure 6 2 26 6 42 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs Zone Name fluid Material Name water C Porous Zone C Laminar Zone Source Terms C Fixed values Motion Porous Zone Reaction Source Terms Fixed values Mass kalm3 s 2 sources x Momentum n m3 mo j Momentum n m3 osouces Z Momentum njm3 osouces Figure 6 2 26 The Fluid Dialog Box Next enable the Source Terms option in the cell zone condition dialog box and click the Source Terms tab This will display the source term parameters mass momentum etc in the scrollable window Click the Edit button next to the source term e g Mass you wish to customize in order to open the appropriate source term dialog box e g the Mass sources dialog box as shown in Figure 6 2 27 Specify the number of terms you wish to model by setting the Number of Mass Sources text entry box e g 2 and then select the function name e g usr_mass_src1 libudf and usr_mass_src2 libudf from the appropriate drop down list Note that the UDF name that is displayed in the drop down lists is preceded by the word udf Clic
164. with default names User Memory 0 and User Memory 1 will be defined for your model and the default variable names will appear in postprocessing dialog boxes You can change the default names if you wish using Set User Memory Name as described below Set_User_Memory_Name The default name that appears in the graphical user interface and on plots for user defined memory UDM values in ANSYS FLUENT e g User Memory 0 can now be changed using the function Set User Memory Name void Set_User_Memory_Name int i char name i is the index of the memory value and name is a string containing the name you wish to assign It is defined in sg_udms h The Set User Memory Name function should be used only once and is best used in an EXECUTE_ON_LOADING UDF see Section 2 2 6 DEFINE_EXECUTE_ON_LOADING Due to the mechanism used User Memory values cannot be renamed after they have been set so if the name is changed in a UDF for example and the UDF library is reloaded then the old name could remain In this case restart ANSYS FLUENT and load the library again Release 12 0 ANSYS Inc January 26 2009 3 47 Additional Macros for Writing UDFs F_UDMI You can use F_UDMI Table 3 2 37 to access or store the value of the user defined memory on a face F_UDMI can be used to allocate up to 500 memory locations in order to store and retrieve the values of face field variables computed by UDFs These stored values can then be used for postproc
165. write will be written as a single file for the serial parallel host and parallel node versions but different parts of the function will be compiled to generate different versions of the dynamically linked shared object file libudf so libudf d11 on Windows Print tasks for example may be assigned exclusively to the host while a task such as computing the total volume of a complete mesh will be assigned to the compute nodes Since most operations are executed by the serial solver and either the host or compute nodes negated forms of compiler directives are more commonly used Note that the primary purpose of the host is to interpret commands from Cortex and to pass those commands and data to compute node 0 for distribution Since the host does not contain mesh data you will need to be careful not to include the host in any calculations that could for example result in a division by zero In this case you will need to direct the compiler to ignore the host when it is performing mesh related calculations by wrapping those operations around the if RP_HOST directive For example suppose that your UDF will compute the total area of a face thread and then use that total area to compute a flux If you do not exclude the host from these operations the total area on the host will be zero and a floating point exception will occur when the function attempts to divide by zero to obtain the flux Example if RP_HOST avg_pres total_pres_a to
166. your DEFINE_EXECUTE_AT_EXIT UDF it is ready to be hooked to ANSYS FLUENT Note that you can hook multiple at exit UDFs to your model if desired To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 1 6 Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking General Purpose UDFs Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Figure 6 1 6 The User Defined Function Hooks Dialog Box Click the Edit button next to Execute At Exit to open the Execute At Exit Functions dialog box Figure 6 1 7 Select the function s you wish to hook to your model from the Available Execute At End Functions list Click Add and then OK to close the dialog box The name of the function you selected will be displayed in the Execute At Exit field of the User Defined Function Hooks dialog box If you select more than one function the number will be displayed e g 2 selected Click OK in the User Defined Function Hooks dialog box to apply the settings See Section 2 2 4 DEFINE_EXECUTE_AT_EXIT for details about defining DEFINE_EXECUTE_AT_EXIT functions Release 12 0 ANSYS Inc January 26 2009 6 7 Hooking UDFs to ANSYS FLUENT Execute at Exit Functions
167. 0 6 80e 00 6 40e 00 6 00e 00 5 60e 00 5 20e 00 4 80e 00 4 40e 00 4 00e 00 3 60e 00 3 20e 00 2 80e 00 2 40e 00 2 00e 00 1 60e 00 1 20e 00 8 00e 01 4 00e 01 0 00e 00 Contours of Stream Function kg s FLUENT 12 0 2d pbns lam pbns lam Figure 8 2 22 Stream Function Contours Suggesting Solidification 8 2 4 Reaction Rates This section contains an example of a custom reaction rate UDF It is executed as a compiled UDF in ANSYS FLUENT Volume Reaction Rate A custom volume reaction rate for a simple system of two gaseous species is considered The species are named species a and species b The reaction rate is one that converts species a into species b at a rate given by the following expression K Xa 2T O 8 2 4 R TEKAT eea where X is the mass fraction of species a and K and K are constants The 2D planar domain consists of a 90 degree bend The duct has a porous region covers the bottom and right hand wall and the reaction takes place in the porous region only The species in the duct have identical properties The density is 1 0 kg m and the viscosity is 1 7894x10 kg m s Release 12 0 ANSYS Inc January 26 2009 8 35 Examples The outline of the domain is shown in Figure 8 2 23 The porous medium is the region below and to the right of the line that extends from the inlet on the left to the pressure outlet at the top of the domain Mesh FLUENT 12 0 2d pbn
168. 0 the number of faces is passed from all of the compute nodes to compute node 0 using the message passing macro PRF_CSEND_INT See Section 7 5 8 Message Passing Macros for details on PRF_CSEND_INT Example Usage of myid int noface 0 begin_f_loop f tf loops over faces in a face thread and computes number of faces noface end_f_loop f tf Pass the number of faces from node 1 2 to node 0 if RP_NODE if myid node_zero PRF_CSEND_INT node_zero amp noface 1 myid endif 7 36 Release 12 0 ANSYS Inc January 26 2009 7 8 Parallel UDF Example 7 8 Parallel UDF Example The following is an example of a serial UDF that has been parallelized so that it can run on any version of ANSYS FLUENT host node serial Explanations for the various changes from the simple serial version are provided in the comments and discussed below The UDF named face_av is defined using an adjust function computes a global sum of pressure on a specific face zone and computes its area average Example Global Summation of Pressure on a Face Zone and its Area Average Computation include udf h DEFINE_ADJUST face_av domain Variables used by serial host node versions int surface_thread_id 0 real total_area 0 0 real total_force 0 0 Parallelized Sections if RP_HOST Compile this section for computing processes only serial and node since these variables are not avail
169. 2 31 hooking to ANSYS FLUENT 6 13 DEFINE_CPHI UDFs defining 2 33 hooking to ANSYS FLUENT 6 15 DEFINE_DELTAT UDFs defining 2 7 hooking to ANSYS FLUENT 6 3 DEFINE_DIFFUSIVITY UDFs defining 2 34 example 8 45 hooking to ANSYS FLUENT 6 16 Index 3 Index DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs defining 2 36 hooking to ANSYS FLUENT 6 19 DEF INE_DOM_SOURCE UDFs defining 2 38 hooking to ANSYS FLUENT 6 20 DEF INE_DOM_SPECULAR_REFLECTIVITY UDFs defining 2 39 hooking to ANSYS FLUENT 6 21 DEFINE_DPM_BC UDFs defining 2 156 hooking to ANSYS FLUENT 6 63 DEFINE_DPM_BODY_FORCE UDFs defining 2 163 hooking to ANSYS FLUENT 6 65 DEFINE_DPM_DRAG UDFs defining 2 165 hooking to ANSYS FLUENT 6 66 DEFINE_DPM_EROSION UDFs defining 2 167 hooking to ANSYS FLUENT 6 67 DEFINE_DPM_HEAT MASS UDFs defining 2 173 hooking to ANSYS FLUENT 6 68 DEFINE_DPM_INJECTION_INIT UDFs defining 2 177 hooking to ANSYS FLUENT 6 69 DEFINE_DPM_LAW UDFs defining 2 181 hooking to ANSYS FLUENT 6 71 DEFINE DPM OUTPUT UDFs defining 2 183 hooking to ANSYS FLUENT 6 72 DEFINE DPM PROPERTY UDFs defining 2 186 hooking to ANSYS FLUENT 6 73 DEFINE DPM SCALAR UPDATE UDF s defining 2 189 hooking to ANSYS FLUENT 6 75 DEFINE DPM SOURCE UDFs defining 2 193 hooking to ANSYS FLUENT 6 76 Index 4 DEF INE_DPM_SPRAY_COLLIDE UDF s defining 2 194 hooking to ANSYS FLUENT 6 77 DEFINE_DPM_SWITCH UDF defining 2 196 hoo
170. 21 Hooking UDFs to ANSYS FLUENT 6 2 7 Hooking DEFINE EMISSIVITY WEIGHTING FACTOR UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_EMISSIVITY_WEIGHTING_FACTOR UDF the name of the func tion you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 9 in ANSYS FLUENT In the Radiation Model dialog box Discrete Ordinates DO must be selected from the Model list and a nonzero value must be entered for Number of Bands in the Non Gray Model group box To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 9 Define User Defined gt Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux i Chemistry Step DO Source DO Diffuse Reflectivity DO Specular Reflectivity DO Emissivity Weighting Factor Ha a wg Figure 6 2 9 The User Defined Function Hooks Dialog Box Select the function name e g em_wt libudf in the DO Emissivity Weighting Factor drop down list in the User Defined Function Hooks dialog box and click OK 6 22 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs See Section 2 3 7 DEFINE_EMISSIVI
171. 2k 2 2k 2 2k PK kkk k kak ak ak kak 2k OOO 2K 2K K FK 2K 2K K 3K 2K K FK 3K 2K K FK 2K 2K 2K IR I AK RK FK KK 2k 2 2k 2k KKK 2k PK k k k kk k k OO 2K k 3K 2K K K 2k KK RR I A RK kK 2k 2 2k 2k KKK 2k Message0 n MessageO Gradients pee Na S MessageO n if NNULLP THREAD_STORAGE t SV_P_G Message0 show grad Gradient of P is available n if NNULLP THREAD_STORAGE t SV_U_G Message0 show grad Gradient of U is available n if NNULLP THREAD_STORAGE t SV_V_G Message0 show grad Gradient of V is available n J if NNULLP THREAD_STORAGE t SV_W_G ae Message0 show grad Gradient of W is available n if NNULLP THREAD_STORAGE t SV_T_G Message0 show grad Gradient of T is available n if NNULLP THREAD_STORAGE t SV_H_G Release 12 0 ANSYS Inc January 26 2009 3 13 Additional Macros for Writing UDFs Message0 show grad Gradient if NNULLP THREAD_STORAGE t Message0 show grad Gradient if NNULLP THREAD_STORAGE t Message0 show grad Gradient if NNULLP THREAD_STORAGE t Message0 show grad Gradient if NNULLP THREAD_STORAGE t Message0 show grad Gradient if nspe int ns 0 spe_loop ns nspm of H is SV_K_G of K is SV_D_G of D is SV_O_G of 0 is SV_NUT_G available n available n available n available
172. 33 CC4 0 25 CC5 T_REF usersMessage messagefunc usersError errorfunc usersMessage nLoading Redlich Kwong Library s n filename FUNCTION RKEOS_pressure Returns density given T and density double RKEOS_pressure double temp double density double v 1 density double afun a0 pow TCRIT temp NRK return rgas temp v bb afun v v b0 Release 12 0 ANSYS Inc January 26 2009 8 57 Examples FUNCTION RKEOS_spvol Returns specific volume given T and P double RKEOS_spvol double temp double press double ai a2 a3 double vv vvi vv2 vv3 double qq qq3 sqq rr tt dd double afun a0 pow TCRIT temp NRK al cO rgas temp press a2 bb b0 rgas temp b0 press afun press a3 afun bb press Solve cubic equation for specific volume qq al xai 3 a2 9 rr 2 al al ai 9 al a2 27 a3 54 qq3 qq qq qq dd qq3 rr rr If dd lt 0 then we have one real root If dd gt 0 then we have three roots gt choose largest root if dd lt 0 4 tt sqrt dd pow fabs rr 0 333333 vv tt qq tt al 3 else tt acos rr sqrt qq3 sqq sqrt qq vvi 2 sqq cos tt 3 al 3 vv2 2 sqq cos tt 2 PI 3 al1 3 vv3 2 sqq xcos tt 4 PI 3 al1 3 vv vv1 gt vv2 vv1 vv2 vv vv
173. 40 N2 mi 2 31 99880 02 mi 3 44 00995 CO2 return mi i double Cp_i double T double r int i double cpil20 cpil0 2014 00 H20 cpil1 1040 67 N2 cpil2 919 31 02 cpil3 840 37 C0O2 return cpilil ig double K_i double T double r int i double ki 20 Release 12 0 ANSYS Inc January 26 2009 8 73 Examples kil0 0 02610 H20 ki 1 0 02420 N2 ki 2 0 02460 02 ki 3 0 01450 CO2 return kili double Mu_i double T double r int i double mui 20 muilO 1 340F 05 H20 mui 1 1 663E 05 N2 mui 2 1 919F 05 02 mui 3 1 370E 05 C02 return mui i double Rgas_i double T double r int i double Rgasi Rgasi UNIVERSAL_GAS_CONSTANT Mw_i i return Rgasi double Gm_i double T double r int i double gammai gammai Cp_i T r i Cp_i T r i Rgas_i T r i return gammai DOR OO k kk k I a a aK kkk k kkk kkk 8 74 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Mixture Functions Structure DOR GR RAR RR a 22k 5 3k 2k 2k a 2k 2k 2k ok 2k 2k 2 ak 2k 2k 2 ak ak UDF_EXPORT RGAS_Functions RealGasFunctionList MIXTURE_Setup initialize MIXTURE_density density MIXTURE_enthalpy enthalpy MIXTURE_entropy entropy MIXTURE_specific_heat specific_heat MIXTURE _mv mole
174. 5 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 15 Release 12 0 ANSYS Inc January 26 2009 6 29 Hooking UDFs to ANSYS FLUENT Define gt User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Volume Reaction Rate nan Particle Reaction Rate user_pr_rate libudf Figure 6 2 15 The User Defined Function Hooks Dialog Box i You must enable the particle surface reactions option before you can hook the UDF by selecting Volumetric and Particle Surface under Reactions in the Species Model dialog box Select the function name e g user_pr_rate libudf in the Particle Reaction Rate Function drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 13 DEFINE_PR_RATE for details about defining DEFINE_PR_RATE functions 6 30 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 14 Hooking DEFINE_PRANDTL UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_PRANDTL UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model
175. 6 A 6 User Defined Data Types 2 sd 4 eae Rw Oe ee we Ke A 7 Dee BOI oe ee ee eee oe ee oS ee ee A 7 AS Functions s pw pd GO we eu ae ed Bees HK He A 7 Pad AN er 6 oR amp SEAS EBHEAS EDR SAE ASA HEED REO a A 8 AdO PG cscs A oh Re Be ea RL ow a a SEO A 8 A 11 Control Statements 22 2 gawk eek RO RR Dek Ra hee ee ee G A 10 AJLI if Statement eai SALE KOR EEE CHE DE SEEDS A 10 A112 if else Statement kn Oe ew ee Ree wo A 10 Aio DOC LOODS ae 4 oe Gh ee Sh Oe ee ee ey GSS A 11 A12 Common C Operators sc c te G4 ie Hee eH eee HR HE oO A 12 A 12 1 Arithmetic p rators o c sod rera redat REG nwa A 12 AT22 Logical Operators ser ea eo OS RW Oe CR ORS A 12 Release 12 0 ANSYS Inc January 26 2009 CONTENTS Paka Gr Ley TOR es besa owe ye ee ER RS Kw RES A 13 1 Trigonometric Functions 14 64 4 2i4 ewan A 13 2 Miscellaneous Mathematical Functions A 133 Standard I O F ncti ns e lt s nak sa nk oa aed A 14 Preprocessor Directives o oo 00002 eee A 15 Comparison with FORTRAN 4 B DEFINE Macro Definitions B 1 General Solver DEFINE Macros aoaaa aa a B 2 Model Specific DEFINE Macro Definitions B 3 Multiphase DEFINE Macros lt lt lt 5 a B 4 Dynamic Mesh Model DEFINE Macros B 5 Discrete Phase Model DEFINE Macros B 6 User Defined Scalar UDS DEFINE Macros C Quick Reference Guide for Multiphase DEFINE Macros Col VOF Mod
176. 7 37 7 40 RP_NODE 7 12 7 13 7 40 RP_THREAD 2 195 2 197 Run Calculation task page 8 20 sample problems 8 13 Sample Trajectories dialog box 6 72 sampling plane output 2 183 scalar transport equation UDFs anisotropic diffusivity 2 227 examples 8 40 flux term 2 230 unsteady term 2 234 scalar transport UDFs diffusion coefficient 2 225 Release 12 0 ANSYS Inc January 26 2009 Index fixed value boundary condition 2 226 flux 2 226 source term example 8 25 source terms 2 226 unsteady 2 226 wall inflow and outflow boundary conditions 2 227 scalar update UDFs 2 189 scattering phase UDFs 2 95 Scheme command 3 77 interpreter 3 77 variables 3 77 modifying 3 78 Schmidt number UDFs 2 124 Select File dialog box 5 6 8 10 sg_mem h header file 3 20 shared library 1 2 building 5 5 showgrad c 3 10 SI units 1 2 six degrees of freedom solver property UDFs 2 221 slip velocity UDFs 2 151 2 152 solar intensity UDFs 2 98 Solid dialog box 6 43 solidification 8 30 solution process 1 12 density based solver 1 12 pressure based solver 1 12 solver data access using macros 3 1 solver variables accessing 3 1 source files 1 2 4 1 source term UDF s discrete ordinates model 2 38 DPM 2 193 example 8 25 for ANSYS FLUENT transport equations 2 100 ignition model 2 47 premixed combustion model 2 122 source terms 1 3 Release 12 0 ANSYS Inc January 26 2009 SOx macros 3 41 SOx M
177. 8 examples beam direction profile 2 82 examples porosity function 2 83 Index 7 Index examples porous resistance direction vector 2 84 examples UDF 8 1 compiled only 2 61 2 66 2 115 2 117 9 122 2 130 2 157 2 159 2 164 2 166 2 168 2 177 2 187 2 190 2 197 9 009 S911 0 916 S918 2 219 2 232 8 40 interpreted or compiled 2 5 2 9 2 18 2 90 2 99 0 95 274 9 75 281 2 86 2 95 2 101 2 103 2 126 2 133 2 182 2 235 examples viscous resistance profile 2 83 exchange macros parallel 7 33 exchange property UDFs 2 139 EXCHANGE SVAR FACE MESSAGE 7 33 EXCHANGE_SVAR_MESSAGE 7 33 execute after reading case UDFs 2 16 execute after reading data UDFs 2 16 execute from GUI UDFs 2 11 Execute On Demand dialog box 6 10 execute on loading UDFs 2 13 execute at end UDFs 2 8 execute at exit UDFs 2 10 exterior cell looping macro parallel 7 23 F_LAREA 2 115 2 117 2 168 2 177 2 210 2 232 3 23 7 9 7 37 F_CO 2 115 2 117 2 168 2 232 3 26 F_C1 2 232 3 26 F_CENTROID 2 74 2 75 2 79 2 156 3 22 3 30 3 33 3 34 8 16 F_D 3 24 F_FLUX 2 232 3 24 F_H 3 24 F_K 3 24 F_NNODES 3 5 F_NODE 2 219 3 60 f_node_loop 2 219 3 59 F_P 3 24 F_PART 7 28 F_PROFILE 2 73 2 75 2 79 3 34 8 16 F_R 3 24 F_STORAGE_R 2 167 Index 8 FT 2117 34 EU 2232 3 04 F_UDMI 2 168 3 48 6 13 FV 2 299 5 24 FW 2 232 3 24 FYI 3 24 face 1 10 face area
178. 89e 02 2 89e 02 2 88e 02 2 88e 02 2 87e 02 2 87e 02 2 86e 02 2 86e 02 2 85e 02 2 85e 02 2 84e 02 2 84e 02 2 83e 02 2 83e 02 2 82e 02 2 82e 02 2 81e 02 2 81e 02 2 80e 02 Contours of Static Temperature k FLUENT 12 0 2d pbns lam Figure 8 2 15 Temperature Contours Illustrating Liquid Metal Cooling 1 716 03 1 626 03 1 54e 03 1 45e 03 1 36e 03 1 28e 03 1 19e 03 1 11e 03 1 02e 03 9 38e 04 8 53e 04 7 686 04 6 82e 04 5 97e 04 5 12e 04 4 266 04 3 41e 04 2 566 04 1 71e 04 8 53e 05 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 16 Velocity Magnitude Contours Suggesting Solidification Release 12 0 ANSYS Inc January 26 2009 8 29 Examples The solidification is further illustrated by line contours of stream function Figure 8 2 17 8 00e 00 7 60e 00 7 20e 00 6 80e 00 6 40e 00 6 00e 00 5 60e 00 5 20e 00 4 80e 00 4 40e 00 4 00e 00 3 60e 00 3 20e 00 2 80e 00 2 40e 00 2 00e 00 1 60e 00 1 20e 00 8 00e 01 4 00e 01 0 00e 00 Contours of Stream Function kg s FLUENT 12 0 2d pbns lam Figure 8 2 17 Stream Function Contours Suggesting Solidification To more accurately predict the freezing of a liquid in this manner an energy source term would be needed as would a more accurate value for the constant appearing in Equation 8 2 1 8 2 3 Physical Properties This section contains an applica
179. 9 2 173 DEFINE Macros POR kkk kk kkk kkk kkk kk kk kkk kk 4 4 k UDF for defining the heat and mass transport for multicomponent particle vaporization EEEE ooo ooo o kkk kk kkk kkk kkk include udf h DEFINE_DPM_HEAT_MASS multivap p Cp hgas hvap cvap_surf Z dydt dzdt int ns Material sp real dens_total 0 0 total vapor density real P_total 0 0 vapor pressure int nc TP_N_COMPONENTS p number of particle components Thread tO P_CELL_THREAD p thread where the particle is in Material gas_mix THREAD_MATERIAL DPM_THREAD tO p gas mixture material Material cond_mix P_MATERIAL p particle mixture material cphase_state_t c amp p gt cphase cell information of particle location real molwt MAX_SPE_EQNS molecular weight of gas species real Tp P_T p particle temperature real mp P_MASS p particle mass real molwt_bulk 0 average molecular weight in bulk gas real Dp DPM_DIAM_FROM_VOL mp P_RHO p particle diameter real Ap DPM_AREA Dp particle surface real Pr c gt sHeat c gt mu c gt tCond Prandtl number real Nu 2 0 0 6 sqrt p gt Re pow Pr 1 3 Nusselt number real h Nu c gt tCond Dp Heat transfer coefficient real dh_dt h c gt temp Tp Ap heat source term dydt 0 dh_dt mp Cp dzdt gt energy dh_dt mixture_species_loop ga
180. AD thread to_index m_lg 0 if C_T cell liq gt T_SAT m_lg 0 1 C_VOF cell liq C_R cell 1liq fabs C_T cell 1ligq T_SAT T_SAT J if m_lg 0 amp amp C_T cell gas lt T_SAT m_lg 0 1 C_VOF cell gas C_R cell gas fabs T_SAT C_T cell gas T_SAT return m_lg 2 1 50 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros Hooking a Mass Transfer UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_MASS_TRANSFER is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g liq_gas_source will become visible and selectable under Mass Transfer when you select the Mass tab op tion in the Phase Interaction dialog box and specify the Number of Mass Transfer Functions See Section 6 3 4 Hooking DEFINE_MASS_TRANSFER UDFs for details 2 4 5 DEFINE_VECTOR_EXCHANGE_PROPERTY Description You can use DEFINE VECTOR EXCHANGE PROPERTY to specify custom slip velocities for the multiphase Mixture model Usage DEFINE VECTOR EXCHANGE PROPERTY name c mixture thread second_column_phase_index first_column_phase_index vector_result Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description sym
181. ADOW t Do things here using the shadow wall thread ts Release 12 0 ANSYS Inc January 26 2009 3 35 Additional Macros for Writing UDFs 3 2 7 Model Specific Macros DPM Macros The macros listed in Tables 3 2 26 3 2 31 can be used to return real variables associated with the Discrete Phase Model DPM in SI units They are typically used in DPM UDFs that are described in Section 2 5 Discrete Phase Model DPM DEFINE Macros The variables are available in both the pressure based and the density based solver The macros are defined in the dpm h header file which is included in udf h The variable p indicates a pointer to the Tracked Particle structure Tracked Particle p which gives you the value for the particle at the current position Refer to the following sections for examples of UDFs that utilize some of these macros Section 260 DEF INE_DPM_LAW Section 25 1 DEFINE_DPM_BC Section 2 5 6 DEFINE_DPM_INJECTION_INIT Section 2 5 13 DEFINE_DPM_SWITCH and Sec tion 2 5 9 DEFINE DPM PROPERTY Table 3 2 26 Macros for Particles at Current Position Defined in dpm h Macro Argument Types Returns P_POS p i Tracked_Particle p int i position i 0 1 2 P_VEL p i Tracked Particle p int i velocity i 0 1 2 P_DIAM p Tracked Particle p diameter P_T p Tracked_Particle p temperature P_RHO p Tracked_Particle p density P_MASS p Tracked_Particle p mass P_TIME p Tracked Particle p current
182. AD_MATERIAL t sp real yi_h2o 0 mw_h2o0 1 0 real r_mix 0 0 if MATERIAL_TYPE m MATERIAL_MIXTURE mixture_species_loop m sp i r_mix C_YI c t i MATERIAL_PROP sp PROP_mwi if 0 strcmp MIXTURE_SPECIE_NAME m i h2o 2 1 98 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 0 strcmp MIXTURE_SPECIE_NAME m i H20 yi_h2o C_YI c t i mw_h2o MATERIAL_PROP sp PROP_mwi return ABS_P C_P c t op_pres yi_h2o mw_h2o r_mix H20_Saturation_Pressure C_T c t define CONDENS 1 0e 4 DEFINE_DPM_LAW condenshumidlaw p coupled real area real mp_dot cell_t c P_CELL p Get Cell and Thread from Thread t P_CELL_THREAD p Particle Structure using new macros area 4 0 M_PI P_DIAM p P_DIAM p Note This law only used if Humidity gt 1 0 so mp_dot always positive mp_dot CONDENS sqrt area myHumidity c t 1 0 if mp_dot gt 0 0 P_MASS p P_MASS p mp_dot P_DT p P_DIAM p pow 6 0 P_MASS p P_RHO p M_PI 1 3 P_T p C_T c t Assume condensing particle is in thermal equilibrium with fluid in cell define macro that is not yet standard define C_DPMS_ENERGY c t C_STORAGE_R c t SV_DPMS_ENERGY DEFINE_DPM_SOURCE dpm_source c t S strength p real mp_dot Release 12 0 ANSYS Inc January 26 2009 2 1 99 DEFINE Macros Material sp P_MATERIAL p m
183. AIN_SUB_DOMAIN int phase_domain_index 0 primary phase index is 0 Thread mixture_thread mixture level thread pointer Thread subthread THREAD_SUB_THREAD mixture_thread phase_domain_index mixture_thread is a pointer to a mixture level thread It is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a variable thread argument e g DEFINE_PROFILE and the function is hooked to the mixture Otherwise if the mixture thread pointer is not explicitly passed to your UDF then you will need to use the Lookup_Thread utility macro to retrieve it see Section 3 2 6 Thread Pointer for Zone ID Lookup_Thread phase_domain_index is an index of subdomain pointers It is an integer that starts with O for the primary phase and is incremented by one for each secondary phase phase domain index is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a phase domain index argument DEFINE_EXCHANGE_ PROPERTY DEFINE_VECTOR_EXCHANGE_PROPERTY and your UDF is hooked to a specific interaction phase See Section 2 4 2 DEFINE_EXCHANGE_PROPERTY for an example UDF Otherwise you will need to hard code the integer value of phase domain index to the THREAD SUB THREAD macro If your multiphase model has only two phases defined then phase_domain_index is 0 for the primary phase and 1 for the secondary phase However if you have more than one seconda
184. ANSYS FLUENT 12 0 UDF Manual April 2009 Copyright 2009 by ANSYS Inc All Rights Reserved No part of this document may be reproduced or otherwise used in any form without express written permission from ANSYS Inc Airpak Mechanical APDL Workbench AUTODYN CFX FIDAP FloWizard FLUENT GAMBIT Iceboard Icechip Icemax Icepak Icepro Icewave MixSim POLYFLOW TGrid and any and all ANSYS Inc brand product service and feature names logos and slogans are registered trademarks or trademarks of ANSYS Inc or its subsidiaries located in the United States or other countries All other brand product service and feature names or trademarks are the property of their respective owners CATIA V5 is a registered trademark of Dassault Systemes CHEMKIN is a registered trademark of Reaction Design Inc Portions of this program include material copyrighted by PathScale Corporation 2003 2004 ANSYS Inc is certified to ISO 9001 2008 See the on line documentation for the complete Legal Notices for ANSYS proprietary software and third party software If you are unable to access the Legal Notice contact ANSYS Inc Contents Preface i 1 Overview 1 1 1 1 What is a User Defined Function UDF 1 1 t2 Why Use UDES 222624 gadeg 444448446404 44 REGEES 1 3 Le Limitations BS oe ee ee Ree RES RE Se Ce 1 3 1 4 Defining Your UDF Using DEFINE Macros 1 4 1 4 1 Including the udf h Header File in Your Sourc
185. AO ooo o o kkk 21 kkk kkk 2k 2k 2k include udf h DEFINE_INIT my_init_func d cell_t c Thread t real xc ND_ND loop over all cell threads in the domain thread_loop_c t d loop over all cells begin_c_loop_all c t C_CENTROID xc c t if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 C_T c t 400 else C_T c t 300 end_c_loop_all c t J Release 12 0 ANSYS Inc January 26 2009 3 3 Additional Macros for Writing UDFs 3 2 Data Access Macros The macros presented in this section access ANSYS FLUENT data that you can utilize in your UDF Unless indicated these macros can be used in UDFs for single phase and multiphase applications e Section 3 2 1 Axisymmetric Considerations for Data Access Macros e Section 3 2 2 Node Macros e Section 3 2 3 Cell Macros e Section 3 2 4 Face Macros e Section 3 2 5 Connectivity Macros e Section 3 2 6 Special Macros e Section 3 2 7 Model Specific Macros e Section 3 2 8 User Defined Scalar UDS Transport Equation Macros e Section 3 2 9 User Defined Memory UDM Macros 3 2 1 Axisymmetric Considerations for Data Access Macros C side calculations for axisymmetric models in ANSYS FLUENT are made on a 1 radian basis Therefore when you are utilizing certain data access macros e g F_AREA or F_FLUX for axisymmetric flows your UDF will need to multiply the result by 2 PI utilizing the macr
186. Argument Types Usage C_UDMI c t i cell_t c Thread t int i stores the cell value of a user defined memory with index i There are three arguments to C_UDMI c thread and i c is the cell identifier thread is a pointer to the cell thread and i is an integer index that identifies the memory location where data is to be stored An index i of 0 corresponds to user defined memory location 0 or User Memory 0 Example UDF that Utilizes UDM and UDS Variables UDMs are often used to store diagnostic values derived from calculated values of a UDS Below is an example that shows a technique for plotting the gradient of any flow variable In this case the volume fraction of a phase is loaded into a user scalar If an iteration is made such that the UDS is not calculated the gradients of the scalar will nevertheless be updated without altering the values of the user scalar The gradient is then available to be copied into a User Memory variable for displaying include udf h define domain_ID 2 DEFINE_ADJUST adjust_gradient domain Thread t cell_t c face_t f domain Get_Domain domain_ID Fill UDS with the variable thread_loop_c t domain Release 12 0 ANSYS Inc January 26 2009 3 49 Additional Macros for Writing UDFs begin_c_loop c t C_UDSI c t 0 C_VOF c t J end_c_loop c t thread_loop_f t domain a if THREAD_STORAGE t SV_UDS_1I 0 NULL begin_f_loop f
187. Arrhenius reaction rate prod 1 for i 0 i lt r gt n_reactants i ci C_R c t yk r gt reactant i wk r gt reactant i prod pow ci r gt exp_reactant i xrate r gt A exp r gt E UNIVERSAL_GAS_CONSTANT C_T c t pow C_T c t r gt b prod xrr_t rate No return value 2 1 30 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 2 When multiple reactions are specified a volume reaction rate UDF is called several times in each cell Different values are assigned to the pointer r depending on which reaction the UDF is being called for Therefore you will need to determine which reaction is being called and return the correct rates for that reaction Reactions can be identified by their name through the r gt name statement To test whether a given reaction has the name reaction 1 for example you can use the following C construct if strcmp r gt name reaction 1 r gt name is identical to reaction 1 i Note that strcmp r gt name reaction 1 returns 0 which is equal to FALSE when the two strings are identical It should be noted that DEFINE _VR_RATE defines only the reaction rate for a predefined stoichiometric equation set in the Reactions dialog box thus providing an alternative to the Arrhenius rate model DEFINE_VR_RATE does not directly address the particular rate of species creation or depletio
188. Available Execute at Exit Functions 5 amp Selected Execute at Exit Functions B execute_at_exit1 libudf execute_at_exit2 libudf Remove Figure 6 1 7 The Execute At Exit Functions Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking General Purpose UDFs 6 1 5 Hooking DEFINE_INIT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_INIT UDF it is ready to be hooked to ANSYS FLUENT Note that you can hook multiple initialization UDFs to your model if desired To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 1 8 Define User Defined gt Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data mor Execute at Exit Wall Heat Flux Figure 6 1 8 The User Defined Function Hooks Dialog Box Click the Edit button next to Initialization to open the Initialization Functions dialog box Figure 6 1 9 Release 12 0 ANSYS Inc January 26 2009 6 9 Hooking UDFs to ANSYS FLUENT Initialization Functions Available Initialization Functions E B Selected Initialization Functions E amp my _init_Func2 libudF tmy_init_Func1 libudF Figure 6 1 9 The Initialization Functions Dialog Box Select the funct
189. C_P c t p_operating dp p p_ref rho rho_ref 1 0 dp BMODULUS return rho DEFINE_PROPERTY sound_speed c t real a real p dp p_operating p_operating RP_Get_Real operating pressure p C_P c t p_operating dp p p_ref a 1 dp BMODULUS sqrt BMODULUS rho_ref return a Hooking a Property UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PROPERTY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g sound_speed will become visible and selectable in dialog boxes in ANSYS FLUENT See Section 6 2 16 Hooking DEFINE PROPERTY UDFs for details 2 94 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 17 DEFINE_SCAT_PHASE_FUNC Description You can use DEFINE SCAT PHASE FUNC to specify the radiation scattering phase function for the discrete ordinates DO model The function computes two values the fraction of radiation energy scattered from direction 7 to direction j and the forward scattering factor Usage DEF INE_SCAT_ PHASE FUNC name cosine f Argument Type Description symbol name UDF name real cosine Cosine of the angle between directions 7 and j real f Pointer to the location in memory where the real forward scattering factor is stored Function returns real There are three arguments to DEFINE_SCA
190. Cell index Thread t Pointer to cell thread on which the anisotropic diffusivity function is to be applied int i Index that identifies the user defined scalar real dmatrix ND ND ND ND Anisotropic diffusivity matrix to be filled in by user Function returns void There are five arguments to DEFINE ANISOTROPIC DIFFUSIVITY name c t i and dmatrix You will supply name the name of the UDF c t i and dmatrix are variables that are passed by the ANSYS FLUENT solver to your UDF Your function will compute the diffusivity tensor for a single cell and fill dmatrix with it Note that anisotropic diffusivity UDFs are called by ANSYS FLUENT from within a loop on cell threads Con sequently your UDF will not need to loop over cells in a thread since ANSYS FLUENT is doing it outside of the function call Release 12 0 ANSYS Inc January 26 2009 2 227 DEFINE Macros Example The following UDF named cyl_ortho_diff computes the anisotropic diffusivity matrix for a cylindrical shell which has different diffusivities in radial tangential and axial directions This function can be executed as a compiled UDF paaa k kkk kkk kkk kk kkk kkk kk kk kkk kk kk kk kk Example UDF that demonstrates DEFINE_ANISOTROPIC_DIFFUSIVITY BOC COA o kkk k kkk kkk 24 24 kk include udf h Computation of anisotropic diffusivity matrix for cylindrical orthotropic diffusivity axis definition for cylindrical diffusivity static cons
191. Comparison with FORTRAN Many simple C functions are similar to FORTRAN function subroutines as shown in the example below A simple C function An equivalent FORTRAN function int myfunction int x INTEGER FUNCTION MYFUNCTION X int x y Z INTEGER X Y Z y 11 Y 11 Z xty Z X Y printf z d z WRITE 100 Z return Z MYFUNCTION Z END A 18 Release 12 0 ANSYS Inc January 26 2009 Appendix B DEFINE Macro Definitions B 1 General Solver DEFINE Macros The following definitions for general solver DEFINE macros see Section 2 2 General Pur pose DEFINE Macros are taken from the udf h header file define DEFINE_ADJUST mame domain void name Domain domain define DEFINE_EXECUTE_AT_END name void name void define DEFINE_EXECUTE_AT_EXIT name void name void define DEFINE_EXECUTE_FROM_GUI name libname mode void name char libname int mode define DEFINE_EXECUTE_ON_LOADING name libname void name char libname define DEFINE_INIT mame domain void name Domain domain define DEFINE_ON_DFMAND name void name void define DEFINE_RW_FILE name fp void name FILE fp Release 12 0 ANSYS Inc January 26 2009 B 1 DEFINE Macro Definitions B 2 Model Specific DEFINE Macro Definitions The following definitions for model specific DEFINE macros see Section 2 3 Model Specific DEFINE Macros are taken from the udf h header file define DEFINE_CHEM_STEP name c t p num_p n_spe
192. DEF INE Macros 2 2 2 DEFINE_DELTAT Description DEFINE DELTAT is a general purpose macro that you can use to control the size of the time step during the solution of a transient problem Note that this macro can be used only if Adaptive is selected from the Time Stepping Method drop down list in the Run Calculation task page in ANSYS FLUENT Usage DEFINE DELTAT name d Argument Type Description symbol name UDF name Domain d Pointer to domain over which the time stepping control function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns real There are two arguments to DEFINE_DELTAT name and domain You supply name the name of the UDF domain is passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the real value of the physical time step and return it to the solver Example The following UDF named mydeltat is a simple function that shows how you can use DEFINE_DELTAT to change the value of the time step in a simulation First CURRENT_TIME is used to get the value of the current simulation time which is assigned to the variable flow_time Then for the first 0 5 seconds of the calculation a time step of 0 1 is set A time step of 0 2 is set for the remainder of the simulation The time step variable is then returned to the sol
193. DEFINE_MASS_TRANSFER Description You can use DEFINE_MASS_TRANSFER when you want to model mass transfer in a multi phase problem The mass transfer rate specified using a DEFINE_MASS_TRANSFER UDF is used to compute mass momentum energy and species sources for the phases involved in the mass transfer For problems in which species transport is enabled the mass transfer will be from one species in one phase to another species in another phase If one of the phases does not have a mixture material associated with it then the mass transfer will be with the bulk fluid of that phase Usage DEFINE_MASS_TRANSFER name c mixture_thread from_phase_index from_species_index to_phase_index to_species_index Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name cellt c Index of cell on the thread pointed to by mixture_thread Thread mixture_thread Pointer to mixture level thread int from_phase_index Index of phase from which mass is transferred int from_species_index ID of species from which mass is transferred ID 1 if phase does not have mixture material int to_phase_index Index of phase to which mass is transferred int to_species_index ID of species to which mass is transferred ID 1 if phase does not have mixture material Function returns re
194. DEFINE_UDS_FLUX name f t i real name face_t f Thread t int i define DEFINE_UDS_UNSTEADY name c t i apu su void name cell_t c Thread t int i real apu real su Release 12 0 ANSYS Inc January 26 2009 DEFINE Macro Definitions B 8 Release 12 0 ANSYS Inc January 26 2009 Appendix C Quick Reference Guide for Multiphase DEF INE Macros This appendix is a reference guide that contains a list of general purpose DEFINE macros Section 2 3 Model Specific DEFINE Macros and multiphase specific DEFINE macros Sec tion 2 4 Multiphase DEFINE Macros that can be used to define multiphase model UDFs See Section 1 10 Special Considerations for Multiphase UDFs for information on special considerations for multiphase UDFs C 1 VOF Model Tables C 1 1 C 1 3 list the variables that can be customized using UDFs for the VOF multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Table C 1 1 DEFINE Macro Usage for the VOF Model Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction DEFINE PROFILE secondary phase s velocity magnitude DEFINE PROFILE mixture pressure DEFINE_PROFILE mixture temperature DEFINE PROFILE mixture mass flux DEFINE_PROFILE primary and secondary phase s species mass fractions DEFINE PROFILE phase dependent internal emissivity DEFINE PROFILE mixture user
195. DO Diffuse Reflectivity drop down list in the User Defined Function Hooks dialog box and click OK Release 12 0 ANSYS Inc January 26 2009 6 19 Hooking UDFs to ANSYS FLUENT See Section 2 3 4 DEFINE_DOM_DIFFUSE_REFLECTIVITY for details about DEFINE_DOM_DIFFUSE_REFLECTIVITY functions 6 2 5 Hooking DEFINE_DOM_SOURCE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 7 in ANSYS FLUENT i The discrete ordinates DO radiation model must be enabled from the Radiation Model dialog box To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 7 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End i Read Case i Write Case Read Data Write Data i Execute at Exit Wall Heat Flux Chemistry Step DO Source RRP SIT RT s DO Diffuse Reflectivity DO Specular Reflectivity DO Emissivity Weighting Factor Figure 6 2 7 The User Defined Function Hooks Dialog Box Select the function name e g dom libudf in the DO Source drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 5 DEFINE_DOM_SOURCE for detail
196. DS_FLUX Additional pre defined macros that you can use when coding scalar flux UDFs are provided in Section 3 2 8 User Defined Scalar UDS Trans port Equation Macros Unsteady UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply a unique UDF for the unsteady function Recall that ANSYS FLUENT computes the unsteady term in the UDS equation Scalar Unsteady UDFs are defined using the DEFINE_UDS_UNSTEADY macro Section 2 7 4 DEFINE_UDS_UNSTEADY Additional pre defined macros that you can use when coding scalar unsteady UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros Source Term UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply a unique UDF for each source Recall that ANSYS FLUENT computes the source term in the UDS equation Scalar source UDFs are defined using the DEFINE_SOURCE macro and must compute the source term Sgp and its derivative att Section 2 3 19 DEFINE_SOURCE Additional pre defined macros that you can use when coding scalar source term UDFs are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros Fixed Value Boundary Condition UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply
197. Defined Function Hooks Dialog Box Select the function name e g myrate libudf in the Volume Reaction Rate Function drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 27 DEFINE_VR_RATE for details about DEFINE_VR_RATE functions Release 12 0 ANSYS Inc January 26 2009 6 53 Hooking UDFs to ANSYS FLUENT 6 2 28 Hooking DEFINE_WALL_FUNCTIONS UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_WALL_FUNCTIONS UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model dialog box Figure 6 2 37 in ANSYS FLUENT gt DES Mea Eai Viscous Model Model Model Constants O Inviscid 2 Epsilon O Laminar 19 Spalart Allmaras 1 eqn kcepsilon 2 eqn TKE Prandtl Number Ok omega 2 eqn M O Transition k kl omega 3 eqn Oo n O Transition 55T 4 eqn TDR Prandtl Number O Reynolds Stress 7 eqn TE Detached Eddy Simulation O Large Eddy Simulation LES Energy Prandtl Number k epsilon Model 0 85 O Standard ORNG User Defined Functions Realizable Turbulent Viscosity Near Wall Treatment slat Standard Wall Functions Prandtl Numbers O Non Equilibrium Wall Functions TKE Prandtl Number Enhanced Wall Treatment User Defined Wall Functions none TDR Prandtl Number no
198. Description symbol name UDF name cellt c Index that identifies the cell that the particle is currently in Thread t Pointer to the thread the particle is currently in int initialize Variable that has a value of 1 when the function is called at the start of the particle integration and 0 thereafter Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked Function returns void There are five arguments to DEFINE_DPM_SCALAR_UPDATE name c t initialize and p You supply name the name of the UDF c t initialize and p are variables that are passed by the ANSYS FLUENT solver to your UDF i Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Also the real array user is available for stor age The size of this array should be set in the Discrete Phase Model dialog box in the Number of Scalars field Example The following compiled UDF computes the melting index along a particle trajectory The DEFINE_DPM_SCALAR_UPDATE function is called at every particle time step in ANSYS FLUENT and requires a significant amount of CPU time to execute The melting index is computed from t1 melting index dt 2 5 1 o p Also included in this UDF is an initialization function DEFINE_INIT that is used to initialize the scalar variables DPM_OUTPUT is used
199. Detailed UDF Examples 8 1 Step By Step UDF Example The following 7 step process can be used to code a UDF and use it effectively in your ANSYS FLUENT model 8 1 1 1 Process Overview Define your problem Section 8 1 2 Step 1 Define Your Problem Create a C source code file Section 8 1 3 Step 2 Create a C Source File Start ANSYS FLUENT and read in or set up the case file Section 8 1 4 Step 3 Start ANSYS FLUENT and Read or Set Up the Case File Interpret or compile the source file Section 8 1 5 Step 4 Interpret or Compile the Source File Hook the UDF to ANSYS FLUENT Section 8 1 6 Step 5 Hook the UDF to ANSYS FLUENT Run the calculation Section 8 1 7 Step 6 Run the Calculation Analyze the numerical solution and compare it to expected results Section 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results To begin the process you ll need to define the problem you wish to solve using a UDF Step 1 For example suppose you want to use a UDF to define a custom boundary profile for your model You will first need to define the set of mathematical equations that describes the profile Release 12 0 ANSYS Inc January 26 2009 8 1 Examples Next you will need to translate the mathematical equation conceptual design into a function written in the C programming language Step 2 You can do this using any text editor Save the file with a c suffix
200. E a SEES A T 3 6 oe Face MATOS e sgir eor ooh ee d a ee EE wee A are ed 3 22 woo Connectivity Nats esr ais r ata 424 Boe eos HK pa oO 3 25 Sot Special Macros 2 422 268 244444454 44 484 545 3 29 3 227 ModelSpecile Macros ead booed Bee Pa GES G 3 36 3 2 8 User Defined Scalar UDS Transport Equation Macros 3 44 3 2 9 User Defined Memory UDM Macros 3 47 va Looping Macro o gt oh ee cr es ct eae et ee a a Eg eo Ye Be Be a 3 56 3 3 1 Multiphase Looping Macros 20 4 we a eee we ee Ge Gone 5 3 60 3 3 2 Advanced Multiphase Macros 000 3 64 IV Release 12 0 ANSYS Inc January 26 2009 CONTENTS 3 4 Vector and Dimension Macros 64 48 eee ed ee eRe ee eS 3 4 1 Macros for Dealing with Two and Three Dimensions 34 2 The NO Macros o lt neck enie s bee fe he ke ae RO 343 The NV Magis ocas ea ee Ba eee gie Pa Sada g 94 4 Vector Operation Macros 2 5 6 2b ee eee nee ee 3 5 Time Dependent Macros 0 000 20 eee eee 30 Scheme Macros e erase oss BS Ha Se EE eS RES EN ws 3 6 1 Defining a Scheme Variable in the Text Interface 3 6 2 Accessing a Scheme Variable in the Text Interface 3 6 3 Changing a Scheme Variable to Another Value in the Text Interface oos ge ek ee Oe Ro ee Ba e a ee eS 3 6 4 Accessing a Scheme Variable in a UDF 31 a ne OS s aces ee ee Ee ES ESS 3 8 Miscellaneous Macros 0 00 er eee ee ee ee 4 Interpr
201. ED_UDM Compute assign Tmax at each cell real ud_eval_cell_tmax cell_t c Thread t real tmax 0 Compute cell based Tmax value tmax 1 1 C_T c t This is only an example return tmax DEFINE_NOX_RATE user_nox c t Pollut Pollut_Par NOx Assign cell based Tmax value POLLUT_CTMAX Pollut_Par ud_eval_cell_tmax c t POLLUT_CTMAX Pollut_Par C_UDMI c t CELL_TMAX DEF INE_ON_DEMAND init_tmax Domain domain register Thread t register cell_t c Message Computing Storing cell Tmax values n domain Get_Domain 1 Store User Defined Tmax at each cell if ud_nox_do_once 1 if n_udm lt N_REQUIRED_UDM Error Not enough udm allocated n thread_loop_c t domain Release 12 0 ANSYS Inc January 26 2009 2 57 DEFINE Macros begin_c_loop c t C_UDMI c t CELL_TMAX ud_eval_cell_tmax c t end_c_loop c t ud_nox_do_once 0 Message Computing cell Tmax values completed n Hooking a NO Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_NOX_RATE is compiled Chapter 5 Com piling UDF the name of the argument that you supplied as the first DEFINE macro argument e g user_nox will become visible and selectable in the NOx Model dialog box in ANSYS FLUENT See Section 6 2 12 Hooking DEFINE NOX RATE UDFs for details 2 3 13 DEFINE PR RATE Description You can use DEFINE_PR_RATE to specify a cu
202. EE oo o A A IK KK 1 1 o kkk k kkk kkk kkk include udf h DEFINE_DPM_PROPERTY coal_emissivity c t p real mp0 P_INIT_MASS p real mp P_MASS p real vf cf get the material char and volatile fractions and store them in vf and cf vf DPM_VOLATILE_FRACTION p cf DPM_CHAR_FRACTION p if mp mpO gt 1 mp mp0 lt 0 if mp mp0 lt 1 vf cf only ash left vf cf 0 return 001 else if mp mp0 lt 1 vf Release 12 0 ANSYS Inc January 26 2009 2 1 87 DEFINE Macros only ash and char left cf 1 1 vf cf mp mpod vf 0 return 1 0 else volatiles char and ash left cf cf mp mp0 vf 1 1 vf mp mp0 return 1 0 return 1 0 DEFINE_DPM_PROPERTY coal_scattering c t p real mp0 P_INIT_MASS p real mp P_MASS p real cf vf get the original char and volatile fractions and store them in vf and cf vf DPM_VOLATILE_FRACTION p cf DPM_CHAR_FRACTION p if mp mpO gt 1 mp mp0 lt 0 if mp mp0 lt 1 vf cf only ash left vf cf 0 return 1 1 else if mp mp0 lt 1 vf only ash and char left cf 1 1 vf cf mp mpod vf 0 return 0 9 2 1 88 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros el
203. EFINE macro argument e g heat_flux will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 9 Hooking DEFINE_HEAT_FLUX UDFs for details 2 46 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 10 DEFINE_IGNITE_SOURCE Description You can use DEFINE_IGNITE_SOURCE to customize the ignition time source term in the autoignition model model Usage DEFINE_IGNITE_SOURCE name c t source Argument Type Description symbol name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the ignition source term is to be applied real source Pointer to the ignition source term Function returns void There are four arguments to DEFINE_IGNITE_SOURCE name c t and source You supply name the name of the UDF c t and source are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the value referenced by the source pointer as shown in the example below Example The following UDF named ign_udf_src specifies a custom source term in the ignition model The source code must be executed as a compiled UDF in ANSYS FLUENT In the standard ignition model in ANSYS FLUENT the source term for the ignition progress variable is given by a Livengood Wu integral 7 t dt I 2 3 4 to Tig where dt is the flow time step and Tig is the correlation between spark time and knock by Douaud
204. EFINE_DPM_INJECTION_INIT name I void name Injection I define DEFINE_DPM_LAW name p ci void name Tracked_Particle p int ci define DEFINE_DPM_OUTPUT name header fp p t plane void name int header FILE fp Tracked_Particle p Thread t Plane plane define DEFINE_DPM_PROPERTY name c t p real name cell_t c Thread t Tracked_Particle p define DEFINE_DPM_SCALAR_UPDATE name c t initialize p void name cell_t c Thread t int initialize Tracked_Particle p define DEFINE_DPM_SOURCE name c t S strength p void name cell_t c Thread t dpms_t S real strength Tracked_Particle p define DEFINE_DPM_SPRAY_COLLIDE name tp p B 6 Release 12 0 ANSYS Inc January 26 2009 B 6 User Defined Scalar UDS DEFINE Macros void name Tracked_Particle tp Particle p define DEFINE_DPM_SWITCH name p ci void name Tracked_Particle p int ci define DEFINE_DPM_TIMESTEP name p ts real name Tracked_Particle p real ts define DEFINE_DPM_VP_EQUILIB name p cvap_surf void name Tracked_Particle p real cvap_surf B 6 User Defined Scalar UDS DEFINE Macros The following definitions for UDS DEFINE macros see Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros are taken from the udf h header file define DEFINE_ANISOTROPIC_DIFFUSIVITY name c t ns dmatrix void name cell_t c Thread t int ns real dmatrix ND_ND ND_ND define
205. ENT After the UDF that you have defined using DEFINE DPM VP EQUILIBRIUM is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the Create Edit Materials dialog box in ANSYS FLUENT Note that before you hook the UDF yov ll need to create particle injections in the Injections dialog box with the type Multicomponent chosen See Section 6 4 15 Hooking DEFINE_DPM_VP_EQUILIB UDFs for details on how to hook your DEFINE DPM VP_EQUILIB UDF to ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 2 207 DEFINE Macros 2 6 Dynamic Mesh DEFINE Macros This section contains descriptions of DEFINE macros that you can use to define UDFs that control the behavior of a dynamic mesh Note that dynamic mesh UDF that are defined using DEFINE_CG_MOTION DEFINE_DYNAMIC_ZONE_PROPERTY DEFINE_GEOM and DEFINE GRID MOTION can only be executed as compiled UDFs Table 2 6 1 provides a quick reference guide to the dynamic mesh DEFINE macros the functions they define and the dialog boxes where they are activated in ANSYS FLU ENT Definitions of each DEFINE macro are contained in the udf h header file For your convenience they are listed in Appendix B e Section 2 6 1 DEFINE CG MOTION Section 2 6 2 DEFINE_DYNAMIC_ZONE_PROPERTY Section 2 6 3 DEFINE_GEOM Section 2 6 4 DEFINE_GRID_MOTION Section 2 6 5
206. ENTS_EXT THREAD_N_ELEMENTS_INT Data Array for pressure on thread C_P c t THREAD_N_ELEMENTS Figure 7 2 3 Exterior Thread Data Storage at End of a Thread Array negated forms direct the compiler to include only portions of the function that apply to a particular process and ignore the rest see Section 7 5 1 Compiler Directives A general rule of thumb is that your serial UDF needs to be parallelized if it performs an operation that is dependent on sending or receiving data from another compute node or the host UDFs that involve global reductions such as global sums minimums or maximums or ones that perform computations on data residing in adjacent compute nodes for example will need to be modified in order to run in parallel Some other types of operations that require parallelization of serial source code include the following e Reading and Writing Files e Global Reductions e Global Sums e Global Minimums and Maximums e Global Logicals e Certain Loops over Cells and Faces e Displaying Messages on a Console e Printing to a Host or Node Process 7 10 Release 12 0 ANSYS Inc January 26 2009 7 4 Parallelization of Discrete Phase Model DPM UDFs After the source code for your parallelized UDF has been written it can be compiled using the same methods for serial UDFs Instructions for compiling UDFs can be found in Chapter 5 Compiling UDFs 7 4 Parallelization of Discrete Phase Mode
207. EP return source Hooking a Source UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SOURCE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g xmom source will become visible and selectable in the Fluid or Solid cell zone condition dialog box in ANSYS FLU ENT See Section 6 2 19 Hooking DEFINE_SOURCE UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 1 05 DEFINE Macros 2 3 20 DEFINE_SOX_RATE Description You can use DEFINE_SOX_RATE to specify a custom SO rate that can either replace the internally calculated SO rate in the source term equation or be added to the ANSYS FLUENT rate Example 1 demonstrates this use of DEFINE_SOX_RATE The default func tionality is to add user defined rates to the ANSYS FLUENT calculated rates If the Replace with UDF Rate option is enabled in the SOx Model dialog box then the ANSYS FLUENT calculated rate will not be used and it will instead be replaced by the SO rate you have defined in your UDF When you hook a SO rate UDF to the graphical interface without checking the Replace with UDF Rate box then the user defined SO rate will be added to the internally calculated rate for the source term calculation DEFINE_SOX_RATE may also be used to calculate the upper limit for the integration of the temperature PDF when temperature is accounte
208. F In the UDF presented below a charged particle is introduced upstream into a laminar flow and travels downstream until t tstart when a magnetic field is applied The particle takes on an approximately circular path not an exact circular path because the speed and magnetic force vary as the particle is slowed by the surrounding fluid The macro P_TIME p gives the current time for a particle traveling along a trajectory which is pointed to by p UDF for computing the magnetic force on a charged particle include udf h define Q 1 0 particle electric charge define BZ 3 0 z component of magnetic field define TSTART 18 0 field applied at t tstart Calculate magnetic force on charged particle Magnetic force is particle charge times cross product of particle velocity with magnetic field Fx q bz Vy Fy q bz Vx DEF INE_DPM_BODY_FORCE particle_body_force p i real bforce 0 if P_TIME p gt TSTART if i 0 bforce Q BZ P_VEL p 1 else if i 1 bforce Q BZ P_VEL p 0 2 1 64 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros else bforce 0 0 an acceleration should be returned return bforce P_MASS p Hooking a DPM Body Force UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DPM BODY FORCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name o
209. F It is executed as an interpreted UDF in ANSYS FLUENT Adding a Momentum Source to a Duct Flow When a source term is being modeled with a UDF it is important to understand the context in which the function is called When you add a source term ANSYS FLUENT will call your function as it performs a global loop on cells Your function should compute the source term and return it to the solver In this example a momentum source will be added to a 2D Cartesian duct flow The duct is 4 m long and 2 m wide and will be modeled using a symmetry boundary through the middle Liquid metal with properties listed in Table 8 2 1 enters the duct at the left with a velocity of 1 mm s at a temperature of 290 K After the metal has traveled 0 5 m along the duct it is exposed to a cooling wall which is held at a constant temperature of 280 K To simulate the freezing of the metal a momentum source is applied to the metal as soon as its temperature falls below 288 K The momentum source is proportional to the x component of the velocity vz and has the opposite sign S Ov 8 2 1 where C is a constant As the liquid cools its motion will be reduced to zero simulating the formation of the solid In this simple example the energy equation will not be customized to account for the latent heat of freezing The velocity field will be used only as an indicator of the solidification region The solver linearizes source terms in order to enhance the st
210. F user_gray_band_abs c t nb real abs_coeff 0 real T C_T c t switch nb case 0 abs_coeff 1 3 0 001 T break case 1 abs_coeff 2 7 0 005 T break return abs_coeff J Hooking a Gray Band Coefficient UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE GRAY BAND ABS COEFF is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_gray_band_abs will become visible and selectable in the Create Edit Materials dialog box for the Absorption Coefficient See Section 6 2 8 Hooking DEFINE GRAY BAND ABS COEFF UDFs for details 2 44 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 9 DEFINE_HEAT_FLUX Description You can use DEFINE HEAT FLUX to modify the heat flux at a wall Despite the name a DEFINE_HEAT FLUX UDF is not the means to specify the actual heat flux entering a domain from the outside To specify this type of heat flux you would simply use a DEFINE_PROFILE function in conjunction with a heat flux thermal boundary condition In contrast a DEFINE_HEAT_FLUX UDF allows you to modify the way in which the de pendence between the flux entering the domain and the wall and cell temperatures is modeled Fa This function allows you to modify the heat flux at walls adjacent to a solid Note however that for solids since only heat conducti
211. FIT define CC1 453 577 define CC2 1 65014 define CC3 1 24814e 3 define CC4 3 78201e 7 define CC5 0 00 REFERENCE STATE define P_REF 101325 define T_REF 288 15 OPTIONAL REFERENCE OFFSET VALUES FOR ENTHALPY AND ENTROPY define H_REF 0 0 define S_REF 0 0 static int usersMessage char static void usersError char Static variables associated with Redlich Kwong Model static double rgas a0 bO c0 bb cp_int_ref DEF INE_ON_DEMAND I_do_nothing this is a dummy function to allow us to use the compiled UDFs utility 5 FUNCTION RKEOS_error void RKEOS_error int err char f char msg if err usersError RKEOS_error d from function s n s n err f msg 8 56 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples FUNCTION RKEOS_Setup void RKEOS_Setup Domain domain cxboolean vapor_phase char filename int messagefunc char format void errorfunc char format rgas RGASU MWT a0 0 42747 rgas rgas TCRIT TCRIT PCRIT bO 0 08664 rgas TCRIT PCRIT cO rgas TCRIT PCRIT a0 VCRIT VCRIT b0 bO VCRIT bb b0 c0 cp_int_ref CC1 log T_REF T_REF CC2 T_REF 0 5 CC3 T_REF 0 3333
212. FLUENT about 6 1 DPM 6 63 dynamic mesh 6 81 errors 6 95 general purpose 6 1 model specific 6 13 multiphase 6 55 UDS 6 90 user defined scalars 6 90 host_to_node 7 15 I O functions A 14 AM_NODE_HOST_P 7 17 AM_NODE_LAST_P 7 17 AM_NODE_LESS_P 7 17 AM_NODE_MORE_P 7 17 AM_NODE_ONE_P 7 17 AM_NODE_SAME_P 7 17 AM_NODE_ZERO_P 7 17 7 40 Release 12 0 ANSYS Inc January 26 2009 identifying processes parallel 7 35 if statement A 10 if else statement A 10 ignition model UDFs source term 2 47 in cylinder applications 2 211 In Cylinder Output Controls dialog box 6 82 incident radiation 8 43 include A 17 initialization UDFs 2 18 Injections dialog box 6 68 6 69 6 71 6 78 input output functions A 14 interaction domains 1 17 interior cell looping macro parallel 7 22 interior faces partitioned mesh 7 28 INTERIOR_ FACE_GEOMETRY 3 27 Interpreted UDFs dialog box 4 1 4 3 4 5 8 6 8 7 interpreted UDFs 1 2 1 6 4 1 4 3 C compiler 1 7 C preprocessor 1 6 errors in interpreting source file 4 5 example 8 30 interpreter 1 6 restrictions 1 7 Windows parallel network 4 3 writing case files 4 5 interpreted vs compiled UDFs 1 7 interpreting source files about 4 3 procedure 4 3 interpreting UDF source files 4 1 irix6 5 5 16 iteration UDFs execute at exit 2 10 k e turbulence model 2 125 k w turbulence model 2 125 laminar flow speed 2 87 LES turbulence model
213. G A 2 210 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros end_f_loop f t compute change in velocity i e dv F dt mass velocity update using explicit Euler formula dv dtime force 50 0 v_prev dv Message time f x_vel f force f n time v_prev force set x component of velocity vel 0 v_prev Hooking a Center of Gravity Motion UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_CG_MOTION is compiled Chapter 5 Com piling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Mesh Zones dialog box in ANSYS FLUENT See Section 6 5 1 Hooking DEFINE CG MOTION UDFs for details on how to hook your DEFINE_CG_MOTION UDF to ANSYS FLUENT 2 6 2 DEFINE_DYNAMIC_ZONE_PROPERTY Description The DEFINE_DYNAMIC_ZONE_PROPERTY UDF can be used in the following applications e swirl center definition for in cylinder applications e variable cell layering height Swirl Center Definition for In Cylinder Applications You can use DEFINE_DYNAMIC_ZONE_PROPERTY to calculate swirl center while computing in cylinder specific output Note that UDFs that are defined using DEFINE_DYNAMIC_ZONE_PROPERTY can only be executed as compiled UDFs For information on setting in cylinder parameters see Section 11 3 6 Setting In Cylinder Parameters in the separate User s Guide Release 12 0
214. Hooking a Chemistry Step UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_CHEM_STEP is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_chem_step will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 1 Hooking DEFINE_CHEM_STEP UDFs for details 2 32 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 2 DEFINE_CPHI Description You can use DEFINE_CPHI to set the value of the mixing constant Cy see Equation 11 3 4 and Equation 11 3 6 in the separate Theory Guide for details It is useful for modeling flows where Cy departs substantially from its default value of 2 which occurs at low Reynolds and or high Schmidt numbers Usage DEF INE_CPHI name c t Argument Type Description symbol name UDF name celltc Cell index Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_CPHI name c and t You supply name the name of the UDF c and t are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the real value of the mixing constant Cy and return it to the solver Hooking a Mixing Constant UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_CPHI is interpreted Chapter 4 In terpreting UDFs or compiled Cha
215. IDT UDF DEFINE_TURBULENT_VISCOSITY DEFINE _VR_RATE DEFINE WALL FUNCTIONS Table 2 3 1 Quick Reference Guide for Model Specific DEFINE Functions Function DEFINE Macro Dialog Box Activated In mixing constant homogeneous net mass reaction rate for all species integrated over a time step species mass or UDS diffusivity diffusive reflectivity for discrete ordinates DO model source for DO model specular reflectivity for DO model emissivity weighting factor for the RTE of the non gray DO model gray band absorption coefficient for DO model wall heat flux ignition time source homogeneous net mass reaction rate for all species DEFINE_CPHI DEF INE_CHEM_STEP DEFINE_DIFFUSIVITY DEFINE _DOM_DIFFUSE_ REFLECTIVITY DEF INE_DOM_SOURCE DEF INE_DOM_SPECULAR_ REFLECTIVITY DEFINE_EMISSIVITY_ WEIGHTING FACTOR DEFINE_GRAY_BAND_ ABS_COEFF DEFINE HEAT FLUX DEFINE IGNITE SOURCE DEF INE_NET_ REACTION_RATE User Defined Function Hooks User Defined Function Hooks Create Edit Materials User Defined Function Hooks User Defined Function Hooks User Defined Function Hooks User Defined Function Hooks Create Edit Materials User Defined Function Hooks User Defined Function Hooks User Defined Function Hooks Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Table 2 3 2 Quick Reference Guide for Model Specific DEFINE Functions Continued F
216. INE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF INE_SOURCE boundary condition Wall boundary condition Phase Interaction Phase Interaction Phase Interaction Phase Interaction Create Edit Materials Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase Secondary Phase boundary condition Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 1 DEFINE_CHEM_STEP Description You can use DEFINE_CHEM_STEP to specify the change in mass fraction due to homogeneous reaction over a time step dY Zi q 2 3 1 At y f 0 where Y is the initial mass fraction of species 7 t is time At is the given time step and oe is the net rate of change of the ith species mass fraction Y is ith species mass fraction at the end of the integration DEFINE CHEM STEP UDFs are used for the Laminar finite rate with Stiff Chemistry en abled EDC and PDF Transport models Usage DEF INE_CHEM_STEP name c t p num_p n_spe dt pres temp yk Argument Type Description symbol name UDF name cell_tc Cell index of current particle Thread t Pointer to cell thread for particle Particle p Pointer to particle data struct
217. INE ON DEMAND func tions 6 1 7 Hooking DEFINE_RW_FILE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_RW_FILE UDF it is ready to be hooked to ANSYS FLUENT Note that you can hook multiple read write file UDFs to your model if desired To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 1 11 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Figure 6 1 11 The User Defined Function Hooks Dialog Box You have the choice of hooking a UDF to read and write a case and data file Below is a description of what each function does e Read Case is called when you read a case file into ANSYS FLUENT It will specify the customized section that is to be read from the case file e Write Case is called when you write a case file from ANSYS FLUENT It will specify the customized section that is to be written to the case file Release 12 0 ANSYS Inc January 26 2009 6 11 Hooking UDFs to ANSYS FLUENT e Read Data is called when you read a data file into ANSYS FLUENT It will specify the customized section that is to be read from the data file e Write Data is called when you write a data
218. INE_NOX_RATE name c t Pollut Pollut_Par and NOx You will supply name the name of the UDF c t Pollut Pollut Par and NOx are variables that are passed by the ANSYS FLUENT solver to your function A DEFINE_NOX_RATE function does not output a value The calculated NO rates or other pollutant species rates are returned through the Pollut structure as the forward rate POLLUT_FRATE Pollut and reverse rate POLLUT_RRATE Pollut respectively i The data contained within the NO structure is specific only to the NO model Alternatively the Pollut structure contains data at each cell that are useful for all pollutant species e g forward and reverse rates gas phase temperature density The Pollut Par structure contains auxil iary data common to all pollutant species e g equation solved universal gas constant species molecular weights Note that molecular weights ex tracted from the Pollut_Par structure i e Pollut_Par gt sp IDX i mw for pollutant species NO HCN etc and Pollut _Par gt sp i mw for other species such as O2 has units of kg kg mol Release 12 0 ANSYS Inc January 26 2009 2 53 DEFINE Macros Example 1 The following compiled UDF named user_nox exactly reproduces the default ANSYS FLUENT NO rates for the prompt NO pathway Note that this UDF will replace the ANSYS FLUENT rate only if you select Replace FLUENT Rate in the UDF Rate group box in the Prompt tab Otherwise the rate comput
219. JUST UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Usage DEFINE_ADJUST name d Argument Type Description symbol name UDF name Domain d Pointer to the domain over which the adjust function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns void There are two arguments to DEFINE_ADJUST name and d You supply name the name of the UDF d is passed by the ANSYS FLUENT solver to your UDF 2 4 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Example 1 The following UDF named my_adjust integrates the turbulent dissipation over the entire domain using DEFINE_ADJUST This value is then displayed in the console The UDF is called once every iteration It can be executed as an interpreted or compiled UDF in ANSYS FLUENT POR o oo o o kkk 21 21 21 A A A A A kk KK KEK UDF for integrating turbulent dissipation and displaying it in the console BOA AAR I I ARIA RI A A I KKK KEK kkk kk kkk k kkk include udf h DEFINE_ADJUST my_adjust d Thread t Integrate dissipation real sum_diss 0 cell_t c thread_loop_c t d begin_c_loop c t sum_diss C_D c t C_VOLUME c t end_c_loop c t printf Volume integral of turbulent dissipation g n sum_diss Release 12 0 ANSYS Inc
220. LE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEF INE_DPM_BC phase dependent mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture Release 12 0 ANSYS Inc January 26 2009 C 2 Mixture Model Table C 1 3 DEFINE Macro Usage for the VOF Model Variable Macro Phase Specified On Other surface tension coefficient DEFINE_PROPERTY phase interaction mass transfer coefficient DEFINE MASS_TRANSFER phase interaction heterogeneous reaction rate DEFINE HET RXN_RATE phase interaction C 2 Mixture Model Tables C 2 1 C 2 3 list the variables that can be customized using UDFs for the Mixture multiphase model the DEFINE macros that are used to define the UDF and the phase that the UDF needs to be hooked to for the given variable Table C 2 1 DEFINE Macro Usage for the Mixture Model Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction DEFINE PROFILE secondary phase s mass flux DEFINE PROFILE primary and secondary phase s velocity magnitude DEFINE_PROFILE primary and secondary phase s pressure DEFINE PROFILE mixture temperature DEFINE PROFILE mixture species mass fractions DEFINE_PROFILE phase dependent user defined scalar boundary va
221. LENGTH name c t Argument Type Description symbol name UDF name cellt c Index of cell on which the transition length function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE _TRANS_FLENGTH name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the transition length function to the solver 2 1 18 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example An example of a TRANS_FLENGTH UDF is provided at the end of this section Hooking a Transition Correlation UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_TRANS_FLENGTH is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the DEFINE macro argument e g user_Flength will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 23 Hooking DEFINE_TRANS UDF for details DEFINE_TRANS_RETHETA_C Description You can use DEFINE_TRANS_RETHETA_C to specify the critical momentum thickness Reynolds number for the Transition SST turbulence model Usage DEFINE_TRANS_RETHETA_C name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the critical momentum thickness Reynold
222. M_INJECTION_INIT for details about DEFINE_DPM_INJECTION_INIT functions 6 4 6 Hooking DEFINE_DPM_INJECTION_INIT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_INJECTION_INIT UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Set Injection Properties dialog box Figure 6 4 6 in ANSYS FLUENT To hook the UDF first create a particle injection in the Injections dialog box Define Injections Click Create in the Injections dialog box to open the Set Injection Properties dialog box Figure 6 4 6 Set up the particle injection in the Set Injection Properties dialog box Then click the UDF tab and select the function name e g init_bubbles libudf from the Initialization drop down list under User Defined Functions Click OK See Section 2 5 6 DEFINE _DPM_INJECTION_INIT for details about DEFINE DPM_INJECTION_INIT functions Release 12 0 ANSYS Inc January 26 2009 6 69 Hooking UDFs to ANSYS FLUENT amp Set Injection Properties Injection Name injection 0 Injection Type 3 single v Particle Type Laws OMassless Inert Droplet OcCombusting Multicomponent C Custom Material t ribu J Sf Discrete Phase Domain anthracite v none Point Properties Turbulent Dispersion Wet Combustion Components UDF multiple Reactions User Defi
223. N and iwork where x is an array N is the number of elements in the array and iwork is an array that is of the same type and size as x which is needed for temporary storage Macros of this type are passed an array x and the elements of array x are filled with the new result after returning from the function For example the macro PRF_GIHIGH x N iwork expands to a function that computes the maximum of each element of the array x over all the compute nodes uses the array iwork for temporary storage and modifies array x by replacing each element with its resulting global maximum The function does not return a value Example Global Reduction Variable Array Macro real x N iwork N The elements of x are set in the working array here and will have different values on each compute node In this case x 0 could be the maximum cell temperature of all the cells on the compute node x 1 the maximum pressure x 2 the maximum density etc PRF_GRHIGH x N iwork The maximum value for each value over all the compute nodes is found here The elements of x on each compute node now hold the same maximum values over all the compute nodes for temperature pressure density etc Release 12 0 ANSYS Inc January 26 2009 7 19 Parallel Considerations Global Summations Macros that can be used to compute global sums of variables are identified by the suf fix SUM PRF_GISUM1 and PRF_GISUM compute the global sum
224. ND UDF sets the initial val ues of the UDM locations using udf_offset which is defined in the EXECUTE ON LOADING UDF Note that the on demand UDF must be executed after the solution is initialized to reset the initial values for the UDMs Release 12 0 ANSYS Inc January 26 2009 3 51 Additional Macros for Writing UDFs The following describes the process of reserving five UDMs for two libraries named 1libudf and libudf2 1 In the User Defined Memory dialog box specify 5 for the Number of User Defined Memory Locations 2 In the Compiled UDFs dialog box build the compiled library named libudf for udm res1 c and load the library 3 Build the compiled library for udm_res2 c named libudf2 and load the library 4 Initialize the solution 5 Execute the on demand UDFs for libudf and libudf2 in the Execute On Demand dialog box 6 Iterate the solution 7 Postprocess the results Example 1 pLa kkk k kkk kkk kkk kkk kk kkk kkk kk kk k kkk kk k kkk kkk k k k k k udm_res1 c contains two UDFs an execute on loading UDF that reserves three UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs EEEE ooo o kk kkk kkk kkk kk kkk include udf h define NUM_UDM 3 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname if udm_offset UDM_UNRESERVED udm_offset Reserve_User_Memory_Vars NUM_UDM if udm_offset
225. NE macro argument will become visible and selectable in ANSYS FLUENT To hook the UDF first make a selection from the Model list of the Multiphase Model dialog box RA Des Edit Next select Species Transport from the Model list of the Species Model dialog box Teta Sees Edit Then open the Phase Interaction dialog box Figure 6 3 5 lt EMERSA gt Interaction Phase Interaction C Wall Adhesion Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Total Number of Heterogeneous Reactions 1 S C Heterogeneous Stiff Chemistry Solver Reaction Name net reaction 1 ID 1 5 Number of Reactants a Number of Products 1 Is a Phase Species Stoich Phase Species Stoich Coefficient Coefficient phase 1 0 HE phase 1 0 Reaction Rate Function Jluser_evap_condens y Figure 6 3 5 The Phase Interaction Dialog Box Click the Reactions tab and enter a nonzero number in the Total Number of Heterogeneous Reactions text box Select the function name e g user_evap_condens_react libudf from the Reaction Rate Function drop down list and click OK See Section 2 4 3 DEFINE_HET_RXN_RATE for details about writing DEFINE_HET_RXN_RATE functions Release 12 0 ANSYS Inc January 26 2009 6 59 Hooking UDFs to ANSYS FLUENT 6 3 4 Hooking DEFINE_MASS_TRANSFER UDFs After you have interpreted Chapter 4 Interpreting UDFs or c
226. NE_PROFILE vis_res t i real x ND_ND real a cell_t c begin_c_loop c t C_CENTROID x c t if x 1 lt x 0 0 01 a 1e9 Release 12 0 ANSYS Inc January 26 2009 2 83 DEFINE Macros else a 1 0 F_PROFILE c t i a end_c_loop c t Viscous Resistance Profile UDF in a Porous Zone that utilizes C_PROFILE include udf h DEFINE_PROFILE porosity_function t nv cell_t c begin_c_loop c t C_PROFILE c t nv USER INPUT end_c_loop c t Example 7 Porous Resistance Direction Vector The following UDF contains profile functions for two porous resistance direction vectors that utilize C_LPROFILE These profiles can be hooked to corresponding direction vectors under Porous Zone in the Fluid cell zone condition dialog box Porous Resistance Direction Vector Profile that utilizes C_PROFILE include udf h DEFINE_PROFILE dir1 t nv cell_t c begin_c_loop c t C_PROFILE c t nv USER INPUT1 end_c_loop c t DEFINE_PROFILE dir2 t nv cell_t c begin_c_loop c t C_PROFILE c t nv USER INPUT2 end_c_loop c t 2 84 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 8 Target Mass Flow Rate UDF as a Function of Physical Flow Time For some unsteady problems it is desirable that the target mass flow rate be a function of the physical flow time This boundary condition can be applied using a DEFINE_PROFILE UDF The follo
227. NODE FILE fp NULL char filename press_out txt endif if PARALLEL int size data passing variables real array int pe endif Only Serial and Compute Nodes have data on threads if RP_HOST thread Lookup_Thread domain FLUID_ID endif if RP_NODE SERIAL or HOST if fp fopen filename w NULL Message n Warning Unable to open 4s for writing n filename else Message nWriting Pressure to s filename endif UDF Now does 3 different things depending on SERIAL NODE or HOST if PARALLEL SERIAL begin_c_loop c thread fprintf fp g n C_P c thread Simply write out pressure data end_c_loop c thread endif PARALLEL if RP_NODE Release 12 0 ANSYS Inc January 26 2009 7 41 Parallel Considerations Each Node loads up its data passing array size THREAD_N_ELEMENTS_INT thread array real malloc size sizeof real begin_c_loop_int c thread array c C_P c thread end_c_loop_int c thread Set pe to destination node If on node_O send data to host Else send to node_0 because compute nodes connect to node_O amp node_O to host pe I_AM_NODE_ZERO_P node_host node_zero PRF_CSEND_INT pe amp size 1 myid PRF_CSEND_REAL pe array size myid free array free array on nodes after data sent node_O now collect data sent by other compute nodes and sends it
228. NSYS Inc January 26 2009 A 9 C Programming Basics A 11 Control Statements You can control the order in which statements are executed in your C program using control statements like if if else and for loops Control statements make decisions about what is to be executed next in the program sequence A 11 1 if Statement An if statement is a type of conditional control statement The format of an if statement is if logical expression statements where logical expression is the condition to be tested and statements are the lines of code that are to be executed if the condition is met Example if q 1 a 0 b 1 A 11 2 if else Statement if else statements are another type of conditional control statement The format of an if else statement is if logical expression statements else statements where logical expression is the condition to be tested and the first set of statements are the lines of code that are to be executed if the condition is met If the condition is not met then the statements following else are executed A 10 Release 12 0 ANSYS Inc January 26 2009 A 11 Control Statements Example if x lt 0 y x 50 else X X y x 25 The equivalent FORTRAN code is shown below for comparison IF X LT 0 THEN Y X 50 ELSE X X Y X 25 ENDIF A 11 3 for Loops for loops are control statements that are a basic looping construct in C T
229. NT See Section 6 4 3 Hook ing DEFINE_DPM_DRAG UDFs for details on how to hook your DEFINE_DPM_DRAG UDF to ANSYS FLUENT 2 5 4 DEFINE_DPM_EROSION Description You can use DEFINE_DPM_EROSION to specify the erosion and accretion rates calculated as the particle stream strikes a wall surface The function is called when the particle encounters a reflecting surface Usage DEFINE_DPM_EROSION name p t f normal alpha Vmag mdot Argument Type Description symbol name UDF name Tracked_Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Thread t Pointer to the face thread the particle is currently hitting face_t f Index of the face that the particle is hitting real normal Array that contains the unit vector that is normal to the face real alpha Variable that represents the impact angle between the particle path and the face in radians real Vmag Variable that represents the magnitude of the particle velocity in m s real mdot Flow rate of the particle stream as it hits the face in kg s Function returns void Release 12 0 ANSYS Inc January 26 2009 2 1 67 DEFINE Macros There are eight arguments to DEFINE_DPM_EROSION name p t f normal alpha Vmag and mdot You supply name the name of the UDF p t f normal alpha Vmag and mdot are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the val
230. ODE if I_AM_NODE_ZERO_P Nodes 1 2 send the number of faces PRF_CSEND_INT node_zero amp n_faces 1 myid endif Allocating memory for arrays on each node p_array real malloc n_faces sizeof real x_array real ND_ND malloc ND_ND n_faces sizeof real begin_f_loop f tf Loop over interior faces in the thread filling p_array with face pressure and x_array with centroid p array f F_P f tf F_CENTROID x_array f f tf end_f_loop f tf Send data from node 1 2 to node O Message0 nstart n if RP_NODE if I_AM_NODE_ZERO_P Only SEND data from nodes 1 2 PRF_CSEND_REAL node_zero p_array n_faces myid PRF_CSEND_REAL node_zero x_array 0 ND_ND n_faces myid else endif Node O and Serial processes have their own data so list it out first MessageO n nList of Pressures n Same as Message on SERIAL for j 0 j lt n_faces j n_faces is currently node O serial value if RP_3D Message0 12 4e 12 4e 12 4e 12 4e n Release 12 0 ANSYS Inc January 26 2009 7 31 Parallel Considerations x_array j 0 x_array j 1 x_array j 2 p_arrayl jl else 2D Message0 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 p_arraylLj endif Node O must now RECV data from the other nodes and list that too if RP_NODE if I_AM_NODE_ZERO_P compute_node_loop_not_zero i See
231. Options UDS Index pe fa Solution Zones all fluid zones Flux Function mass flow rate Unsteady Function Imy_uds_unsteady libudf gt Figure 6 6 4 The User Defined Scalars Dialog Box In the User Defined Scalars dialog box Figure 6 6 4 specify the Number of User Defined Scalars e g 2 in the User Defined Scalars dialog box Figure 6 6 4 As you enter the number of user defined scalars the dialog box will expand to show the User Defined Scalars Options group box Next for each scalar you have defined increment the UDS Index and select the Zone Type and the Flux Function Then select the name of your UDF e g my_uds_unsteady libudf from the Unsteady Function drop down list and click OK 6 94 Release 12 0 ANSYS Inc January 26 2009 6 7 Common Errors While Hooking a UDF to ANSYS FLUENT 6 7 Common Errors While Hooking a UDF to ANSYS FLUENT In some cases if you select user defined as an option in a graphics dialog box but have not previously interpreted or compiled loaded a UDF you will get an error message In other graphics dialog boxes the user defined option will only become visible as an option for a parameter after you have interpreted or compiled the UDF After you have interpreted or compiled the UDF you can then select user defined option and the list of interpreted and compiled loaded UDFs will be displayed If you inadvertently hook a UDF to the wrong parameter in an ANSYS FLUENT
232. Ox 3 41 time dependent 3 1 user defined memory 3 48 3 49 user defined scalars 3 45 vector and dimension 3 1 Makefile 1 6 5 2 makefile udf 5 12 makefile udf2 5 12 makefile_nt udf 5 10 mass transfer coefficient UDFs multiphase 2 149 mass transfer UDFs 2 149 material properties 1 3 material property macros 3 18 material property UDFs general purpose 2 87 MATERIAL_PROP 2 177 2 197 MATERIAL_PROPERTY 2 89 2 92 MATERIAL_TYPE 2 197 mathematical functions A 13 mem h header file 3 6 3 7 3 19 mesh motion UDFs 2 218 meshes components domains threads cells faces 1 8 partitioned 7 7 topology 1 8 zones 1 8 Release 12 0 ANSYS Inc January 26 2009 Index Message 2 168 3 79 7 28 7 37 message displaying macros parallel 7 28 message passing parallel 7 4 example 7 30 macros 7 29 Message0 7 28 metric h header file 3 5 3 6 3 21 3 23 Microsoft Visual Studio 5 5 mixing constant UDF s 2 33 mixing law thermal conductivity 2 92 mixture domain pointer 3 67 Mixture model DEFINE macro usage C 3 mixture_species_loop 2 90 model dependent UDFs solar intensity 2 98 model specific DEFINE macros quick reference guide for 2 25 model specific UDFs hooking 6 13 models h 3 80 MOLECON 3 40 3 42 momentum source term UDF example 8 25 mp_thread_loop_c 3 62 mp_thread_loop_f 3 63 multicomponent particle heat and mass transfer UDFs 2 173 multiphase DEFINE macros quick re
233. PM BC UDFs for details on how to hook your DEFINE_DPM_BC UDF to ANSYS FLUENT 2 5 2 DEFINE DPM BODY FORCE Description You can use DEFINE_DPM_BODY_FORCE to specify a body force other than a gravitational or drag force on the particles Usage DEFINE DPM BODY FORCE name p i Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked int i An index 0 1 or 2 that identifies the Cartesian component of the body force that is to be returned by the function Function returns real There are three arguments to DEFINE_DPM_BODY_FORCE name p and i You supply name the name of the UDF p and i are variables that are passed by the ANSYS FLUENT solver Release 12 0 ANSYS Inc January 26 2009 2 1 63 DEFINE Macros to your UDF Your UDF will need to return the real value of the acceleration due to the body force in m s to the ANSYS FLUENT solver Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following UDF named particle_body_force computes the magnetic force on a charged particle DEFINE_DPM_BODY_FORCE is called at every particle time step in ANSYS FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UD
234. PM_LAW_USER_1 which refers to condenshumidlaw since only one user law has been defined The switching criterion is the local humidity which is computed in the domain using a DEFINE_ON_DEMAND function which again calls the function myHumidity for every cell In the case where the humidity is greater than 1 condensation is computed by applying a simple mass transfer calculation Otherwise one of ANSYS FLUENT s standard laws for Vaporization or Inert Heating are applied depending on the particle mass The UDF requires one UDML and needs a species called h2o to compute the local humidity Release 12 0 ANSYS Inc January 26 2009 2 1 97 DEFINE Macros DOR OOOO RK a kk ak a kk Concatenated UDFs for the Discrete Phase Model that includes a usage of DPM_SWITCH BOAR AAR I I I A A OK KOK KK 2 A A 1 21 21 21 kkk kk kkk kkk kkk include udf h include dpm h include surf h for macros RP_Cell amp RP_Thread include prop h for function Saturation_Pressure of water static real dpm_relax 1 0 dpm source relaxation real H20_Saturation_Pressure real T real ratio aTmTp aTmTp 01 T 338 15 ratio 647 286 T 1 7 419242 aTmTp 29721 aTmTp 1155286 aTmTp 8 685635e 3 aTmTp 1 094098e 3 aTmTp 4 39993e 3 aTmTp 2 520658e 3 aTmTp 5 218684e 4 return 22 089e6 exp MIN ratio 35 real myHumidity cell_t c Thread t int i Material m THRE
235. PORTING Ic Program Files ANSYS Inc v1i20 fluent fluent12 0 9 ntx86 2d Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 src Ic Program Files ANSYS Inc v1i20 fluent fluent12 0 9 cortex src Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 client src 5 14 Release 12 0 ANSYS Inc January 26 2009 5 3 Compile a UDF Using the TUI Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 tgrid sre Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 multiport src srce udfexample c Microsoft R 32 bit C C Standard Compiler Version 13 10 3077 for 80x86 Copyright C Microsoft Corporation 1984 2002 All rights reserved udfexample c Generating udf_names c because of makefile udfexample obj cl c Za DUDF_EXPORTING Ic Program Files ANSYS Inc vi20 fluent fluent12 0 9 ntx86 2d Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 src Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 cortex src Ic Program Files ANSYS Inc v120 fluent fluent12 0 9 client src Ic Program Files ANSYS Inc v1i20 fluent fluent12 0 9 tgrid src Ic Program Files ANSYS Inc vi20 fluent fluent12 0 9 multiport src udf_names c Microsoft R 32 bit C C Standard Compiler Version 13 10 3077 for 80x86 Copyright C Microsoft Corporation 1984 2002 All rights reserved udf_names c Linking libudf dll because of makefile user_nt udf udf_names obj udfexample obj link Libpath c Program Files ANSYS Inc v120 fluent fluent12 0 9 ntx86 2d dll
236. POS p 1 P_POS p 2 Here the additional parameters P_INJ_ID P_INJECTION p and p gt part_id are re quired for the sorting in parallel but must be included whether you are using the serial or parallel version of ANSYS FLUENT The output written to the node specific file of these two parameters will be removed An example that utilizes these macros can be found in Section 2 5 8 DEFINE_DPM_OUTPUT Note that if you need to access other data such as cell values then for the parallel options except Shared Memory you will have access to all fluid and solver variables When you Release 12 0 ANSYS Inc January 26 2009 7 11 Parallel Considerations choose the Shared Memory option however you will have access only to the variables defined in the macros SV_DPM_LIST and SV_DPMS_LIST These macro definitions can be found in dpm h 7 5 Macros for Parallel UDFs This section contains macros that you can use to parallelize your serial UDF Where applicable definitions for these macros can be found in the referenced header file e g para h 7 5 1 Compiler Directives When converting a UDF to run in parallel some parts of the function may need to be done by the host and some by the compute nodes This distinction is made when the UDF is compiled By using ANSYS FLUENT provided compiler directives you can specify portions of your function to be assigned to the serial process the host or to the compute nodes The UDF that you
237. PROFILE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the appropriate boundary or cell zone condition dialog box in ANSYS FLUENT To open the boundary or cell zone condition dialog box select the zone in the Boundary Conditions or Cell Zone Conditions task page and click the Edit button gt Biren mecnchicnt or ERARE To hook the UDF select the name of your function in the appropriate drop down list For example if your UDF defines a velocity inlet boundary condition click the Momen tum tab in the Velocity Inlet dialog box Figure 6 2 17 select the function name e g x_velocity libudf from the X Velocity drop down list and click OK Note that the UDF name that is displayed in the drop down lists is preceded by the word udf e g udf x_velocity libudf Velocity Inlet Zone Name velocity inlet Momentum Thermal Radiation Species DPM Multiphase UDS Velocity Specification Method Components L Reference Frame Absolute Coordinate System Cartesian X Y 2 X velocity m s face x_velocity slibudF ae Y Velocity m s a constant Z Velocity m s constant Turbulence Specification Method Intensity and Hydraulic Diameter Turbulent Intensity 5 Hydraulic Diameter in 4 Figure 6 2 17 The Velocity Inlet Dialog Box 6 32 Release 12 0 ANSYS
238. R 0 5 user defined k constant 200 Figure 6 2 24 The Radiation Model Dialog Box Select Discrete Ordinates DO from the Model list and select Solar Ray Tracing in the Solar Load group box In the Illumination Parameters group box that appears select user defined from the Direct Solar Irradiation or Diffuse Solar Irradiation drop down list to open the User Defined Functions dialog box Figure 6 2 25 Release 12 0 ANSYS Inc January 26 2009 6 41 Hooking UDFs to ANSYS FLUENT User Defined Functions sol_diffuse_intensity libudf Figure 6 2 25 The User Defined Functions Dialog Box Select the function name e g sol_direct_intensity libudf from the list of UDFs displayed in the User Defined Functions dialog box and click OK The name of the function will subsequently be displayed under the selected property e g Direct Solar Irradiation in the Radiation Model dialog box Figure 6 2 24 See Section 2 3 18 DEFINE_SOLAR_INTENSITY for details about DEFINE_SOLAR_INTENSITY functions 6 2 19 Hooking DEFINE SOURCE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in a source term dialog box e g the Mass sources dialog box in ANSYS FLUENT To hook the UDF to ANSYS FLUENT you
239. R oo kkk kk kkk 24 24 24 24 24 2k include udf h DEFINE_VECTOR_EXCHANGE_PROPERTY custom_slip c mixture_thread second_column_phase_index first_column_phase_index vector_result real grav 2 0 9 81 real K 5 e4 real pgrad_x pgrad_y Thread pt st thread pointers for primary and secondary phases THREAD_SUB_THREAD mixture_thread second_column_phase_index THREAD_SUB_THREAD mixture_thread first_column_phase_index pt st at this point the phase threads are known for primary 0 and secondary 1 phases pgrad_x C_DP c mixture_thread 0 2 1 52 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros pgrad_y C_DP c mixture_thread 1 vector_result 0 pgrad_x K C_R c st C_R c pt K grav 0 vector_result 1 pgrad_y K C_R c st C_R c pt K grav 1 Note that the pressure gradient macro C_DP is now obsolete A more current pressure gradient macro can be found in Table 3 2 4 Hooking a Vector Exchange Property UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE VECTOR EXCHANGE PROPERTY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g custom_slip will become visible and selectable in the Phase Interaction dialog box in ANSYS FLUENT See Section 6 3 5 Hooking DEFINE_VECTOR
240. RANDTL_O name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_O name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the specific dissipation Prandtl number to the solver Example Specifying a Constant Specific Dissipation Prandtl Number include udf h DEFINE_PRANDTL_O user_pr_o c t real pr_o pr_o 2 return pr_o 2 68 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Hooking a Prandtl Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PRANDTL_O is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_o will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 14 Hooking DEFINE_PRANDTL UDFs for details DEF INE_PRANDTL_T Description You can use DEFINE_PRANDTL_T to specify Prandtl numbers that appear in the tempera ture equation diffusion term Usage DEFINE_PRANDTL_T name c t Argument Type Description symbol name UDF name cell_t c Index
241. RTY to specify a varying cell layering height when using the dynamic layering method to split or merge cells adjacent to a moving boundary The cell layering height can be specified as a function of time for general applications or as a function of crank angle for in cylinder applications Note that UDFs that are defined using DEFINE_DYNAMIC_ZONE_PROPERTY can only be executed as compiled UDFs For information on the dynamic layering method see Section 11 3 2 Dynamic Layering Method in the separate User s Guide Usage DEFINE_DYNAMIC_ZONE_PROPERTY name dt height Argument Type Description symbol name UDF name Dynamic_Thread dt Pointer to a structure that stores the dynamic mesh attributes real height Pointer to a real value layering height whose value will be varied in the UDF as a function of time or crank angle Function returns void There are three arguments to DEFINE_DYNAMIC_ZONE_PROPERTY name dt and height You supply name the name of the UDF and height the cell layering height to be assigned in the UDF as a function of time crank angle dt is a variable that is passed by the ANSYS FLUENT solver to your UDF In addition to the arguments listed previously you can utilize the variable in_cyl_ca_period and the macros DYNAMESH_CURRENT_TIME and TIME_TO_ABSOLUTE_CRANK_ANGLE time which are described as follows Variable Macro Description in_cyl_ca_period Crank angle period DYNAMESH_CURRENT_TIME Current dynamic
242. RW_FILE name and fp You supply name the name of the UDF fp is passed from the solver to the UDF DEFINE_RW_FILE cannot be used in UDFs that are executed on Windows systems Example The following C source code listing contains examples of functions that write information to a data file and read it back These functions are concatenated into a single source file that can be interpreted or compiled in ANSYS FLUENT ETT TTT tT CTT TCT TCT TCLrrCTrrCerrCrrrrerrrrrrerererrrrrrerrrrrererer eres 22 0 UDFs that increment a variable write it to a data file and read it back in FOO OR RR a a kK EEEE 2k 2k a ok 2k 2k ak ak ok ak ak include udf h int kount 0 define global variable kount Release 12 0 ANSYS Inc January 26 2009 2 23 DEFINE Macros DEFINE_ADJUST demo_calc d kount printf kount d n kount DEFINE_RW_FILE writer fp printf Writing UDF data to data file n fprintf fp d kount write out kount to data file DEFINE_RW_FILE reader fp printf Reading UDF data from data file n fscanf fp 4d amp kount read kount from data file At the top of the listing the integer kount is defined and initialized to zero The first function demo_calc is an ADJUST function that increments the value of kount at each iteration since the ADJUST function is called once per iteration See Sec tion 2 2 1 DEFINE ADJUST for more information about ADJUST functions
243. Returns CMUL c t cell t c Thread t laminar viscosity C_MU_T c t cell_t c Thread t turbulent viscosity C_MU_EFF c t cell_t c Thread t effective viscosity CKL c t cell_t c Thread t thermal conductivity turbulent thermal conductivity effective thermal conductivity laminar species diffusivity effective species diffusivity Table 3 2 15 Macros for Thermodynamic Properties Defined in mem h Name Arguments Argument Types Returns C_CP c t C_RGAS c t C_NUT c t cell _t c Thread t cell_t c Thread t cell _t c Thread t specific heat universal gas constant molecular weight turbulent viscosity for Spalart Allmaras Release 12 0 ANSYS Inc January 26 2009 3 19 Additional Macros for Writing UDFs Table 3 2 16 Additional Material Property Macros Defined in sg_mem h Macro Argument Types Returns C_FMEAN c t cell_t c Thread t primary mean mixture fraction C_FMEAN2 c t cell_t c Thread t secondary mean mixture fraction C_FVAR c t cell t c Thread t primary mixture fraction variance C_FVAR2 c t cell_t c Thread t secondary mixture fraction variance C_PREMIXC c t cell_t c Thread t reaction progress variable C LAM FLAME SPEED c t cell_t c Thread t laminar flame speed C_SCAT_COEFF c t cell_t c Thread t scattering coefficient C_ABS_COEFFF c t cell_t c Thread t absorption coefficient C_CRITICAL_STRAIN_ cell_t c Thread t critical strain r
244. S 2 1 56 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros FLUENT accommodates moving walls The function must be executed as a compiled UDF The function assumes an ideal reflection for the normal velocity component nor_coeff 1 while the tangential component is damped tan_coeff 0 3 First the angle of incidence is computed Next the normal particle velocity with respect to the wall is computed and subtracted from the particles velocity The reflection is complete after the reflected normal velocity is added The new particle velocity has to be stored in P_VELO to account for the change of particle velocity in the momentum balance for coupled flows The function returns PATH_ACTIVE for inert particles while it stops particles of all other types reflect boundary condition for inert particles include udf h DEFINE_DPM_BC bc_reflect p t f f_normal dim real alpha angle of particle path with face normal real vn 0 real nor_coeff real tan_coeff real normal 3 int i idim dim real NV_VEC x 1 55 0 3 if RP_2D dim is always 2 in 2D compilation Need special treatment for 2d axisymmetric and swirl flows if rp_axi_swirl real R sqrt P_POS p 1 P_POS p 1 P_POS p 2 P_POS p 2 if R gt 1 e 20 idim 3 normal 0 f_normal 0 normal 1 f_normal 1 P_POS p 1 R normal 2 f_normal 1 P_POS p 2 R else
245. S FLUENT data types are case sensitive When you use a UDF in ANSYS FLUENT your function can access solution variables at individual cells or cell faces in the fluid and boundary zones UDFs need to be passed appropriate arguments such as a thread reference i e pointer to a particular thread and the cell or face ID in order to allow individual cells or faces to be accessed Note that a face ID or cell ID by itself does not uniquely identify the face or cell A thread pointer is always required along with the ID to identify which thread the face or cell belongs to Some UDFs are passed the cell index variable c as an argument such as in DEFINE_PROPERTY my_function c t or the face index variable f such as in DEFINE_UDS_FLUX my_function f t i If the cell or face index variable e g cell_t c face_t f is not passed as an argument and is needed in the UDF the variable is always available to be used by the function after it has been declared locally See Sec tion 2 7 3 DEFINE_UDS_FLUX for an example The data structures that are passed to your UDF as pointers depend on the DEFINE macro you are using and the property or term you are trying to modify For example DEFINE_ADJUST UDFs are general purpose functions that are passed a domain pointer a such as in DEFINE_ADJUST my_function d DEFINE_PROFILE UDFs are passed a thread pointer t to the boundary zone that the function is hooked to such as in DEFINE_PROFILE my_function
246. SDOF_IYY 100 0 prop SDOF_1ZZ 100 0 printf nstage updated 6DOF properties Example 2 The following UDF named delta_missile specifies case injector forces and moments that are time dependent Specifically the external forces and moments depend on the current angular orientation of the moving object Note that this UDF must be executed as a compiled UDF DOR OO 2K KK FK 2K K FK 2K KK FK 2K 2K I 2K a RK 2K aK 2K 2K 2 ak SDOF property compiled UDF with external forces moments BE o oo oo kk kk ACA A A kkk k k kkk include udf h DEFINE_SDOF_PROPERTIES delta_missile prop dt time dtime prop SDOF_MASS 907 185 prop SDOF_IXX 27 116 prop SDOF_IYY 488 094 prop SDOF_1ZZ 488 094 add injector forces moments register real dfront fabs DT_CG adt 2 Release 12 0 ANSYS Inc January 26 2009 2 223 DEFINE Macros 0 179832 DT_THETA dt 1 register real dback fabs DT_CG dt 2 0 329184 DT_THETA dt 1 if dfront lt 0 100584 prop SDOF_LOAD_F_Z prop SDOF_LOAD_M_Y 10676 0 1920 0 if dback lt 0 100584 prop SDOF_LOAD_F_Z 42703 0 prop SDOF_LOAD_M_Y 14057 0 t printf ndelta_missile updated 6DOF properties Hooking a DEFINE_SDOF_PROPERTIES UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SDOF_PROPERTIES is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs
247. SOURCE DEFINE_SOURCE DEF INE_SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE_PROFILE DEFINE PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s phase dependent secondary phase s mixture primary and secondary phase s primary and secondary phase s Release 12 0 ANSYS Inc January 26 2009 C 3 Eulerian Model Laminar Flow Table C 3 2 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Boundary Conditions Fluid species mass fraction granular temperature porosity user defined scalar viscous resistance inertial resistance DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE phase dependent secondary phase s mixture mixture primary and secondary phase s primary and secondary phase s Wall species boundary condition shear stress components moving velocity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature user defined scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_DPM_BC phase dependent primary and secondary phase s second
248. SOURCE term UDF all the necessary variables it needs to define a custom source term since source terms are solved on a cell basis Consequently your UDF will not need to loop over cells in the thread since ANSYS FLUENT is already doing it The units on all source terms are of the form generation rate volume For example a source term for the continuity equation would have units of kg m s Example 1 Source Term Addition The following UDF named xmom_source is used to add source terms in ANSYS FLUENT The source code can be interpreted or compiled The function generates an z momentum source term that varies with y position as source 0 5C2py vz Vx Suppose source S Alv vz where A 0 5C2py Release 12 0 ANSYS Inc January 26 2009 2 1 01 DEFINE Macros Then dS d S2 Alve Ave loal The source term returned is source Alv vz and the derivative of the source term with respect to v true for both positive and negative values of v is ds 22 Se oA duz PERO CCAR AAR I IR oo kkk kkk kkk k kkk UDF for specifying an x momentum source term in a spatially dependent porous media eect t ttt ttt ooo rec rorerrrrrerrrrrrr ss y include udf h define C2 100 0 DEFINE_SOURCE xmom_source c t dS eqn real x ND_ND real con source C_CENTROID x c t con C2 0 5 C_R c t x 1 source con fabs C_U c t C_U c t dS eqn 2 con fabs C_U c t return source 2
249. SUPER_THREAD 3 68 THREAD TO 2 115 2 117 2 219 2 232 3 27 THREAD_T1 2 232 3 27 THREAD_TYPE 2 156 threads 1 9 cell 1 10 face 1 10 fluid checking 3 81 node 1 10 phase level 1 17 3 66 pointers 3 29 3 66 referencing 1 17 subthreads 1 17 superthreads 1 17 variables and neighboring cell variables 1 8 Time Step Size 8 21 time stepping control for DPM 2 202 time dependent variables 3 74 time stepping control UDFs 2 7 TIME_TO_ABSOLUTE_CRANK_ANGLE 3 43 total emissivity equation 2 42 Tracked_Particle 2 186 3 36 transient pressure UDF example 8 19 transition correlation UDFs 2 118 transition length function UDF 2 118 transition onset momentum thickness Reynolds number UDFs 2 120 transport equations custom source for 2 100 trigonometric functions A 13 Index 16 tube flow 8 19 turbulence kinetic energy Prandtl number UDFs 2 65 turbulent dissipation UDFs 2 64 turbulent Schmidt number UDFs 2 124 turbulent viscosity UDFs 2 125 Prandtl number udf bat 5 4 udf h file 1 5 4 2 5 3 location of 4 2 5 3 udf h header file including 1 5 UDFs about 1 1 arguments 1 11 arguments not passed 1 11 calling sequence of 1 12 compilation environment 5 4 compiled 1 6 5 5 data structures 1 10 1 17 data types 1 10 defining using DEFINE macros 1 4 2 1 definition of 1 1 examples 8 1 boundary condition 8 14 detailed 8 13 property 8 30 reaction rate 8 35 source terms
250. SV_P SV_NULL EXCHANGE_SVAR_FACE_MESSAGE is rarely needed in UDFs You can exchange multiple storage variables between compute nodes Storage variable names are separated by com mas in the argument list and the list is ended by SV_NULL For example EXCHANGE_SVAR_MESSAGE domain SV_P SV_T SV_NULL is used to exchange cell pres sure and temperature variables You can determine a storage variable name from the header file that contains the variable s definition statement For example suppose you want to exchange the cell pressure C_P with an adjacent compute node You can look at the header file that contains the definition of C P mem h and determine that the storage variable for cell pressure is SV_P You will need to pass the storage variable to the exchange macro 7 6 Limitations of Parallel UDFs The macro PRINCIPAL_FACE_P can be used only in compiled UDFs PRF_GRSUM1 and similar global reduction macros Section 7 5 4 Global Reduction Macros cannot be used in DEFINE_SOURCE UDFs in parallel ANSYS FLUENT As a workaround you can write a DEFINE_ADJUST UDF that calculates a global sum value in the adjust function and then save the variable in user defined memory You can subsequently retrieve the stored variable from user defined memory and use it inside a DEFINE_SOURCE UDF This is demonstrated below In the following example the spark volume is calculated in the DEFINE_ADJUST function and the value is stored in user defined
251. SYS FLUENT 7 1 7 1 1 Command Transfer and Communication 7 4 7 2 Cells and Faces in a Partitioned Mesh 4 7 7 Release 12 0 ANSYS Inc January 26 2009 CONTENTS ta Parallelizing Your Serial UDP s epa eae de ee Soe eR oe eS 7 9 7 4 Parallelization of Discrete Phase Model DPM UDFs 7 11 7 5 Macros for Parallel UDFS 22 26 2645 2 dG eee EDR eee 7 12 Tol Compiler Directives scssi eee pa ed ee eh eee a 4 7 12 7 5 2 Communicating Between the Host and Node Processes 7 15 foo Predicates occse sputas pu REED ES ARE ESSER ERS 7 17 tee Global Reduction Macros sunk a6 4 eed a Oe eae EN wo 7 18 foo Looping Macros se s ne eek ee ee p eb eu Re e eh 7 22 T 5 6 Cell amd Face Partition ID Macros s eoo dor secang tans 7 26 7 5 7 Message Displaying Macros oaoa 7 28 7 5 8 Message Passing Macros isd ieee ee bee eda e ate ds 7 29 7 5 9 Macros for Exchanging Data Between Compute Nodes 7 33 T6 Limitations of Parallel WDFs i432 4444 te 24 bee 4464S ue ew S 7 33 tt Process Ieniies rom 2 acu so eee ls ee he eg de ego He me 1 7 35 Te Paralel UDF Example p egri ep Sa ee a Pee CE we Al Se eS 7 37 ta Wiitmg Filesin Parallel s s m 64 44 3804 ce be kaen ee eases x 7 40 Examples 8 1 8 1 Step By Step UDF Example s 2 42544 a e 24 b 6 Yee eS eS 8 1 el Process Overview sas de ata eee Be toii we OK pa ga 8 1 8 1 2 Step 1 Define Your Problem 4 24444 446 a 8 2 8 1 3 Ste
252. See Section 2 3 9 DEFINE_HEAT_FLUX for details about DEFINE_HEAT_FLUX functions 6 24 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 10 Hooking DEFINE_IGNITE_SOURCE UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE_IGNITE_SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 12 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first open the General task page 2 Select Pressure Based from the Type list and select Transient from the Time list Then select a turbulence model in the Viscous Model dialog box RR MANE Edit Next set up an appropriate reaction model in the Species Model dialog box RA A Edit Select either the Premixed Combustion or the Partially Premixed Combustion model in the Species Model dialog box and click OK Then open the Autoignition Model dialog box RRA A Edit Select the Knock Model from the Model list in the Autoignition Model dialog box and click OK Next open the User Defined Function Hooks dialog box Figure 6 2 12 Release 12 0 ANSYS Inc January 26 2009 6 25 Hooking UDFs to ANSYS FLUENT Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at E
253. Select user defined in the drop down list for one of the properties e g Particle Emissivity in the Create Edit Materials dialog box in order to open the User Defined Functions dialog box Figure 6 4 10 Release 12 0 ANSYS Inc January 26 2009 6 73 Hooking UDFs to ANSYS FLUENT i In order for the Particle Emissivity property to be displayed in the sample dialog box shown above you must enable a radiation model turn on the Particle Radiation Interaction option in the Discrete Phase Model dialog box and introduce a particle injection in the Injections dialog box User Defined Fu ity libudF coal_scattering libudf Figure 6 4 10 The User Defined Functions Dialog Box Select the function name e g coal_emissivity libudf from the list of UDFs displayed in the User Defined Functions dialog box and click OK The name of the function will subsequently be displayed under the selected property e g Particle Emissivity in the Create Edit Materials dialog box See Section 2 3 16 DEFINE PROPERTY UDFs for details about DEFINE DPM PROPERTY func tions 6 74 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 10 Hooking DEFINE_DPM_SCALAR_UPDATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SCALAR_UPDATE UDF the name of the function you sup plied as a DEFINE macro argument wi
254. Step in the drop down list under Get Data Every Next select Area Weighted Average from the Report Type drop down list In the drop down lists under Field Variable select Pressure and Static Pressure Finally select pressure outlet 5 in the Surfaces selection list and click OK In a similar manner you can set up a second monitor to capture the velocity magnitude fluctuations in the pressure outlet 8 22 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples After the first time step has been completed the monitors should appear in the chosen plot windows Alternatively you can read the files by opening the File XY Plot dialog box Figure 8 2 10 Boa HA Set up File XY Plot Plot Title Legend Title Convergence history of Static Pressure on pressure 4rea Weighted Average Static Pre Files _ _ Legend Entries Tutorials monitor 1 out Convergence history of Static Pressi Tutorials monitor 1 out e on pressure outlet 5 in SI units Change Legend Entry Cases Gr Coe Ceo Figure 8 2 10 The File XY Plot Dialog Box You can read an output file by clicking Add and selecting it in the Select File dialog box that opens and clicking OK Then click the Plot button in the File XY Plot dialog box to obtain plots like those shown in Figures 8 2 11 and 8 2 12 Figure 8 2 11 nicely illustrates that
255. TY_WEIGHTING_FACTOR for details about defining DEFINE_EMISSIVITY_WEIGHTING_FACTOR UDFs 6 2 8 Hooking DEFINE_GRAY_BAND_ABS_COEFF UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_GRAY_BAND_ABS_COEFF UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the Create Edit Materials dialog box in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first make sure that the Discrete Ordinates DO model is selected in the Radiation Model dialog box with a nonzero Number of Bands in the Non Gray Model group box Then open the Materials task page lt DEIGEN Select the appropriate material from the Material selection list and click the Create Edit button to open the Create Edit Materials dialog box Figure 6 2 10 Create Edit Materials Name Order Materials by air Material Type Fluid x Name Chemical Formula Chemical Formula FLUENT Fluid Materials air v L FLUENT Database f User Defined Database Properties 0 0242 Viscosity kg m s 1 7894e 05 Absorption Coefficient 1 m A epeae user_gray_band_abs libudf Scattering Coefficient 1 m ooo soe Scattering Phase Function isotropic J M Figure 6 2 10 The Create Edit Materials Dialog Box Next select user defined gray band from the Absorption Coefficient dr
256. T_PHASE_FUNC name cosine and f You supply name the name of the UDF cosine and f are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the real fraction of radiation energy scattered from direction 7 to direction j and return it to the solver Note that the solver computes and stores a scattering matrix for each material by calling this function for each unique pair of discrete ordinates Example In the following example a number of UDFs are concatenated in a single C source file These UDFs implement backward and forward scattering phase functions that are cited by Jendoubi et al 5 The source code can be interpreted or compiled in ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 2 95 DEFINE Macros peaa ooo oo kkk A A 1 1 1 21 kkk kkk kkk kk k kkk UDFs that implement backward and forward scattering phase functions as cited by Jendoubi et al EEEE ooo oo kkk kkk kk kkk kkk include udf h DEFINE_SCAT_PHASE_FUNC ScatPhiB2 c fsf real phi 0 fsf 0 phi 1 0 1 2 c 0 25 3 c c 1 return phi DEFINE_SCAT_PHASE_FUNC ScatPhiB1 c fsf real phi 0 fsf 0 phi 1 0 0 56524 c 0 29783 0 5 3 c c 1 0 08571 0 5 5 c c c 3 c 0 01003 8 35 c c C C 30 C C 3 0 00063 8 63 cxcxcxcxc 70 xcxcxc 15 c return phi DEFINE_SCAT_PHASE_FUNC ScatPhiF3 c fsf real phi 0 fsf 0 phi 1 0 1 2 c 0 25 3 c c 1 return phi
257. T_VECT tan_1 tan_1 V_CROSS tan_1 normal tan_2 beta is calculated by neglecting the coth alpha term in the paper it is approximately right beta MAX M_PI sqrt sin alpha 1 0 sin alpha DPM_SMALL phi M_PI betaxlog 1 0 cheap_uniform_random 1 0 exp beta if cheap_uniform_random gt 0 5 phi phi vnew vmag cp cos phi sp sin phi for i 0 i lt idim i P_VEL p i vnew tan_1 i cp tan_2 i l sp face_vel i Subtract off from the original state for i 0 i lt idim i P_VELO p i P_VEL p i if DPM_STOCHASTIC_P P_INJECTION p Reflect turbulent fluctuations also Compute normal velocity dum 0 for i 0 i lt idim i 2 1 62 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros dum p gt V_prime i normal i Subtract off normal velocity for i 0 i lt idim i p gt V_prime i 2 dum normal i return PATH_ACTIVE Hooking a DPM Boundary Condition UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_BC is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the ap propriate boundary condition dialog box e g the Velocity Inlet dialog box in ANSYS FLUENT See Section 6 4 1 Hooking DEFINE D
258. The following is ONLY valid for 2d axisymmetric calculations Additional effort is necessary because DPM tracking is done in THREE dimensions for TWO dimensional axisymmetric calculations P_POS p 1 Radial location vector P_POS p 2 Y and Z in O and 1 radi_pos 0 radi_pos 1 radius NV_MAG radi_pos NV_VS radi_pos radi_pos radius Normalized radius direction vector imp_vel 0 P_VEL p 0 Axial particle velocity component imp_vel 1 NVD_DOT radi_pos P_VEL p 1 P_VEL p 2 0 Dot product of normalized radius vector and y amp z components of particle velocity vector gives _radial_ particle velocity component vel_ortho NV_DOT imp_vel normal velocity orthogonal to wall if vel_ortho lt MIN_IMPACT_VELO See above MIN_IMPACT_VELO return if UDM_checked We will need some UDMs if check_for_UDM so check for their availability return Using int variable for speed could even just call check_for UDFM c0 F_CO f t tO THREAD_TO t num_in_data F_UDMI f t NUM_OF_HITS Average diameter of particles that hit the particular wall face F_UDMI t AVG_DIAMETER P_DIAM p Release 12 0 ANSYS Inc January 26 2009 2 1 71 DEFINE Macros num_in_data F_UDMI f t AVG_DIAMETER num_in_data 1 C_UDMI c0 t0 AVG_DIAMETER F_UDMI f t AVG_DIAMETER
259. UDF require the use of a C compiler that is native to the operating system and machine you are running on Most UNIX operating systems provide a C compiler as a standard feature If you are operating on a Windows system you will need to ensure that a Microsoft Visual Studio is installed on your machine before you proceed If you are unsure about compiler requirements for your system please contact ANSYS FLUENT installation support For Linux machines ANSYS FLUENT supports any ANSI compliant compiler Obsolete versions of any native compiler may not work properly with com piled UDFs When launching ANSYS FLUENT on Windows using FLUENT Launcher the UDF Compiler tab Figure 5 1 1 allows you to specify compiler settings for compiling UDFs Fal FLUENT Launcher Dimension Options 3 C Double Precision O 2 O Use Microsoft Job Scheduler Display Options Processing Options Display Mesh After Reading Serial Embed Graphics Windows Parallel Workbench Color Scheme lt lt Show Less General Options Parallel Settings Scheduler UDF Compiler Environment Setup Compilation Environment for UDF Win 32 C Program Files ANSYS Inc w120 fluent ntbinntx86 udf bat w Figure 5 1 1 The UDF Compiler Tab of the FLUENT Launcher Dialog Box The Setup Compilation Environment for UDF option is enabled by default and allows you to specify a batch file that contains UDF compilation environment settings Enter a batch file name and
260. UENT whenever the case is subsequently read If you do not want the shared library saved with your case file then you must remember to load it into ANSYS FLUENT using the Compiled UDFs dialog box or the UDF Library Manager dialog box in subsequent sessions Release 12 0 ANSYS Inc January 26 2009 5 9 Compiling UDFs 5 3 Compile a UDF Using the TUI The first step in compiling a UDF source file using the text user interface TUI involves setting up the folder structure where the shared compiled library will reside for each of the versions of ANSYS FLUENT you wish to run e g 2d 3d You will then modify the file named makefile to setup source file parameters Subsequently you will execute the Makefile which compiles the source file and builds the shared library from the resulting object files Finally you will load the UDF library into ANSYS FLUENT Using the TUI option allows you the added advantage of building a shared library for precompiled object file s that are derived from non ANSYS FLUENT sources e g o objects from f sources See Section 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources for details Note that if you are running serial or parallel ANSYS FLUENT on a Win dows system and intend to compile a UDF then you must have Microsoft Visual Studio installed on your machine preferably on the C drive 5 3 1 Set Up the Directory Structure The folder directory structures for Windows systems
261. US TIME or PREVIOUS 2 TIME macros since it is not included in udf h 3 74 Release 12 0 ANSYS Inc January 26 2009 3 5 Time Dependent Macros i N_ITER can only be utilized in compiled UDFs Some time dependent variables such as current physical flow time can be accessed directly using a solver macro CURRENT_TIME or indirectly by means of the RP variable macro RP_Get_Real flow time These two methods are shown below Solver Macro Usage real current_time current_time CURRENT_TIME Equivalent RP Macro Usage real current_time current_time RP_Get_Real flow time Table 3 5 2 shows the correspondence between solver and RP macros that access the same time dependent variables Table 3 5 2 Solver and RP Macros that Access the Same Time Dependent Variable Solver Macro Equivalent RP Variable Macro CURRENT_TIME RP_Get_Real flow time CURRENT_TIMESTEP RP_Get_Real physical time step N_TIME RP_Get_Integer time step Fa You should not access a scheme variable using any of the RP_GET_ func tions from inside a cell or face looping macro c_loop or f loop This type of communication between the solver and cortex is very time consuming and therefore should be done outside of loops Release 12 0 ANSYS Inc January 26 2009 3 75 Additional Macros for Writing UDFs Example The integer time step count accessed using N_TIME is useful in DEFINE_ADJUST functions fo
262. User Object files for example o files from f sources USER_OBJECTS 5 16 Release 12 0 ANSYS Inc January 26 2009 5 3 Compile a UDF Using the TUI aera ena leans ieee oi elena aaa een ee ra Build targets do not modify below this line e SSS Se SS SS se SS Ss SSeS SSS a SaaS SSeS ees eee Note that in the previous example path represents the directory where you installed ANSYS FLUENT 3 In your library directory e g libudf execute the Makefile by typing a command that begins with make and includes the architecture of the machine you will run ANSYS FLUENT on which you identified in a previous step For example for the Linux 1nx86 architecture type make FLUENT_ARCH 1nx86 ANSYS FLUENT will build a shared library for each version you created a directory for Section 5 3 1 Set Up the Directory Structure and will display messages about the compile build process in the console You can view the compilation history in the log file that is saved in your working directory For example when compiling building a shared library for a source file named profile c and a UDF library named libudf on a Linux architecture the console messages may include the following Working for d in 1nx86 23 do CN cd d for f in src ch src makefile do if f basename f then echo linking to f in d In s f fi done echo n echo building library in
263. VITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_dom_diff_ref1 will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 37 DEFINE Macros 2 3 5 DEFINE_DOM_SOURCE Description You can use DEFINE DOM_SOURCE to modify the emission term first term on the right hand side in Equation 5 3 37 or Equation 5 3 38 in the separate Theory Guide as well as the scattering term second term on the right hand side of either equation in the radiative transport equation for the discrete ordinates DO model Usage DEFINE DOM SOURCE name c t ni nb emission in scattering abs coeff scat_coeff Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread int ni Direction represented by the solid angle int nb Band number needed for the non gray discrete ordinates DO model real emission Pointer to emission term in the radiative transport equation Equation 5 3 37 in the separate Theory Guide real in_scattering Pointer to scattering term in the radiative transport equation Equation 5 3 38 in the separate Theory Guide real abs_coeff Pointer to absorption coefficient real scat_coeff Pointer to
264. X v 0 230 0 5 NV_VV rvec NODE_COORD v origin NV_CROSS dx omega rvec NV_S dx dtime NV_V NODE_COORD v dx J end_f_loop f tf Hooking a DEFINE_GRID_MOTION to ANSYS FLUENT After the UDF that you have defined using DEFINE_GRID_MOTION is compiled Chap ter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Dynamic Mesh Zones dialog box in ANSYS FLUENT See Section 6 5 4 Hooking DEFINE GRID MOTION UDFs for details on how to hook your DEFINE_GRID_MOTION UDF to ANSYS FLUENT 2 220 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros 2 6 5 DEFINE_SDOF_PROPERTIES Description You can use DEFINE SDOF PROPERTIES to specify custom properties of moving objects for the six degrees of freedom SDOF solver in ANSYS FLUENT These include mass moment and products of inertia and external forces and moment properties The properties of an object which can consist of multiple zones can change in time if de sired External load forces and moments can either be specified as global coordinates or body coordinates In addition you can specify custom transformation matrices using DEFINE SDOF PROPERTIES Usage DEFINE_SDOF_PROPERTIES name properties dt time dtime Argument Type Description symbol name UDF name real properties Pointer to the array that stores the SDOF properties Dynamic_Thread dt Po
265. XC_T c t real P C_P c t real ipv C_IGNITE c t if c 0 dt CURRENT_TIMESTEP p_op RP_Get_Real operating pressure A1 A pow 0_N 100 0_E 2 48 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros if ipv gt 1 0 lit TRUE P p_op P 101325 in atm P MAX P 0 01 minimum pressure for ignition if fuel gt 0 99 lit time A1 pow P P_E exp Ea T if time gt 0 0 real max_source rho 5 0 ipv dt real user_source rho time source MIN user_source max_source else source 0 0 return Hooking an Ignition Source UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_IGNITE_SOURCE is compiled Chap ter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g ign udf_src will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 10 Hooking DEFINE IGNITE SOURCE UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 49 DEFINE Macros 2 3 11 DEFINE_NET_REACTION_RATE Description You can use DEFINE NET REACTION RATE to compute the homogeneous net molar reaction rates of all species The net reaction rate of a species is the sum over all reactions of the volumetric reaction rates where R is the net reaction rate of species i and Rir is the Arrhenius molar rate of creation destructio
266. YS Inc January 26 2009 2 1 33 DEFINE Macros pE aaao o oo o kkk kk A A kkk kkk kkk kkk kkk kkk User defined wall functions separated into turbulent and laminar regimes pE aaao ooo kkk k kkk 4 242k kk include udf h DEFINE_WALL_FUNCTIONS user_log_law f t c0 tO wf_ret yPlus Emod real wf_value switch wf_ret case UPLUS_LAM wf_value yPlus break case UPLUS_TRB wf_value log Emod yPlus KAPPA break case DUPLUS_LAM wf_value 1 0 break case DUPLUS_TRB wf_value 1 KAPPA yPlus break case D2UPLUS_TRB wf_value 1 KAPPA yPlus yPlus break default printf Wall function return value unavailable n return wf_value Hooking a Wall Function UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE WALL FUNCTIONS is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_log_law will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 28 Hooking DEFINE WALL FUNCTIONS UDFs for details 2 1 34 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros 2 4 Multiphase DEFINE Macros The DEFINE macros presented in this section are used for multiphase applications only Table 2 4 1 provides a quick reference guide to the multiphase specific DEFINE macros the functions
267. _EXCHANGE_PROPERTY UDF s for details Release 12 0 ANSYS Inc January 26 2009 2 1 53 DEFINE Macros 2 5 Discrete Phase Model DPM DEFINE Macros This section contains descriptions of DEFINE macros for the discrete phase model DPM Table 2 5 1 provides a quick reference guide to the DPM DEFINE macros the functions they define and the dialog boxes where they are activated in ANSYS FLUENT Definitions of each DEFINE macro are contained in the udf h header file For your convenience they are listed in Appendix B e Section 2 5 1 e Section 2 5 2 e Section 2 5 3 e Section 2 5 4 e Section 2 5 5 e Section 2 5 6 e Section 2 5 7 e Section 2 5 8 e Section 2 5 9 e Section 2 5 10 e Section 2 5 11 e Section 2 5 12 e Section 2 5 13 e Section 2 5 14 e Section 2 5 15 2 154 DEF INE_DPM_BC DEFINE DPM BODY FORCE DEFINE DPM DRAG DEF INE_DPM_EROSION DEF INE_DPM_HEAT_MASS DEFINE DPM_INJECTION_INIT DEF INE_DPM_LAW DEF INE_DPM_OUTPUT DEFINE DPM PROPERTY DEF INE_DPM_SCALAR_UPDATE DEFINE_DPM_SOURCE DEFINE DPM SPRAY COLLIDE DEFINE DPM SWITCH DEF INE_DPM_TIMESTEP DEF INE_DPM_VP_EQUILIB Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros Table 2 5 1 Quick Reference Guide for DPM Specific DEFINE Macros Function DEFINE Macro Dialog Box Activated In particle state at boundaries body forces on particles drag coefficients between partic
268. _coeff 0 0 scattering coefficient static real las_coeff 0 0 linear anisotropic scattering coefficient static real epsilon_w 1 0 wall emissivity DEFINE_ADJUST p1_adjust domain Make sure there are enough user defined scalars if n_uds lt N_REQUIRED_UDS Internal_Error not enough user defined scalars allocated DEFINE_SOURCE energy_source c t dS eqn dS eqn 16 xabs_coeff xSIGMA_SBC pow C_T c t 3 return abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 DEFINE_SOURCE p1_source c t dS eqn dS eqn 16 xabs_coeff SIGMA_SBC pow C_T c t 3 return abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 DEFINE_DIFFUSIVITY p1_diffusivity c t i return 1 3 abs_coeff 3 las_coeff scat_coeff DEFINE_PROFILE p1_bc thread position face_t f real A ND_ND At real dG ND_ND drO ND_ND es ND_ND ds A_by_es real aterm alpha0 beta0 gamma0 Gsource Ibw real Ew epsilon_w 2 2 epsilon_w Thread t0 thread gt t0 8 46 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Do nothing if areas aren t computed yet or not next to fluid if Data_Valid_P FLUID_THREAD_P t0 return begin_f_loop f thread 4 cell_t c0 F_CO f thread BOUNDARY_FACE_GEOMETRY f thread A ds es A_by_es dr0 At NV_MAG A if NULLP T_STORAGE_R_NV t0O SV_UDSI_G P1 Gsource 0
269. _mw double yil double MW sum 0 0 int i for i 0 i lt n_specs i sum yili mwli MW 1 0 MAX sum SMLL return MW Kg Kmol double MIXTURE_density double temp double P double yi double den 0 0 int i for i 0 i lt n_specs i if yi i gt SMLL den yili RKEOS_spvol temp P i return 1 den Kg m73 8 80 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double MIXTURE_specific_heat double temp double density double P double yi double cp 0 0 int i for i 0 i lt n_specs i if yi i gt SMLL cp yili RKEOS_specific_heat temp mw i density MIXTURE_mvw yi i return cp J Kg K double MIXTURE_enthalpy double temp double density double P double yi double h 0 0 int i for i 0 i lt n_specs i if yili gt SMLL h yili RKEOS_enthalpy temp mw li density MIXTURE_mw yi i return h J Kg double MIXTURE_enthalpy_prime double temp double density double P i double yi double hi double h 0 0 int i for i 0 i lt n_specs i hi i hf i mw i RKEOS_enthalpy temp mw i density MIXTURE_mw yi if ai SMLL h yili hfli mw i RKEOS_enthalpy temp mw i density MIXTURE_mw yi i return h J Kg Release 12 0 ANSYS Inc January 26 2009 8 81 Examples double MIXTURE_entropy double te
270. a real PI 3 141592 cos_theta NV_DOT ray_direction en angle acos cos_theta if angle gt 45 amp amp angle lt 60 specular_reflectivity 0 3 specular_transmissivity 0 T Hooking a Discrete Ordinates Model DOM Specular Reflectivity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DOM_SPECULAR REFLECTIVITY is in terpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_dom_spec_refl will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 6 Hooking DEFINE_DOM_SPECULAR_REFLECTIVITY UDFs for details 2 3 7 DEFINE_EMISSIVITY_WEIGHTING_FACTOR Description When employing the non gray discrete ordinates DO radiation model you can use DEFINE EMISSIVITY WEIGHTING FACTOR to modify the emissivity weighting factor F 0 gt n T F 0 gt n T By default the emissivity weighting factor is calculated internally by ANSYS FLUENT so it can be used in the emission term of the radiative transfer equation as shown in Equation 5 3 39 in the separate Theory Guide This macro allows you to revise the calculated value Release 12 0 ANSYS Inc January 26 2009 2 41 DEFINE Macros Usage DEFINE EMISSIVITY WEIGHTING FACTOR name c t T nb emissivity weighting factor Argument Type Description symbol name UDF
271. a field It then computes a tempera ture function f Tmin f T 7 Tmax Tmin and stores it in user defined memory location 0 which is allocated as described in Sec tion 3 2 3 Cell Macros After you hook the on demand UDF as described in Sec tion 6 1 6 Hooking DEFINE_ON_DEMAND UDFSs the field values for f T will be available in drop down lists in postprocessing dialog boxes in ANSYS FLUENT You can select this field by choosing User Memory 0 in the User Defined Memory category If you write a data file after executing the UDF the user defined memory field will be saved to the data file This source code can be interpreted or compiled in ANSYS FLUENT 2 20 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros paaa o k kkk kk kkk kkk kkk kkk kk kk kk kkk k k kkk kkk k 4 4 4 k UDF to calculate temperature field function and store in user defined memory Also print min max avg temperatures BO ooo oo k kkk k kkk kkk kk kk include udf h DEFINE_ON_DEMAND on_demand_calc Domain d declare domain pointer since it is not passed as an argument to the DEFINE macro real tavg 0 real tmax 0 real tmin 0 real temp volume vol_tot Thread t cell_t c d Get_Domain 1 Get the domain using ANSYS FLUENT utility Loop over all cell threads in the domain thread_loop_c t d Compute max min volume averaged temperature Loop over all cells
272. a i 0 475 xomega i omega i void Omega acentric factor x omega 0 0 348 H20 omega 1 0 007 CH4 omega 2 0 021 02 omega 3 0 225 CO2 omegal4 0 040 N2 void Hform formation enthalpy J Kgmol hf 0 2 418379e 08 H20 hf 1 74895176 CH4 hf 2 0 02 hf 3 3 9353235e 08 C02 hf 4 0 N2 void Cp_Parameters coefficients of specific heat polynomials J Kg K cp 0 0 1609 791 H20 cp 1 0 0 740494 cp 2 0 9 129835e 06 cp 3 0 3 813924e 08 cp 4 0 4 80227e 12 cp 0 1 872 4671 CH4 cp 1 1 5 305473 cp 2 1 0 002008295 cp 3 1 3 516646e 07 cp 4 1 2 33391e 11 cp 0 2 811 1803 02 cp 1 2 0 4108345 cpl2 2 0 0001750725 8 86 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples cp 3 2 cp 4 2 3 757596e 08 2 973548e 12 cp 0 3 453 577 CO2 cp 1 3 1 65014 cp 2 3 1 24814e 3 cp 3 3 3 78201e 7 cp 4 3 0 cp 0 4 938 8992 N2 cp 1 4 0 3017911 cp 2 4 8 109228e 05 cp 3 4 8 263892e 09 cp 4 4 1 537235e 13 peaa oo ooo oo kk kkk kkk kkk kkk User Defined Function Redlich Kwong Equation of State for Real Gas Modeling Author Frank Kelecy Date
273. a variable in a boundary conditions dialog box through the graphical user interface This index is subsequently passed to your UDF by the ANSYS FLUENT solver so that your function knows which variable to operate on Function returns void There are three arguments to DEFINE_PROFILE name t and i You supply name the name of the UDF t and i are variables that are passed by the ANSYS FLUENT solver to your UDF While DEFINE_PROFILE is usually used to specify a profile condition on a boundary face zone it can also be used to specify or fix flow variables that are held constant during computation in a cell zone See Section 7 2 4 Fixing the Values of Variables in the separate User s Guide for more information on fixing values in a cell zone boundary condition For these cases the arguments of the macro will change accordingly Note that unlike source term and property UDFs profile UDFs defined using DEFINE_PROFILE are not called by ANSYS FLUENT from within a loop on threads in the boundary zone The solver passes only the pointer to the thread associated with the boundary zone to the DEFINE PROFILE macro Your UDF will need to do the work of looping over all of the faces in the thread computing the face value for the boundary variable and then storing the value in memory ANSYS FLUENT has provided you with a face looping macro to loop over all faces in a thread begin_f_loop See Chap ter 3 Additional Macros for Writing UDFs for d
274. aaa a 2 25 Zad DEFINE CHEM STEP spe sie goat hak a a ea eo a ea ewe a 2 31 Yio DEFINE GPHI o euge 4 bee ee a e e RR em GS 2 33 23 0 DEFINEZDIFFUSIVITY se a pd 4464 48844445 652489 444 2 34 204 DEFINE DOM DIFFUSE REFLECTIVITY 2 04 eni ea a ww a eo 2 36 2 35 90 DEFINE DOM SOURCE o i tes e Bada ea wed oo Reda aE aS 2 38 2 3 6 DEFINE_DOM_SPECULAR_REFLECTIVITY 2 39 2 3 7 DEFINE EMISSIVITY WEIGHTING FACTOR 2 41 2 3 8 DEFINE_GRAY_BAND_ABS_COEFF 5 5 0084 2 43 Zoo DEFINE HEAT FEUX lt lt 4 ou a oh ok ace GY ace Bae ee ee a 2 45 23 00 DEFINEAGNITE SOURGE c e s s a 844 mee A meee we ad 2 47 2 3 11 DEFINE NET REACTION RATE 2 50 229 12 DEFINE NOX RATE necedi era ee e Bae a e A a i 2 52 29 15 DEFINE PR RATE o e cioe gp eosi 26 hak Bd heh eg E 2 58 Zod DEFINE PRANDTL UDES 2444 4464544460 644 26 445 2 64 Zoo DEPINE PROPILE oce poa 44045 bce ac Sea eo AG es ae 2 72 2 3 6 DEPINE PROPERTY UDES o y ecim ie 4a amp eee ee ee Gee a 2 87 23 17 DEPINE SCAT PHASE FUNG ci 454484 GYR wk CMA RE EE 2 95 2 3 18 DEFINE SOLAR INTENSITY 2 98 2 5 19 DEFINE SOURCE o cc ssa ee het dee eed ee Re aS 2 100 23 00 DEPONE SOX RATE sai su s gue boa e SR SES Se ES 2 106 20 21 DEFINE SPECIFIC HEAT 2 4 44s 46424 teh EGR H RH a 2 113 Zee DEFINE ORRADRE 204 3 ce ow a eo J eh ey woe oh ee ia 2 114 23 29 DEFINE TRANS UDPS se ache G ace amp eae Rw we Be Se eS 2 118 Rele
275. ability and convergence of a solution To allow the solver to do this you need to specify the dependent relationship between the source and solution variables in your UDF in the form of derivatives The source term Sy depends only on the solution variable Vz Its derivative with respect to Uy is OS Oe 6 8 2 2 The following UDF specifies a source term and its derivative The function named cell_x_source is defined on a cell using DEFINE_SOURCE The constant C in Equa tion 8 2 1 is called CON in the function and it is given a numerical value of 20 kg m s which will result in the desired units of N m for the source The temperature at the cell is returned by C_T cell thread The function checks to see if the temperature is below or equal to 288 K If it is the source is computed according to Equation 8 2 1 C_U returns the value of the x velocity of the cell If it is not the source is set to 0 At Release 12 0 ANSYS Inc January 26 2009 8 25 Examples the end of the function the appropriate value for the source is returned to the ANSYS FLUENT solver Table 8 2 1 Properties of the Liquid Metal Property Value Density 8000 kg m Viscosity 5 5 x107 kg m s Specific Heat 680 J kg K Thermal Conductivity 30 W m K PLT T TTT eT CeTCCTTCCrCLerCrrrCrrrcrrrrrrrrrrrrrrererrrrrrrrererre eet 7 UDF that adds momentum source term and derivative to duct flow TEtP Ct CTC CCCCerrrrrrcrrreretttrcr
276. able on the host Thread thread face_t face real area ND_ND endif RP_HOST Get the value of the thread ID from a user defined Scheme variable if RP_NODE SERIAL or HOST surface_thread_id RP_Get_Integer pres_av thread id Message nCalculating on Thread d n surface_thread_id endif RP_NODE To set up this user Scheme variable in cortex type rp var define pres_av thread id 2 integer f After set up you can change it to another thread s ID using rpsetvar pres_av thread id 7 Send the ID value to all the nodes host_to_node_int_1 surface_thread_id Does nothing in serial Release 12 0 ANSYS Inc January 26 2009 7 37 Parallel Considerations if RP_NODE Message nNode d is calculating on thread d n myid surface_thread_id endif RP_NODE if RP_HOST SERIAL or NODE thread is only used on compute processes thread Lookup_Thread domain surface_thread_id begin_f_loop face thread If this is the node to which face officially belongs get the area vector and pressure and increment the total area and total force values for this node if PRINCIPAL_FACE_P face thread Always TRUE in serial version F_AREA area face thread total_area NV_MAG area total_force NV_MAG area F_P face thread end_f_loop face thread Message Total Area Befor
277. acent Zone fluid move Cell Height mm g nonconst_height slibudF he bed Adjacent Zone Fluid move Cell Height mm g constant v Figure 6 5 3 The Dynamic Mesh Zones Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 5 Hooking Dynamic Mesh UDFs Select Stationary Rigid Body or User Defined from the Type list in the Dynamic Mesh Zones dialog box Click the Meshing Options tab and select the UDF library e g nonconst_height libudf from the Cell Height drop down list Finally click Create and close the Dynamic Mesh Zones dialog box See Section 2 6 2 DEFINE_DYNAMIC_ZONE_PROPERTY for further details about DEFINE_DYNAMIC_ZONE_PROPERTY functions 6 5 3 Hooking DEFINE_GEOM UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE_GEOM UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones dialog box To hook the UDF to ANSYS FLUENT you will first need to enable the Dynamic Mesh option in the Dynamic Mesh task page Dna Dynamic Mesh Next open the Dynamic Mesh Zones dialog box Figure 6 5 4 Dynamic Mesh Create Edit Select Deforming under Type in the Dynamic Mesh Zones dialog box Figure 6 5 4 and click the Geometry Definition tab Select user defined in the Definition drop down list and select the function name e g parabola libudf from the Geometry UDF drop down list
278. acros e Section 1 5 Interpreting and Compiling UDF s e Section 1 6 Hooking UDFs to Your ANSYS FLUENT Model e Section 1 7 Mesh Terminology e Section 1 8 Data Types in ANSYS FLUENT e Section 1 9 UDF Calling Sequence in the Solution Process e Section 1 10 Special Considerations for Multiphase UDFs 1 1 What is a User Defined Function UDF A user defined function or UDF is a function that you program that can be dynamically loaded with the ANSYS FLUENT solver to enhance the standard features of the code For example you can use a UDF to define your own boundary conditions material properties and source terms for your flow regime as well as specify customized model parameters e g DPM multiphase models initialize a solution or enhance postprocessing See Section 1 2 Why Use UDFs for more examples UDFs are written in the C programming language using any text editor and the source code file is saved with a c extension e g myudf c One source file can contain a single UDF or multiple UDFs and you can define multiple source files See Appendix A for some basic information on C programming Release 12 0 ANSYS Inc January 26 2009 1 1 Overview UDFs are defined using DEFINE macros provided by ANSYS FLUENT see Chapter 2 DEFINE Macros They are coded using additional macros and functions also supplied by AN SYS FLUENT that access ANSYS FLUENT solver data and perform other tasks See Chapter 3 Additional Macr
279. aded library the other functions in the library can safely use C_UDMI c t offset up to C_UDMI c t offset num 1 to store values in user scalars without interference Unreserving UDS Variables ANSYS FLUENT does not currently provide the capability to unreserve UDS variables using a macro Unreserve macros will be available in future versions of ANSYS FLUENT N_UDS You can use N_UDS to access the number of user defined scalar UDS transport equations that have been specified in ANSYS FLUENT The macro takes no arguments and returns the integer number of equations It is defined in models h 3 46 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros 3 2 9 User Defined Memory UDM Macros This section contains macros that access user defined memory UDM variables in ANSYS FLUENT Before you can store variables in memory using the macros provided below you will first need to allocate the appropriate number of memory location s in the User Defined Memory dialog box in ANSYS FLUENT See Section 6 1 8 User Defined Memory Storage for more details Define gt User Defined Memory Note that if you try to use F_UDMI or C_UDMI before you have allocated memory then an error will result A variable will be created for every user defined memory location that you allocate in the graphical user interface For example if you specify 2 as the Number of User Defined Memory then two variables
280. ager dialog box Figure 5 5 2 Define gt User Defined Functions gt Manage UDF Library Manager UDF Libraries libud o Library Name Figure 5 5 2 The UDF Library Manager Dialog Box In the UDF Library Manager dialog box highlight the shared library name e g libudf that is listed under UDF Libraries or type the Library Name and click Unload Fig ure 5 5 2 After it is unloaded the library e g libudf will be removed from the UDF Libraries list in the dialog box Repeat this step to unload additional libraries 5 6 Common Errors When Building and Loading a UDF Library A common compiler error occurs when you forget to put an include udf h statement at the beginning of your source file You ll get a long list of compiler error messages that include illegal declarations of variables Similarly if your function requires an auxiliary header file e g sg_ pdf h and you forgot to include it you ll get a similar compiler error message Another common error occurs when the argument list for a DEFINE statement is placed on multiple lines All DEFINE macro arguments must be listed on the same line in a C file The compiler will typically not report any error message but it will report a single warning message in the log file to indicate that this occurred warning no newline at end of file 5 26 Release 12 0 ANSYS Inc January 26 2009 5 6 Common
281. al There are seven arguments to DEFINE_MASS_TRANSFER name c mixture_thread from_phase_index from_species_index to_phase_index to_species_index You sup ply name the name of the UDF The variables c mixture_thread from_phase_index from_species_index to_phase_index and to_species_index are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value of the mass transfer to the solver in the units of kg m s Release 12 0 ANSYS Inc January 26 2009 2 1 49 DEFINE Macros The arguments from_species_index and to_species_index are relevant for multiphase species transport problems only and only if the respective phase has a mixture material associated with it Example The following UDF named lig_gas_source specifies a simple mass transfer coefficient based on saturation temperature Note that in the example that follows the DEFINE_MASS_TRANSFER state ment is broken up into two lines for the sake of readability In your source file you must make sure that the DEFINE statement is on one line only UDF to define a simple mass transfer based on Saturation Temperature The from phase is the gas and the to phase is the liquid phase include udf h DEFINE_MASS_TRANSFER liq_gas_source cell thread from_index from_species_index to_index to_species_index real m_lg real T_SAT 373 15 Thread gas THREAD_SUB_THREAD thread from_index Thread ligq THREAD_SUB_THRE
282. al conductivity See below for list of variables real T Temperature at which the property is to be evaluated used only if a polynomial method is specified Function returns real Release 12 0 ANSYS Inc January 26 2009 2 89 DEFINE Macros MATERIAL_PROPERTY is defined in materials h and returns a real pointer to the Property array prop for the given material pointer m MATERIAL PROPERTY m Argument Type Description Material m Material pointer Function returns real THREAD_MATERIAL is defined in threads h and returns real pointer m to the Material that is associated with the given cell thread t Note that in previous versions of FLUENT THREAD MATERIAL took two arguments t i but now only takes one t THREAD_MATERIAL t Argument Type Description Thread t Pointer to cell thread Function returns real mixture_species_loop is defined in materials h and loops over all of the species for the given mixture material mixture species loop m sp i Argument Type Description Material m Material pointer Material sp Species pointer int i Species index Function returns real 2 90 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 1 Temperature dependent Viscosity Property The following UDF named cell_viscosity generates a variable viscosity profile to simulate solidification The function is called for every cell in the zone The viscosity in the war
283. ame can include letters numbers and the underscore _ character Note that the C preprocessor is case sensitive recognizes uppercase and lowercase letters as being different Below are some examples of variable declarations int n declaring variable n as an integer int i1 i2 declaring variables il and i2 as integers float tmax 0 tmax is a floating point real number that is initialized to 0 real average_temp 0 0 average_temp is a real number initialized to 0 0 A 5 2 External Variables If you have a global variable that is declared in one source code file but a function in another source file needs to use it then it must be defined in the other source file as an external variable To do this simply precede the variable declaration by the word extern as in extern real volume If there are several files referring to that variable then it is convenient to include the extern definition in a header h file and include the header file in all of the c files A 4 Release 12 0 ANSYS Inc January 26 2009 A 5 Variables that want to use the external variable Only one c file should have the declaration of the variable without the extern keyword Below is an example that demonstrates the use of a header file i extern can be used only in compiled UDFs Example Suppose that there is a global variable named volume that is declared in a C source file named file1 c include udf h real vol
284. an integer that is a numerical label for the variable being set within each loop The function begins by declaring variable f as a face_t data type A one dimensional array x and variable y are declared as real data types A looping macro is then used to loop over each face in the zone to create a profile or an array of data Within each loop F_CENTROID outputs the value of the face centroid array x for the face with index f that is on the thread pointed to by thread The y coordinate stored in x 1 is assigned to variable y and is then used to calculate the x velocity This value is then assigned to F_PROFILE which uses the integer position passed to it by the solver based on your selection of the UDF as the boundary condition for x velocity in the Velocity Inlet dialog box to set the x velocity face value in memory DORR ooo o kkk k A A 2k kk kkk kkk A A A kkk kkk kkk kkk vprofile c UDF for specifying steady state velocity profile boundary condition EEEE ooo ooo o kkk k kkk 2 2k 2k 2k 2k 2k include udf h DEFINE_PROFILE inlet_x_velocity thread position real x ND_ND this will hold the position vector real y h face_t f h 0 016 inlet height in m begin_f_loop f thread F_CENTROID x f thread y 2 x 1 0 5 h h non dimensional y coordinate F_PROFILE f thread position 0 1 1 0 y y end_f_loop f thread 8 16 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Exa
285. and Eyzat 3 On 3800 T 0 01768 p exp 2 3 5 Here ON is the octane number of the fuel p is the absolute pressure in atmospheres and T is the temperature in Kelvin Release 12 0 ANSYS Inc January 26 2009 2 47 DEFINE Macros In the following UDF example the Douaud and Eyzat correlation is used to calculate an induction time Please see Chapter 3 Additional Macros for Writing UDFs for details on the NNULLP C_STORAGE_R C_PREMIXC_T C_P C_R CURRENT_TIMESTEP and C_IGNITE macros used below This UDF produces an ignition model source in ANSYS FLUENT 12 0 that uses the default parameters for the correlation of Douaud and Eyzat for knock include udf h real A 0 01768 Preexponential real Ea 3800 Activation temperature real O_N 90 0 Octane number real 0_E 3 402 Octane number exponent real P_E 1 7 Pressure exponent static real A1 0 0 Cached value of A 0ON OE static real dt 0 0 Cached time step static real p_op 0 0 Cached value of operating pressure static cxboolean lit FALSE Cached burning flag DEFINE_IGNITE_SOURCE ign_udf_src c t source real rho C_R c t real time 0 0 real prog NNULLP THREAD_STORAGE t SV_PREMIXC_M1 C_STORAGE_R c t SV_PREMIXC_M1 C_STORAGE_R c t SV_PREMIXC real fuel 1 0 prog real T C_PREMI
286. and UDS Variables for an example of F_UDSI usage Table 3 2 35 Accessing User Defined Scalar Face Variables mem h Macro Argument Types Returns F UDSI f t i face t f Thread t int i UDS face variables Note i is index of scalar i Note that F_UDSI is available for wall and flow boundary faces only If a UDS attempts to access any other face zone then an error will result C_UDSI You can use C_UDSI when you want to access cell variables that are computed for user defined scalar transport equations Macros for accessing UDS cell variables are listed in Table 3 2 36 Some examples of usage for these macros include defining non constant source terms for UDS transport equations and initializing equations See Sec tion 3 2 9 Example UDF that Utilizes UDM and UDS Variables for an example of C_UDSI usage Table 3 2 36 C_UDSI for Accessing UDS Transport Cell Variables mem h Macro Argument Types Returns C UDSI c t i cell t c Thread t int i UDS cell variables C_UDSI G c t i cell t c Thread t int i UDS gradient C_UDSI_M1 c t i cell_t c Thread t int i UDS previous time step C_UDSI_M2 c t i cell_t c Thread t int i UDS second previous time step C_UDSI_DIFF c t i cell_t c Thread t int i UDS diffusivity Note i is index of scalar Release 12 0 ANSYS Inc January 26 2009 3 45 Additional Macros for Writing UDFs Reserving UDS Variables Reserve User Scalar
287. and a frequency of 10 rad s The source file listing for the UDF that describes the transient outlet profile is shown below The function named unsteady_pressure is defined using the DEFINE_PROFILE macro The utility CURRENT_TIME is used to look up the real flow time which is assigned to the variable t See Section 3 5 Time Dependent Macros for details on CURRENT_TIME PROC kkk kkk kkk kk kkk kkk kkk kkk kkk kk k kk unsteady c UDF for specifying a transient pressure profile boundary condition EEEE ooo ooo o kkk k kkk 2 2 2k kkk include udf h DEFINE_PROFILE unsteady_pressure thread position face_t f real t CURRENT_TIME begin_f_loop f thread F_PROFILE f thread position 101325 0 5 0 sin 10 t end_f_loop f thread Release 12 0 ANSYS Inc January 26 2009 8 19 Examples Before you can interpret or compile the UDF you must specify a transient flow calculation in the General task page Then follow the procedure for interpreting source files using the Interpreted UDFs dialog box Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box or compiling source files using the Compiled UDFs dialog box Section 5 2 Compiling a UDF Using the GUI The sinusoidal pressure boundary condition defined by the UDF can now be hooked to the outlet zone In the Pressure Outlet dialog box Figure 8 2 7 simply select the name of the UDF given in this example with the word udf p
288. and su You supply name the name of the UDF c t and i are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the values of the unsteady terms referenced by the real pointers apu and su to the central coefficient and source term respectively The ANSYS FLUENT solver expects that the transient term will be decomposed into a source term su and a central coefficient term apu These terms are included in the equation set in a similar manner to the way the explicit and implicit components of a source term might be handled Hence the unsteady term is moved to the right hand side and discretized as follows unsteady term Z 69 dV p9 po AV pAV n 4 PAV p1 Tna 2 7 3 _e _e _ apu su Equation 2 7 3 shows how su and apu are defined Note that if more than one scalar is being solved a conditional if statement can be used in your UDF to define a different unsteady term for each i i 0 is associated with scalar 0 the first scalar equation being solved Example The following UDF named my_uds_unsteady modifies user defined scalar time deriva tives using DEFINE UDS UNSTEADY The source code can be interpreted or compiled in ANSYS FLUENT k k k k 2k 2k 2k 2k 2k ak ak k k k k k 2k 2k 2K 2K A 2K 2K 2K 2K FK 2K 2K 2K 2K 2K K K K 2K FK FK 2K 2K A A 2K K AK 2K FK aK a 2k 2k FK 2k 2k K 24 K K 2k 2k K K KK aK UDF for specifying user defined scalar time derivativ
289. anuary 26 2009 8 2 Detailed UDF Examples 1 41e 01 1 27e 01 1 12e 01 9 84e 02 8 44e 02 7 03e 02 5 62e 02 4 22e 02 2 81e 02 1 41e 02 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 2 Velocity Magnitude Contours for a Constant Inlet x Velocity 1 43e 01 1 31e 01 1 196 01 tieto fae a hl Sa eS 94280 Yh at ig ote a ak eh ah eh ate ee B 20e 02 6 9e 02 J ee ee eK 5 75e 02 4 52e 02 3 30e 02 2 076 02 Velocity Vectors Colored By Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 3 Velocity Vectors for a Constant Inlet x Velocity Release 12 0 ANSYS Inc January 26 2009 8 15 Examples Now suppose that you want to impose a non uniform x velocity to the duct inlet which has a parabolic shape The velocity is 0 m s at the walls of the inlet and 0 1 m s at the center A UDF is used to introduce this parabolic profile at the inlet The C source code vprofile c is shown below The function makes use of ANSYS FLUENT supplied solver functions that are described in Section 3 2 4 Face Macros The UDF named inlet_x_velocity is defined using DEFINE_PROFILE and has two ar guments thread and position Thread is a pointer to the face s thread and position is
290. ap rhoV c sqrt 2 0 3 0 rhoL c ABS p_vapor ABS_P p c The condensation rate is If ABS_P gt p_vapor then c_con rhoL c sqrt 2 0 3 0 rhoL c ABS p_vapor ABS_P pI c where c_evap and c_con are model coefficients 2 1 38 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros DOR k kk k kkk kkk kkk kkk kk kk kk kkk kk k I I I I I kk kk k kkk A A k kkk k kkk k k Kk k UDF that is an example of a cavitation model different from default Can be interpreted or compiled EEEE oo o I A I I OK KKK o kkk k kkk kk kkk 2k 2k include udf h define c_evap 1 0 define c_con 0 1 DEFINE_CAVITATION_RATE c_rate c t p rhoV rhoL mafV p_v cigma f_gas m_dot real p_vapor p_v real dp dp0 source p_vapor MIN 0 195 C_R c t C_K c t 5 0 p_vapor dp p_vapor ABS_P plic op_pres dpO MAX 0 1 ABS dp source sqrt 2 0 3 0 rhoL c dp0 if dp gt 0 0 m_dot c_evap rhoV c source else m_dot c_con rhoL c source Hooking a Cavitation Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE CAVITATION RATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g c_rate will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs for detai
291. application of the user defined function The viscosity varies rapidly over a narrow spatial band from a constant value of 0 0055 to 1 0 kg m s The velocity field Figure 8 2 21 demonstrates that the liquid slows down in response to the increased viscosity as expected In this model there is a large mushy region in which the motion of the fluid gradually decreases This is in contrast to the first model in which a momentum source was applied and a more abrupt change in the fluid motion was observed Release 12 0 ANSYS Inc January 26 2009 8 33 Examples 1 00e 00 9 50e 01 9 01e 01 8 51e 01 8 01e 01 7 51e 01 7 02e 01 6 52e 01 6 02e 01 5 52e 01 5 03e 01 4 53e 01 4 03e 01 3 54e 01 3 04e 01 2 54e 01 2 04e 01 1 55e 01 1 05e 01 5 52e 02 5 50e 03 Contours of Molecular Viscosity kg m s FLUENT 12 0 2d pbns LUENT 12 0 2d pbns lam Figure 8 2 20 Laminar Viscosity Generated by a User Defined Function 1 76e 03 1 67e 03 1 58e 03 1 49e 03 1416 03 1 32e 03 1 23e 03 1 14e 03 1 05e 03 9 676 04 8 79e 04 7 91e 04 7 03e 04 6 156 04 5 27e 04 4 39e 04 3 52e 04 2 646 04 1 766 04 8 79e 05 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 21 Contours of Velocity Magnitude Resulting from a User Defined Viscosity 8 34 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples aie ANSYS 7 606 00 7 20e 0
292. arameter Pollut_Par SOx_Parameter S0x Pollut_Par gt nfstreams Number of fuel streams Pollut gt r_fuel_gls i Rate of volatile release for stream i per unit volume in kg m3 sec SOx gt Ys_fuelvolat i Mass fraction of S in volatile stream i SOx gt fuels_so2_frac i Partition fraction of S02 in stream i real kf kr rf 0 rr 0 real o_eq real r_volatile Ys_volatile fuels_so2_frac Release 12 0 ANSYS Inc January 26 2009 2 1 09 DEFINE Macros Rate_Const K_F 1 2e6 0 0 39765 575 Rate_Const K_R 1 0e4 1 0 10464 625 Rate_Const K_O 36 64 0 5 27123 0 S03 0 lt gt S02 02 kf ARRH Pollut KF kr ARRH Pollut K_R o_eq ARRH Pollut K_0 sqrt MOLECON Pollut 02 if POLLUT_EQN Pollut_Par EQ_S02 int ifstream Ys_volatile 1 e 04 fuels_so2_frac 1 for ifstream 0 ifstream lt Pollut_Par gt nfstreams ifstream rf Pollut gt r_fuel_gls ifstream SOx gt Ys_fuelvolat ifstream SOx gt fuels_so2_frac ifstream 1000 Pollut_Par gt sp S mw rf kf o_eq MOLECON Pollut IDX S03 rr kr MOLECON Pollut 02 MOLECON Pollut IDX S02 else if POLLUT_EQN Pollut_Par EQ_S03 rf kr MOLECON Pollut 02 MOLECON Pollut IDX S02 rr kf o_eq MOLECON Pollut IDX S03 POLLUT_FRATE Pollut rf POLLUT_RRATE Pollut rr Example 2 The following compiled UDF named sox_func_name specifies a custom maximum limi
293. are zero but it is good programming practice to exclude the host See Section 7 5 Macros for Parallel UDFs for details on compiler directives Next a user defined Scheme variable named pres_av thread id is obtained by the host and serial process using the RP_Get_Integer utility see Section 3 6 Scheme Macros and is assigned to the variable surface_thread_id Note that this user defined Scheme variable was previously set up in Cortex and assigned a value of 2 by typing the text commands shown in the comments After a Scheme based variable is set up for the thread ID it can be easily changed to another thread ID from the text interface without the burden of modifying the source code and recompiling the UDF Since the host com municates with Cortex and the nodes are not aware of Scheme variables it is essential to direct the compiler to exclude the nodes from compiling them using if RP_NODE Failure to do this will result in a compile error The surface_thread_id is then passed from the host to compute node 0 using the host_to_node macro Compute node 0 in turn automatically distributes the variable to the other compute nodes The serial and node processes are directed to loop over all faces in the thread associated with the surface_thread_id using if RP_HOST and compute the total area and total force Since the host does not contain any thread data it will ignore these statements if you do not direct the compiler but it is good pro
294. ariable array similar to the description of PRF_GRSUM x N iwork on the previous page The same naming convention used for PRF_GHIGH macros applies to PRF_GLOW 7 20 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Global Maximums Macro Action PRF_GIHIGH1 x Returns maximum of integer x over all compute nodes PRF_GIHIGH x N iwork Sets x to contain maximums over all compute nodes PRF_GRHIGH1 x Returns maximums of x over all compute nodes float if single precision double if double precision PRF_GRHIGH x N iwork Sets x to contain maximums over all compute nodes float array if single precision double array if double precision Global Minimums Macro Action PRF_GILOW1 x Returns minimum of integer x over all compute nodes PRF_GILOW x N iwork Sets x to contain minimums over all compute nodes PRF_GRLOW1 x Returns minimum of x over all compute nodes float if single precision double if double precision PRF_GRLOW x N iwork Sets x to contain minimums over all compute nodes float array if single precision double array if double precision Global Logicals Macros that can be used to compute global logical ANDs and logical ORs are identified by the suffixes AND and OR respectively PRF_GLOR1 x computes the global logical OR of variable x across all compute nodes PRF_GLOR x N iwork computes the global logical OR of variable array x The elements of x are set to TRUE if any of the cor
295. ary 26 2009 3 2 Data Access Macros Number of Faces C_NFACES and Nodes C_NNODES in a Cell The macro C_NFACES shown in Table 3 2 5 returns the integer number of faces for a given cell C_NNODES also shown in Table 3 2 2 returns the integer number of nodes for a given cell Table 3 2 5 Macros for Number of Node and Faces Defined in mem h Macro Argument Types Returns C_NNODES c t C_NFACES ct cell_t c Thread t cell_t c Thread t int number of nodes in a cell int number of faces in a cell Cell Face Index C_FACE C_FACE expands to return the global face index face_t f for the given cell_t c Thread t and local face index number i Specific faces can be accessed via the integer index i and all faces can be looped over with c_face_loop The macro is defined in mem h Table 3 2 6 Macro for Cell Face Index Defined in mem h Macro Argument Types Returns C FACE c t i cell t c Thread t int i global face index facet f Cell Face Index C_FACE_THREAD C_FACE_THREAD expands to return the Thread t of the face_t f that is returned by C_FACE see above Specific faces can be accessed via the integer index i and all faces can be looped over with c_face_loop The macro is defined in mem h Table 3 2 7 Macro for Cell Face Index Defined in mem h Macro Argument Types Returns C_FACE_THREAD cell t c Thread t int i Thread t
296. ary 26 2009 3 73 Additional Macros for Writing UDFs ND_CROSS_X x 0 x 1 x 2 uf0 y 1 y 2 NV_CROSS_Y x y ND_CROSS_X x 0 x 1 x 2 ul0 y 1 y 2 NV_CROSS_Z x y ND_CROSS_X x 0 x 1 x 2 ul0 y 1 y 2 NV_CROSS a x y a 0 NV_CROSS_X x y a 1 NV_CROSS_Y x y al2 NV_CROSS_Z x y See Section 2 6 4 DEFINE GRID MOTION for an example UDF that utilizes NV_CROSS 3 5 Time Dependent Macros You can access time dependent variables in your UDF in two different ways direct access using a solver macro or indirect access using an RP variable macro Table 3 5 1 contains a list of solver macros that you can use to access time dependent variables in ANSYS FLUENT An example of a UDF that uses a solver macro to access a time dependent variable is provided below See Section 2 2 2 DEFINE_DELTAT for another example that utilizes a time dependent macro Table 3 5 1 Solver Macros for Time Dependent Variables Macro Name Returns CURRENT_TIME real current flow time in seconds CURRENT_TIMESTEP real current physical time step size in seconds PREVIOUS_TIME real previous flow time in seconds PREVIOUS _2 TIME real flow time two steps back in time in seconds PREVIOUS_TIMESTEP real previous physical time step size in seconds N_TIME integer number of time steps N_ITER integer number of iterations i You must include the unsteady h header file in your UDF source code when using the PREVIO
297. ary Face Geometry BOUNDARY FACE GEOMETRY BOUNDARY FACE GEOMETRY f t A ds es A by_es dr0 expands to a function that out puts the following variables to the solver for a given face f on face thread t It is defined in the sg h header file which is not included in udf h You will need to include this file in your UDF using the include directive Release 12 0 ANSYS Inc January 26 2009 3 27 Additional Macros for Writing UDFs BOUNDARY_FACE_GEOMETRY can be called to retrieve some of the terms needed to evaluate Equations 3 2 1 and 3 2 3 real A ND_ND area normal vector real ds distance between the cell centroid and the face centroid real es ND_ND unit normal vector in the direction from centroid of cell c0 to the face centroid real A byes value ae real drO ND_ND vector that connects the centroid of cell cO to the face centroid Boundary Face Thread BOUNDARY_FACE_THREAD BOUNDARY FACE THREAD P t expands to a function that returns TRUE if Thread t is a boundary face thread The macro is defined in threads h which is included in udf h See Section 2 7 3 DEFINE_UDS_FLUX for an example UDF that utilizes BOUNDARY_FACE_THREAD_P Boundary Secondary Gradient Source BOUNDARY SECONDARY GRADIENT SOURCE BOUNDARY SECONDARY GRADIENT SOURCE source n dphi dx A by_es k expands to a func tion that outputs the following variables to the solver for a given face and face thread It is defined in the sg h header file which i
298. ary phase s mixture mixture mixture mixture mixture mixture mixture mixture mixture Material Properties granular diameter granular solids pressure granular radial distribution granular elasticity modulus granular viscosity granular temperature DEFINE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE_PROPERTY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s Release 12 0 ANSYS Inc January 26 2009 Quick Reference Guide for Multiphase DEFINE Macros Table C 3 3 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE_MASS_TRANSFER DEF INE_HET_RXN_RATE phase interaction phase interaction phase interaction phase interaction phase interaction C 4 Eulerian Model Mixture Turbulence Flow Tables C 4 1 C 4 3 list the variables that can be customized using UDFs for the mixed turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Table C 4 1 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flo
299. as 2 4 1 Release 12 0 ANSYS Inc January 26 2009 2 1 45 DEFINE Macros Here gas is a primary phase mixture of two species HzO gqs and air Droplets constitute the secondary phase and represent a mixture of one species H2O iq Single species mixtures are allowed in multiphase models The formulation for the reaction rate follows the model for particle evaporation that is defined in Section 15 4 2 Droplet Vaporization Law 2 in the separate Theory Guide include udf h Constants used in psat_h2o to calculate saturation pressure define PSAT_A 0 01 define PSAT_TP 338 15 define C_LOOP 8 define H20_PC 22 089E6 define H20_TC 647 286 xuser inputs define MAX_SPE_EQNS_PRIM 2 total number of species in primary phase define index_evap_primary 0 x evaporating species index in primary phase define prim_index 0 xindex of primary phase define P_OPER 101325 xoperating pressure equal to GUI valuex end of user inputs DOR k kkk k kkk k kkk kkk k kkk kkk k kkk k kkk A k kkk k kkk kkk k k UDF for specifying an interfacial area density pakao oE E k kk kkk double psat_h2o double tsat 2 146 Computes saturation pressure of water vapor as function of temperature Equation is taken from THERMODYNAMIC PROPERTIES IN SI by Reynolds 1979 Returns pressure in PASCALS given temperature in KELVIN int i double vari sumi ans
300. as been provided that will display the available gradients in the console See the previous section for details Previous Time Step Macros The M1 suffix can be applied to some of the cell variable macros in Table 3 2 8 to allow access to the value of the variable at the previous time step i e t At These data may be useful in unsteady simulations For example C_T_Mi c t returns the value of the cell temperature at the previous time step Previous time step macros are shown in Table 3 2 11 i Note that data from C_T_M1 is available only if user defined scalars are defined It can also be used with adaptive time stepping Table 3 2 11 Macros for Cell Time Level 1 Defined in mem h Macro Argument Types Returns CRM1 c t cell_t c Thread t density previous time step CPM1 c t cell t c Thread t pressure previous time step C_UM1 c t cell_t c Thread t velocity previous time step CVMi c t cell_t c Thread t velocity previous time step CWMi c t cell t c Thread t velocity previous time step C_T_M1i c t cell t c Thread t temperature previous time step C_YIM1 c t i cell_t c Thread t int i species mass fraction note int i is species index previous time step See Section 2 7 4 DEFINE_UDS_UNSTEADY for an example UDF that utilizes C_R_M1 3 16 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros The M2 suffix can be applied to some of the cell variable macros in Tabl
301. as test conditions in your UDF The following predicates return TRUE if the condition in the parenthesis is met predicate definitions from para h header file define MULTIPLE_COMPUTE_NODE_P compute_node_count gt 1 define ONE_COMPUTE_NODE_P compute_node_count 1 define ZERO_COMPUTE_NODE_P compute_node_count 0 There are a number of predicates that allow you to test the identity of the node pro cess in your UDF using the compute node ID A compute node s ID is stored as the global integer variable myid see Section 7 7 Process Identification Each of the macros listed below tests certain conditions of myid for a process For example the predicate I_AM NODE_ZERO_P compares the value of myid with the compute node 0 ID and returns TRUE when they are the same I_AM_NODE_SAME_P n on the other hand compares the compute node ID that is passed in n with myid When the two IDs are the same the function returns TRUE Node ID predicates are often used in conditional if statements in UDFs predicate definitions from para h header file define I_AM_NODE_HOST_P myid node_host define I_AM_NODE_ZERO_P myid node_zero define I_AM_NODE_ONE_P myid node_one define I_AM_NODE_LAST_P myid node_last define I_AM_NODE_SAME_P n myid n define I_AM_NODE_LESS_P n myid lt n define I_AM_NODE_MORE_P n myid gt n HH H H H OF Release 12 0 ANSYS Inc January 26 2009 7 17 Parallel Conside
302. ase 12 0 ANSYS Inc January 26 2009 CONTENTS 2 39 24 DEFINE TURB_PREMIX SOURCE gt se s cu miat du 4 Gav oe ws 2 122 2 39 29 DEFINE TURE SCHMIDT UDP ss naa heh a Bee Rw Ae 2 124 2 0 20 DEFINE TURBULENT VISGUSLTY i s d mo eg 8444444444 2 125 23921 DEFINE VRRATE c e on eed eR BO Pa HRY Se e Pet eee 2 129 Zoe DEFINE WALL FUNCTIONS p 2 g siroa e i a bh a ee SG 2 133 2 4 Multiphase DEFINE Macros 0 00002 eee eee 2 135 24 1 DEFINE CAVITATION RATE soei hae Sa we i a E a E w 2 137 242 DEFINE_EXCHANGE PROPERIY 2 24 cs roere a eG eG eas 2 139 2A DEFINE HET RXN RATE 233 545 44682 44 2 644629 6 amp 4 2 144 JAA DEFINE MASS TRANGFER lt s i022 ea bee eed eee eee he 2 149 24 5 DEFINE _VECTOR EXCHANGE PROPERTY gt o ses ee ee dave eens 2 151 2 5 Discrete Phase Model DPM DEFINE Macros 2 154 2 5 1 DEFINE DPM BO 24454544644 6 64 bee Rb eRe S 2 156 2 0 2 DEFINE DPM BODY FORCGE o a ee as es eg ey cg a ES RE ia 2 163 Zou DEPINE DPM DRAG cco sacp iaia aa 4 ae w A eee ee G 2 165 So DEFINE DPM EROSION o soear 234 kan be wee Soe ded 2 167 2 000 DEFINE DPM MEAT MAGS ooo se aw ES eke Ew Be ete we a 2 173 220 0 DEFINE DPM INJECTION INIT so Woe eh Row Ree Bede a 2 177 2 0 DEFINE DPM LAW pgp sceo pecen Bd Deck Ga Sed p pik 2 181 2 0 9 DEFINE DPM_OQUTPUT lt a sos 4 aomu a coe d ea ROS a a a 2 183 2209 DEFINE DPM PROPEREY ie sioti Soap u an ea E a a a i A S 2 186 20 10 DEFINE DPM SCALAR UPDATE a sos cov
303. ase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Release 12 0 ANSYS Inc January 26 2009 C 6 Eulerian Model Per Phase Turbulence Flow Table C 5 3 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEF INE_EXCHANGE DEFINE EXCHANGE DEFINE PROPERTY DEFINE_MASS_TRANSFER DEF INE_HET_RXN_RATE phase interaction phase interaction phase interaction phase interaction phase interaction C 6 Eulerian Model Per Phase Turbulence Flow Tables C 6 1 C 6 3 list the variables that can be customized using UDFs for the per phase turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Table C 6 1 DEFINE Macro Usage for the Eulerian Model Per Phase Tur bulence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magnitude temperature pressure user defined scalar boundary value DEFINE_PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE s
304. at you have defined using DEFINE_EXECUTE_AT_EXIT is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable via the User Defined Function Hooks dialog box in ANSYS FLU ENT Note that you can hook multiple at exit UDFs to your model For details see Section 6 1 4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs 2 2 5 DEFINE_EXECUTE_FROM_GUI Description DEFINE EXECUTE FROM GUI is a general purpose macro that you can use to define a UDF which is to be executed from a user defined graphical user interface GUI For example a C function that is defined using DEFINE_EXECUTE_FROM_GUI can be executed whenever a button is clicked in a user defined GUI Custom GUI components dialog boxes buttons etc are defined in ANSYS FLUENT using the Scheme language Usage DEF INE_EXECUTE_FROM_GUI name 1ibname mode Argument Type Description symbol name UDF name char libname name of the UDF library that has been loaded in ANSYS FLUENT int mode an integer passed from the Scheme program that defines the user defined GUI Function returns void There are three arguments to DEFINE_EXECUTE_FROM_GUI name libname and mode You supply name the name of the UDF The variables libname and mode are passed by the ANSYS FLUENT solver to your UDF The integer variable mode is passed from the Scheme program which defines the user
305. ate RATE c t C_LIQF c t cell t c Thread t liquid fraction in a cell C_POLLUT c t i cell_t c Thread t int i ith pollutant species mass fraction see table below i C_LIQF is available only in fluid cells and only if solidification is turned ON 3 20 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Table 3 2 17 Table of Definitions for Argument i of the Pollutant Species Mass Fraction Function C_POLLUT Definitions Mass Fraction of NO Mass Fraction of HCN Mass Fraction of NH3 Mass Fraction of N20 Soot Mass Fraction Normalized Radical Nuclei oP WDNR OO Note Concentration in particles x10 kg For mass fraction concentrations in the table above see Equation 13 3 7 in the separate Theory Guide for the defining equation Reynolds Stress Model Macros The macros listed in Table 3 2 18 can be used to return real variables for the Reynolds stress turbulence model in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in the metric h header file Table 3 2 18 Macros for Reynolds Stress Model Variables Defined in sg_mem h Macro Argument Types Returns C_RUU c t cell_t c Thread t wu Reynolds stress C_RVV c t cell t c Thread t vv Reynolds stress C_RWW c t cell_t c Thread t ww Reynolds stress C_RUV c t cell_t c Thread t uv Reynolds stress C_RVW c t cell_t c Thread t
306. ay of species molecular weights real yi Pointer to array of mass fractions of gas species at the surface and the coverage of site species or site fractions real rr Pointer to reaction rate Function returns void There are seven arguments to DEFINE_SR_RATE name f t r my yi and rr You supply name the name of the UDF After your UDF is compiled and linked the name that you have chosen for your function will become visible and selectable in the graphical user interface in ANSYS FLUENT f t r my and yi are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the reaction rate to the value referenced by the real pointer rr as shown in the examples below Example 1 Surface Reaction Rate Using Species Mass Fractions The following compiled UDF named arrhenius defines a custom surface reaction rate using species mass fractions in ANSYS FLUENT DOR OO OR a aK ak a 2k 2k a kk Custom surface reaction rate UDF TEC teC errr Crrrrrrrrrrrrrrrrrrrrrrerrrrtrrerrrrrrrrrrerrrrrerrrere rss 29 include udf h ARRHENIUS CONSTANTS define PRE_EXP 1e 15 define ACTIVE 1e 08 define BETA 0 0 real arrhenius_rate real temp return Release 12 0 ANSYS Inc January 26 2009 2 1 15 DEFINE Macros PRE_EXP pow temp BETA exp ACTIVE UNIVERSAL_GAS_CONSTANT temp Species numbers Must match order in ANSYS FLUENT dialog box define HF O define WF6 1 de
307. bc_reflect name p the tracked particle t the touched face thread f the touched face f_normal normal vector of touched face dim dimension of the problem 2 in 2d and 2d axi swirl 3 in 3d return is the status of the particle see enumeration of Path_Status in dpm h define V_CROSS a b r DEFINE_ Cr 0 a 1 b 2 b 1 a 2 r 1 a 2 b 0 b 2 a 0 r 2 a 0 b 1 b 0 a 1 DPM_BC bc_wall_jet p thread f f_normal dim Routine implementing the Naber and Reitz Wall impingement model SAE 880107 real real real real real real real normal 3 tan_1 3 tan_2 3 rel_vel 3 face_vel 3 alpha beta phi cp sp rel_dot_n vmag vnew dum Release 12 0 ANSYS Inc January 26 2009 2 1 59 DEFINE Macros real weber_in weber_out int i idim din cxboolean moving SV_ALLOCATED_P thread SV_WALL_GRID_V amp amp SV_ALLOCATED_P thread SV_WALL_V if RP_2D if rp_axi_swirl A real R sqrt P_POS p 1 P_POS p 1 P_POS p 2 P_POS p 2 if R gt 1 e 20 idim 3 normal 0 f_normal 0 normal 1 f_normal 1 P_POS p 1 R normal 2 f_normal 1 P_POS p 2 R else for i 0 i lt idim i normal i f_normal il else endif for i 0 i lt idim i normal i f_normal i Set up velocity vectors and calculate th
308. be applied using a DEFINE_PROFILE UDF The following UDF named inlet_mf adjusts the mass flow rate from 1 00kg s to 1 35kg s when the physical time step is greater than 0 2 seconds After it has been interpreted or compiled you can activate this UDF in the Mass Flow Inlet boundary condition dialog box in ANSYS FLUENT by selecting the UDF from the Mass Flow Rate drop down list include udf h DEFINE_PROFILE inlet_mf th i face_t f begin_f_loop f th if CURRENT_TIME lt 0 01 F_PROFILE f th i 3 0 else if CURRENT_TIME lt 0 02 amp amp CURRENT_TIME gt 0 01 F_PROFILE f th i 4 0 else F_PROFILE f th i 5 0 end_f_loop f th Hooking a Boundary Profile UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PROFILE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g vis_res will become vis ible and selectable in the appropriate boundary condition or cell zone condition dialog box e g the Velocity Inlet dialog box in ANSYS FLUENT See Section 6 2 15 Hooking DEFINE_PROFILE UDFs for details 2 86 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 16 DEFINE PROPERTY UDFs Description You can use DEFINE PROPERTY to specify a custom material property in ANSYS FLUENT for single phase and multiphase flows When you are writing a
309. bles listed in Table 3 2 9 by using the integer index i for each macro listed in Table 3 2 9 For example C_T_G c t i will access a component of the temperature gradient vector i C_R_G can be used only in the density based solver and C_P_G can be used only in the pressure based solver i C_YILG can be used only in the density based solver To use this in the pressure based solver you will need to set the rpvar species save gradients to t As stated previously the availability of gradient variables is affected by your solver selec tion which models are turned on the setting for the spatial discretization and whether the temporary solver memory is retained To make it easy for you to verify what gradient variables are available for your particular case and data files the following UDF named showgrad c is provided Simply compile this UDF run your solution and then hook the UDF using the Execute on Demand dialog box as described in Section 6 1 6 Hook ing DEFINE_ON_DEMAND UDFs The available gradient variables will be displayed in the console N XAXA 3 10 Fa Note that the showgrad c UDF is only useful for single phase models F KF KF KF KF ON Demand User Defined Functions to check on the availability of Reconstruction Gradient and Gradients for a given Solver and Solver settings Availability of Gradients amp Reconstruction Gradient
310. bol name UDF name cell_t c Cell index Thread mixture_thread Pointer to cell thread of mixture domain int second_column phase index Index of second phase in phase interaction int first_column phase_index Index of first phase in phase interaction real vector_result Pointer to slip velocity vector Function returns void Release 12 0 ANSYS Inc January 26 2009 2 1 51 DEFINE Macros There are six arguments to DEFINE_VECTOR_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index and vector_result You supply name the name of the UDF c mixture_thread second_column phase index first_column phase_index and vector_result are vari ables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointer to the slip velocity vector vector_result to the components of the slip velocity vector e g vector_result 0 vector_result 1 for a 2D problem Example The following UDF named custom_slip specifies a custom slip velocity in a two phase mixture problem i Note that in the example that follows the DEFINE_VECTOR_EXCHANGE_PROPERTY statement is broken up into two lines for the sake of readability In your source file you must make sure that the DEFINE statement is on one line only peaa ooo oo kkk k kkk kkk kkk A A A 1 21 kkk kkk kkk kkk UDF for a defining a custom slip velocity in a 2 phase mixture problem BOA AA
311. bol name UDF name face_t f Face index Thread t Pointer to face thread on which the user defined scalar flux is to be applied int i Index that identifies the user defined scalar for which the flux term is to be set Function returns real There are four arguments to DEFINE UDS FLUX name f t and i You supply name the name of the UDF f t and i are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value of the mass flow rate through the given face to the solver 2 230 Release 12 0 ANSYS Inc January 26 2009 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros The advection term in the differential transport equation has the following most general form V Yo O71 where is the user defined scalar conservation quantity and Y is a vector field In the default advection term w is by default the product of the scalar density and the velocity vector Madadi pv 2 7 2 To define the advection term in Equation 2 7 1 using DEFINE_UDS_FLUX your UDF needs to return the scalar value Y A to ANSYS FLUENT where Y is the same as defined in Equation 2 7 1 and A is the face normal vector of the face Note that the advective flux field that is supplied by your UDF should be divergence free i e it satisfies the continuity equation In discrete terms this means that the sum of fluxes over all the faces of each cell should be zero If the advective f
312. box Teta Dees Edit Enable the Mixture model in the Multiphase Model dialog box and click OK Enter the solve set expert text command in the console and respond yes to use Singhal et al cavitation model Then open the Phase Interaction dialog box lt EMERSA gt Interaction Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Singhal Et Al Cavitation Model Cavitation Parameters Ray Yaporization Pressure pascal constant 3540 Surface Tension Coefficient nfm constant 0 0717 Non Condensable Gas Mass Fraction constant 1 5e 05 Figure 6 3 1 The Phase Interaction Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 55 Hooking UDFs to ANSYS FLUENT Enable Singhal Et Al Cavitation Model in the Mass tab of the Phase Interaction dialog box Figure 6 3 1 and click OK Next open the User Defined Function Hooks dialog box Figure 6 3 2 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Chemistry Step Cavitation Mass Rate aPeSar rT v DO Source DO Diffuse Reflectivity DO Specular Reflectivity DO Emissivity Weighting Factor nar
313. but the calculation requires more memory to run You can access a component of a gradient vector by specifying it as an argument in the gradient vector call 0 for the component 1 for y and 2 for z For example C_T_G c t 0 returns the x component of the cell temperature gradient vector returns the x component of the temperature gradient vector Table 3 2 9 Macros for Cell Gradients Defined in mem h Macro Argument Types Returns C_R_G c t cell t c Thread t density gradient vector C_P_G c t cell t c Thread t pressure gradient vector C_UG c t cell_t c Thread t velocity gradient vector CVG c t cell_t c Thread t velocity gradient vector C_W_G c t cell_t c Thread t velocity gradient vector C_T_G c t cell_t c Thread t temperature gradient vector C_H_G c t cell _t c Thread t enthalpy gradient vector C_NUT_G c t cell_t c Thread t turbulent viscosity for Spalart Allmaras gradient vector C_K_G c t cell_t c Thread t turbulent kinetic energy gradient vector CDG c t cell t c Thread t turbulent kinetic energy dissipation rate gradient vector C060 6 cell_t c Thread t specific dissipation rate gradient vector C_YI_G c t i cell_t c Thread t int i species mass fraction note int i is species index gradient vector Release 12 0 ANSYS Inc January 26 2009 3 9 Additional Macros for Writing UDFs i Note that you can access vector components of each of the varia
314. c see Section A 5 3 Static Variables Global variables are typically declared at the beginning of a file after preprocessor directives as in include udf h real volume real variable named volume is declared globally DEFINE_ADJUST compute_volume domain code that computes volume of some zone volume Local variables are variables that are used in a single function They are created when the function is called and are destroyed when the function returns unless they are declared as static see Section A 5 3 Static Variables Local variables are declared within the body of a function inside the curly braces In the example below mu_lam and temp are local variables The value of these variables is not preserved after the function returns Release 12 0 ANSYS Inc January 26 2009 A 3 C Programming Basics DEFINE_PROPERTY cell_viscosity cell thread real mu_lam local variable real temp C_T cell thread local variable if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam A 5 1 Declaring Variables A variable declaration begins with the data type e g int followed by the name of one or more variables of the same type that are separated by commas A variable declaration can also contain an initial value and always ends with a semicolon Variable names must begin with a letter in C A n
315. c t real mu_t C_MU_T c t alpha rng_alpha 1 mu mu_t mu pr_k mu_t mutmu_t alpha mu return pr_k DEFINE_PRANDTL_D user_pr_d c t real pr_d alpha real mu C_MU_L c t real mu_t C_MU_T c t alpha rng_alpha 1 mu mu_t mu pr_d mu_t mutmu_t alpha mu return pr_d DEFINE_SOURCE eps_r_source c t dS eqn 2 66 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros real con source real mu C_MU_L c t real mu_t C_MU_T c t real k C_K c t real d C_D c t real prod C_PRODUCTION c t real s sqrt prod mu mu_t real eta s k d real eta_O 4 38 real term mu_t s s s 1 0 0 012 eta etax eta source term 1 eta eta_0 dSleqn term d return source Hooking a Prandtl Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PRANDTL_K is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_k will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 14 Hooking DEFINE_PRANDTL UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 67 DEFINE Macros DEF INE_PRANDTL_O Description You can use DEFINE PRANDTL O to specify Prandtl numbers for specific dissipation w in the k w model Usage DEFINE_P
316. c when you want to loop over all cell threads in a given domain It consists of a single statement followed by the operation s to be performed on all cell threads in the domain enclosed within braces as shown below Note that thread_loop c is similar in implementation to the thread_loop_f macro described below Domain domain Thread c_thread thread_loop_c c_thread domain loops over all cell threads in domain Looping Over Face Threads in a Domain thread_loop _f You can use thread_loop f when you want to loop over all face threads in a given domain It consists of a single statement followed by the operation s to be performed on all face threads in the domain enclosed within braces as shown below Note that thread_loop_f is similar in implementation to the thread_loop_c macro described above Thread f_thread Domain domain thread_loop_f f_thread domain loops over all face threads in a domain 3 56 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros Looping Over Cells in a Cell Thread begin end_c_loop You can use begin_c_loop and end_c_loop when you want to loop over all cells in a given cell thread It contains a begin and end loop statement and performs operation s on each cell in the cell thread as defined between the braces This loop is usually nested within thread_loop_c when you want to loop over all cells in all cell threads in a domain cell_t c Thread c_th
317. cations However if your model requires custom transformations you can specify these matrices in your SDOF UDF First set the SDOF_CUSTOM_TRANS boolean to TRUE Then use the macros listed below to define custom coordination rotation and derivative rotation matrices CTRANS is the body global coordinate rotation matrix and DTRANS is the body global derivative rotation matrix SDOF_CUSTOM_TRANS boolean SDOF_CTRANS_11 coordinate rotation matrices SDOF_CTRANS_12 SDOF_CTRANS_13 SDOF_CTRANS_21 SDOF_CTRANS_22 SDOF_CTRANS_23 SDOF_CTRANS_31 SDOF_CTRANS_32 SDOF_CTRANS_33 SDOF_DTRANS_1i1 derivative rotation matrices SDOF_DTRANS_12 SDOF_DTRANS_13 SDOF_DTRANS_21 SDOF_DTRANS_22 SDOF_DTRANS_23 SDOF_DTRANS_31 SDOF_DTRANS_32 SDOF_DTRANS_33 2 222 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros Example 1 The following UDF named stage is a simple example of setting mass and moments of inertia properties for a moving object This UDF is typical for applications in which a body is dropped and the SDOF solver computes the body s motion in the flow field DRC I RK FK 2K 2K K FK 2K A 3K A K A 2k 2K 2k FK 2k K 2k 2K 2k K FK ak 2 K 2 2k K K Simple example of a SDOF property UDF for a moving body BORO o kkk kk k kkk kkk kk include udf h DEFINE_SDOF_PROPERTIES stage prop dt time dtime prop SDOF_MASS 800 0 prop SDOF_1IXXx 200 0 prop
318. ccess to a shared library 1 6 Hooking UDFs to Your ANSYS FLUENT Model After your UDF source file is interpreted or compiled the function s contained in the interpreted code or shared library will appear in drop down lists in graphical user in terface dialog boxes ready for you to activate or hook to your CFD model See Chapter 6 Hooking UDFs to ANSYS FLUENT for details on how to hook a UDF to ANSYS FLUENT 1 7 Mesh Terminology Most user defined functions access data from an ANSYS FLUENT solver Since solver data is defined in terms of mesh components you will need to learn some basic mesh terminology before you can write a UDF A mesh is broken up into control volumes or cells Each cell is defined by a set of nodes a cell center and the faces that bound the cell Figure 1 7 1 ANSYS FLUENT uses internal data structures to define the domain s of the mesh to assign an order to cells cell faces and nodes in a mesh and to establish connectivity between adjacent cells 1 8 Release 12 0 ANSYS Inc January 26 2009 1 7 Mesh Terminology A thread is a data structure in ANSYS FLUENT that is used to store information about a boundary or cell zone Cell threads are groupings of cells and face threads are groupings of faces Pointers to thread data structures are often passed to functions and manipulated in ANSYS FLUENT to access the information about the boundary or cell zones represented by each thread Each boundary or
319. ce s principal compute node inside your face looping macro using PRINCIPAL FACE P This is shown in the example below See Section 7 2 Cells and Faces in a Partitioned Mesh for details Example begin_f_loop f tf each compute node checks whether or not it is the principal compute node with respect to the given face and thread if PRINCIPAL_FACE_P f tf face is on the principal compute node so get the area and pressure vectors and compute the total area and pressure for the thread from the magnitudes F_AREA area f tf total_area NV_MAG area total_pres_a NV_MAG area F_P f tf end_f_loop f tf total_area PRF_GRSUM1 total_area total_pres_a PRF_GRSUM1 total_pres_a 7 5 6 Cell and Face Partition ID Macros In general cells and faces have a partition ID that is numbered from 0 to n 1 where n is the number of compute nodes The partition IDs of cells and faces are stored in the variables C_PART and F_PART respectively C_PART c tc stores the integer partition ID of a cell and F_PART tf stores the integer partition ID of a face 7 26 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Note that myid can be used in conjunction with the partition ID since the partition ID of an exterior cell is the ID of the neighboring compute node Cell Partition IDs For interior cells the partition ID is the same as the compute node ID For exterior cells the compute node
320. ce File Name imyworkfudfexample c CPP Command Name cpp Stack Size oo i ied io Display Assembly Listing Cluse Contributed CPP Figure 8 1 4 The Interpreted UDFs Dialog Box Release 12 0 ANSYS Inc January 26 2009 8 1 Step By Step UDF Example 2 In the Interpreted UDFs dialog box indicate the UDF source file you want to in terpret by clicking the Browse button This will open the Select File dialog box Figure 8 1 5 Select File Look in E 4 My Recent Documents Desktop My Documents kot on LEBKTHOMP UDF Source File udfexample c My Network Files of type UDF Source Files Figure 8 1 5 The Select File Dialog Box In the Select File dialog box select the desired file e g myexample c and click OK The Select File dialog box will close and the complete path to the file you selected will appear in the Source File Name text box in the Interpreted UDFs dialog box Figure 8 1 4 In the Interpreted UDFs dialog box specify the C preprocessor to be used in the CPP Command Name text box You can keep the default cpp or you can select Use Contributed CPP to use the preprocessor supplied by ANSYS FLUENT Keep the default Stack Size setting of 10000 unless the number of local variables in your function will cause the stack to overflow In this case set the Stack Size to a number that is greater than the number of local variables us
321. ce file can contain multiple concatenated functions Refer to Appendix A for basic information on C programming Below is an example of how the profile described in Step 1 can be implemented in a UDF The functionality of the UDF is designated by the leading DEFINE macro Here the DEFINE PROFILE macro is used to indicate to the solver that the code that follows will provide profile information at boundaries Other DEFINE macros will be discussed later in this manual See Chapter 2 DEFINE Macros for details about DEFINE macro usage POR O RCO kkk k kkk kkk kkk kkk kk kk kk k kkk k kk k I kk kk kk KK k kkk k A A kk kk kkk k kk 2k k myexample c UDF for specifying steady state velocity profile boundary condition EEEE ooo ooo 2 4 4 4 24 21 21 21 kkk k kkk kkk kk 2k 2k include udf h DEFINE_PROFILE inlet_x_velocity thread position real x ND_ND this will hold the position vector real y h face_t f h 0 016 inlet height in m begin_f_loop f thread 4 F_CENTROID x f thread y 2 x 1 0 5 h h non dimensional y coordinate F_PROFILE f thread position 0 1 1 0 y y Release 12 0 ANSYS Inc January 26 2009 8 1 Step By Step UDF Example end_f_loop f thread The first argument of the DEFINE_PROFILE macro inlet_x_velocity is the name of the UDF that you supply The name will appear in the boundary condition dialog box after the function is interpreted or compiled enabling y
322. ce_t f Thread t cell_t c0 Thread t0 real cid real cir B 2 Release 12 0 ANSYS Inc January 26 2009 B 2 Model Specific DEF INE Macro Definitions define DEFINE_NET_REACTION_RATE name c t particle pressure temp yi rr jac void name cell_t c Thread t Particle particle double pressure double temp double yi double rr double jac define DEFINE_NOX_RATE name c t Pollut Pollut_Par NOx void name cell_t c Thread t Pollut_Cell Pollut Pollut_Parameter Poll_Par NOx_Parameter NOx define DEFINE_PRANDTL_K name c t real name cell_t c Thread t define DEFINE_PRANDTL_D name c t real name cell_t c Thread t define DEFINE_PRANDTL_O name c t real name cell_t c Thread t define DEFINE_PRANDTL_T name c t real name cell_t c Thread t define DEFINE_PRANDTL_T_WALL name c t real name cell_t c Thread t define DEFINE_PROFILE name t i void name Thread t int i define DEFINE_PROPFRTY name c t real name cell_t c Thread t define DEFINE_PR_RATE name c t r mw ci p sf dif_index cat_index rr void name cell_t c Thread t Reaction r real mw real ci Tracked_Particle p real sf int dif_index int cat_index real rr define DEFINE_SCAT_PHASE_FUNC name c f real name real c real f define DEFINE_SOLAR_INTENSITY name sun_x sun_y sun_z S_hour S_minute real name real sun_x real sun_y real sun_z int S_hour int S_minute
323. center of the inlet which drops to zero at the walls Release 12 0 ANSYS Inc January 26 2009 8 17 Examples 9 84e 02 8 86e 02 7 87e 02 6 89e 02 5 9le 02 4 92e 02 3 94e 02 2 95e 02 1 97e 02 9 84e 03 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 5 Velocity Magnitude Contours for a Parabolic Inlet x Velocity 9 83e 02 8 97e 02 a ae 8 11e 02 ty 2 7 7 7 25e 02 f r F DE 6 386 02 A A se Pa S sale E dar e a a a a ah ee ote 5 53e 02 a a ae eee ee a ee aa a P Leret maaa a 3 81e 02 ns 9066202 ve mera ee a aA 2 09e 02 1 24e 02 Velocity Vectors Colored By Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 2 6 Velocity Vectors for a Parabolic Inlet x Velocity 8 18 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Transient Pressure Outlet Profile for Flow in a Tube In this example a temporally periodic pressure boundary condition will be applied to the outlet of a tube using a UDF The pressure has the form Pz Po Asin wt The tube is assumed to be filled with air with a fixed total pressure at the inlet The pressure of the air fluctuates at the outlet about an equilibrium value po of 101325 Pa with an amplitude of 5 Pa
324. cific Heat ikg mass weighted mixing law Thermal Conductivity w m k Toss AE Vapor Particle Equilibrium eA raoult_vpe libudf v e Delete Close Help Figure 6 4 16 The Create Edit Materials Dialog Box 6 80 Release 12 0 ANSYS Inc January 26 2009 6 5 Hooking Dynamic Mesh UDFs Select user defined from the drop down list for Vapor Particle Equilibrium in the Proper ties group box This will open the User Defined Functions dialog box Select the UDF name e g raoult_vp libudf from the list of UDFs displayed and click OK Then click Change Create in the Create Edit Materials dialog box User Defined Fu raoult_vpe libudf Figure 6 4 17 The User Defined Functions Dialog Box See Section 2 5 15 DEFINE_DPM_VP_EQUILIB for details about DEFINE_DPM_VP_EQUILIBRIUM functions 6 5 Hooking Dynamic Mesh UDFs This section contains methods for hooking UDFs to ANSYS FLUENT that have been defined using DEFINE macros described in Section 2 6 Dynamic Mesh DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 5 1 Hooking DEFINE_CG_MOTION UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE_CG_MOTION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones dialog box Figure 6 5 1 To hook the UDF to ANSYS FLUENT you will first need
325. ck the Source Terms tab This will display the momentum source term parameters in the scrollable window Then click the Edit button next to the X Momentum source term to open the X Momentum sources dialog box Figure 8 2 14 Release 12 0 ANSYS Inc January 26 2009 8 27 Examples X Momentum n m3 sources Number of x Momentum n m3 sources 4 a udF cell_x_source x Figure 8 2 14 The X Momentum sources Dialog Box Enter 1 for the Number of Momentum sources in the X Momentum sources dialog box and then select the function name for the UDF udf cell_x source in the drop down list that appears Note that the name that is displayed in the drop down lists is your UDF name preceded by the word udf Click OK to accept the new cell zone condition and close the dialog box The X Momentum parameter in the Fluid dialog box will now display 1 source Click OK to fix the new momentum source term for the solution calculation and close the Fluid dialog box After the solution has converged you can view contours of static temperature to see the cooling effects of the wall on the liquid metal as it moves through the duct Figure 8 2 15 Contours of velocity magnitude Figure 8 2 16 show that the liquid in the cool region near the wall has indeed come to rest to simulate solidification taking place 8 28 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples 2 90e 02 2 90e 02 2
326. cosity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE TURBULENT VISCOSITY is interpreted Chapter 4 Interpreting UDF s or compiled Chapter 5 Compiling UDFs the function name s that you specified in the DEFINE macro argument s for example user_mu_t for single phase or mu_t_ke_mixture mu_t_ke_1 and mu_t_ke_2 for multiphase will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 26 Hooking DEFINE_TURBULENT_VISCOSITY UDFs for details 2 1 28 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 27 DEFINE_VR_RATE Description You can use DEFINE _VR_RATE to specify a custom volumetric reaction rate for a single reaction or for multiple reactions During ANSYS FLUENT execution DEFINE _VR_RATE is called for every reaction in every single cell A DEFINE_VR_RATE UDF is compatible with the laminar finite rate model but you must make sure that the stiff chemistry option is disabled Usage DEFINE_VR_RATE name c t r mw yi rr rr_t Argument Type Description symbol name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the volumetric reaction rate is to be applied Reaction r Pointer to data structure that represents the current reaction real mw Pointer to array of species molecular weights real yi Pointer to array of the species mass fractions real rr Pointer to laminar reaction rate real rr_t P
327. cosity computed by the function The value of the temperature is checked and based upon the range into which it falls the appropriate value of mu_lam is computed At the end of the function the computed value for the viscosity mu_lam is returned to the solver Release 12 0 ANSYS Inc January 26 2009 2 91 DEFINE Macros Example 2 User defined Mixing Law for Thermal Conductivity You can use DEFINE_PROPERTY to define custom user defined mixing laws for density viscosity and conductivity of mixture materials In order to access species material properties your UDF will need to utilize auxiliary utilities that are described above The following UDF named mass_wtd_k is an example of a mass fraction weighted con ductivity function The UDF utilizes the generic_property function to obtain properties of individual species It also makes use of MATERIAL_PROPERTY and THREAD_MATERIAL PK K ak kk 3k 2k k ak 2k akak 3k 2k 2k ak 3k 2k K 3K 2K 2K O FK 2K 2K K FK 2K 2K FK 2K 2K K FK 2K 2K K FK 2K K FK 2K 2K 2K FK 2K 2K FK FK 2K K FK FK 2K K FK 2K 2K K FK gt K UDF that specifies a custom mass fraction weighted conductivity EEEE ooo o kkk kkk kkk kkk kkk kkk include udf h DEFINE_PROPERTY mass_wtd_k c t real sum 0 int i Material sp real ktc Property prop mixture_species_loop THREAD_MATERIAL t sp i prop MATERIAL_PROPERTY sp ktc generic_property c t prop PROP_ktc C_T c t sum C_YI c t i k
328. cular_weight MIXTURE_speed_of_sound speed_of_sound MIXTURE_viscosity viscosity MIXTURE_thermal_conductivity thermal_conductivity MIXTURE_rho_t drho dT const p MIXTURE_rho_p drho dp const T MIXTURE_enthalpy_t dh dT const p MIXTURE_enthalpy_p dh dp const T DOR COO OOO OO EE E k k kk kkk k kkk k kkk kkk 2k kkk 2k kkk kkk paaa E OO A k k k kkk kkk k kkk kkk 2k kkk 2k kkk kkk UDRGM Example Real Gas Model with Volumetric Reactions This is an example of a UDRGM that has been set up for reacting flow simulations The example UDF code consists of the following sections e Definitions and constants for the physical properties of the species in the single step methane air reaction mixture CH4 O2 N2 CO2 H20 e Functions of the Redlich Kwong equation of state for the individual species property calculations e Functions for the mixture properties In this example the mixture properties are computed assuming ideal gas mixing rules In the UDRGM only the mixture species and associated properties are de fined No information about the chemical reactions is required in the UDF The chemical reaction is set up in a separate step after the UDF has been compiled and loaded into ANSYS FLUENT See Section 15 1 3 Defining Reactions in the separate User s Guide for details Release 12 0 ANSYS Inc January 26 2009 8 75 Examples xsccs id real_ideal c 1 10 Co
329. custom rate select Replace FLUENT Rate in the UDF Rate group box and click Apply Unless specifically defined in your SO rate UDF data and parameter settings will be derived from the settings in the SOx Model dialog box Therefore it is good practice to make the appropriate settings in the SOx Model dialog box even though you may use a UDF to replace the default rates with user specified rates There is no computational penalty for doing this because the default rate calculations will be ignored when Replace FLUENT Rate is selected To specify a custom maximum limit Timax for the integration of the temperature PDF for each cell you must first select the UDF name e g user_sox libudf from the SOx Rate drop down list as described previously Then select either temperature or tempera ture species from the PDF Mode drop down list in the Turbulence Interaction Mode group box Finally select user defined from the Tmax Option drop down list and click Apply See Section 2 3 20 DEFINE SOX RATE for details about defining DEFINE_SOX_RATE func tions 6 44 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs SOx Model Figure 6 2 28 The SOx Model Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 45 Hooking UDFs to ANSYS FLUENT 6 2 21 Hooking DEFINE_SPECIFIC_HEAT UDFs After you have compiled your DEFINE_SPECIFIC_HEAT UDF as described in Chapter 5 Com piling UDFs the name of the func
330. d k epsilon formulation EEEE ooo o kkk k k kkk kkk kk kkk k kkk include udf h DEFINE_TURBULENT_VISCOSITY user_mu_t c t real mu_t real rho C_R c t real k C_K c t real d C_D c t mu_t M_keCmu rho SQR k d return mu_t Example 2 Multiphase Turbulent Viscosity UDF pE aaao oo ooo o o kkk kk CA A A A A kk kk kkk Custom turbulent viscosity functions for each phase and the mixture in a two phase multiphase flow BOA ooo o kkk kk kkk kkk kkk kk kkk include udf h DEFINE_TURBULENT_VISCOSITY mu_t_ke_mixture c t real mu_t real rho C_R c t real k C_K c t real d C_D c t real cmu M_keCmu mu_t rho cmu xk k d return mu_t DEFINE_TURBULENT_VISCOSITY mu_t_ke_1 c t Thread tm lookup_thread_by_id DOMAIN_SUPER_DOMAIN THREAD_DOMAIN t Release 12 0 ANSYS Inc January 26 2009 2 1 27 DEFINE Macros t gt id CACHE_T_SV_R density t SV_DENSITY CACHE_T_SV_R mu_t t SV_MU_T CACHE_T_SV_R density_m tm SV_DENSITY CACHE_T_SV_R mu_t_m tm SV_MU_T return density c density_m c mu_t_m c DEFINE_TURBULENT_VISCOSITY mu_t_ke_2 c t Thread tm lookup_thread_by_id DOMAIN_SUPER_DOMAIN THREAD_DOMAIN t t gt id CACHE_T_SV_R density t SV_DENSITY CACHE_T_SV_R mu_t t SV_MU_T CACHE_T_SV_R density_m tm SV_DENSITY CACHE_T_SV_R mu_t_m tm SV_MU_T return density c density_m c mu_t_m c Hooking a Turbulent Vis
331. d Chap ter 5 Compiling UDFs the name that you specified in the DEFINE macro argument e g my_user_cp will become visible and selectable in the Create Edit Materials dialog box in ANSYS FLUENT See Section 6 2 21 Hooking DEFINE SPECIFIC HEAT UDFs for details 2 3 22 DEFINE_SR_RATE Description You can use DEFINE_SR_RATE to specify a custom surface reaction rate A custom sur face reaction rate function defined using this macro will overwrite the default reaction rate e g finite rate that is specified in the Create Edit Materials dialog box A DEFINE_VR_RATE UDF is compatible with the laminar finite rate model but you must make sure that the stiff chemistry option is disabled An example of a reaction rate that depends upon gas species mass fractions is provided below Also provided is a reaction rate UDF that takes into account site species Note that the three types of surface reaction species are internally num bered with an integer index i in order 2 1 14 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Usage DEFINE SR_RATE name f t r my yi rr Argument Type Description symbol name UDF name face_t f Index that identifies a face within the given thread or cell in the case of surface reaction in a porous zone Thread t Pointer to face thread on which the surface rate reaction is to be applied Reaction r Pointer to data structure for the reaction real mw Pointer to arr
332. d a cell index c and cell thread pointer tc In most situations there is no need to use the exterior cell loop macros They are only provided for convenience if you come across a special need in your UDF Release 12 0 ANSYS Inc January 26 2009 7 23 Parallel Considerations begin_c_loop_ext c tc end_c_loop_ext c tc Figure 7 5 2 Looping Over Exterior Cells in a Partitioned Mesh Using begin end_c_loop ext indicated by the green cells Interior and Exterior Cell Looping Macro The macro begin end_c_loop can be used in a serial or parallel UDF In parallel the macro will loop over all interior and exterior cells in a mesh partition Figure 7 5 3 Note that in serial this pair of macros is equivalent to the begin end_c_loop_int macros It contains a begin and end statement and between these statements operations can be performed on each of the thread s interior and exterior cells in turn The macro is passed a cell index c and a cell thread pointer tc begin_c_loop c tc end_c_loop c tc 7 24 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Figure 7 5 3 Looping Over Both Interior and Exterior Cells in a Partitioned Mesh Using begin end_c_loop Example real temp begin_c_loop c tc get cell temperature compute temperature function and store result in user defined memory location index 0 temp C_T c tc C_UDMI c tc 0 temp tmin tmax t
333. d assign the global domain pointer by executing the DEFINE_ON_DEMAND function paaa k kk kkk kkk kkk kkk k kk kkk kkk k kk k k kkk k kk kk k kkk A A k kk kk kk k k k kk k UDF for extending postprocessing of wall impacts EEEE ooo oo oo o kkk 2k 1 1 2 2 kkk 2k 2k include udf h define MIN_IMPACT_VELO 1000 Minimum particle velocity normal to wall m s to allow Accretion Domain domain Get the domain pointer and assign it later to domain 2 1 68 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros enum Enumeration of used User Defined Memory Locations NUM_OF_HITS Number of particle hits into wall face considered AVG_DIAMETER Average diameter of particles that hit the wall AVG_RADI_VELO Average radial velocity of NUM_OF_USED_UDM int UDM_checked 0 Availability of UDMLs checked void reset_UDM_s void Function to follow below int check_for_UDM void Check for UDMLs availability Thread t if UDM_checked return UDM_checked if rp_axi Internal_Error UDF Error only valid for 2d axisymmetric cases n thread_loop_c t domain We require all cell threads to provide space in memory for UDML if FLUID_THREAD_P t if NULLP THREAD_STORAGE t SV_UDM_I return 0 UDM_checked 1 To make the following work properly reset_UDM_s This line
334. d click OK Next open the Materials task page lt DUECO Select one of the materials in the Materials list and click Create Edit to open the Create Edit Materials dialog box Figure 6 6 1 6 90 Release 12 0 ANSYS Inc January 26 2009 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs Create Edit Materials Name D Material Type Fluid Order Materials by Name v O Chemical Formula Chemical Formula FLUENT Fluid Materials Properties Cp Specific Heat j kg k air J FLUENT Database none constant 1006 43 Thermal Conductivity wim k constant 0 0242 viscosity kg m s constant 1 7894e 05 UDS Diffusivity kg m s ce as v ed es User Defined Database v Figure 6 6 1 The Create Edit Materials Dialog Box Scroll down the Properties group box in the Create Edit Materials dialog box Figure 6 6 1 and select defined per uds from the UDS Diffusivity drop down list This will open the UDS Diffusion Coefficients dialog box Figure 6 6 2 Release 12 0 ANSYS Inc January 26 2009 6 91 Hooking UDFs to ANSYS FLUENT UDS Diffusion Coefficients User Defined Scalar Diffusion _ Coefficient user defined anisotropic cyl_ortho_difF slibudF Figure 6 6 2 The UDS Diffusion Coefficients Dialog Box In th
335. d for in the turbulence interaction mod eling You can calculate a custom maximum limit Tmax for each cell and then assign it to the POLLUT_CTMAX Pollut_Par macro see Section 3 2 7 SO Macros for further details about data access macros Example 2 demonstrates this use of DEFINE_SOX_RATE Fa If you want to use DEFINE_SOX_RATE only for the purpose of specifying Tmax be sure that the user defined SO rate does not alter the internally calculated rate for the source term calculation Usage DEFINE SOX RATE name c t Pollut Pollut Par SOx Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the SO rate is to be applied Pollut_Cell Pollut Pointer to the data structure that contains the common data at each cell Pollut_Parameter Pollut_Par Pointer to the data structure that contains auxiliary data SOx_Parameter SOx Pointer to the data structure that contains data specific to the SOx model Function returns void 2 1 06 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros There are six arguments to DEFINE_SOX_RATE name c t Pollut Pollut_Par and SOx You will supply name the name of the UDF c t Pollut Pollut_Par and SOx are variables that are passed by the ANSYS FLUENT solver to your function A DEFINE SOX RATE function does not output a value The calculated SO rates or other pollutant species rates are returned through th
336. d in Sec tion 1 10 1 Multiphase specific Data Types if the subthread pointer is associated with an inlet zone then the macro will provide the pointers to the face threads associated with the inlet for each of the phases int phase_domain_index Thread subthread Thread mixture_thread sub_thread_loop subthread mixture_thread phase_domain_index The variable arguments to sub_thread_loop are subthread mixture_thread and phase_domain_index subthread is a pointer to the phase thread and mixture_thread is a pointer to the mixture level thread The mixture_thread is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a thread variable argument e g DEFINE_PROFILE and your UDF is hooked to the mix ture If the mixture_thread is not explicitly passed to your UDF you will need to use a utility macro to retrieve it before calling sub_thread_loop phase_domain_index is an index of subdomain pointers that can be retrieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details The index begins at 0 for the primary phase and is incremented by one for each secondary phase in the mixture Note that subthread and phase_domain_index are initialized within the sub_thread_loop macro definition Looping Over Phase Cell Threads in Mixture mp_thread_loop_c The mp_thread_loop_c macro loops through all cell threads at the mixture level within
337. d to compute the real property only for a single cell and return it to the solver Note that like source term UDFs property UDFs defined using DEFINE_PROPERTY are called by ANSYS FLUENT from within a loop on cell threads The solver passes all of the variables needed to allow a DEFINE_PROPERTY UDF to define a custom material since properties are assigned on a cell basis Consequently your UDF will not need to loop over cells in a zone since ANSYS FLUENT is already doing it Auxiliary Utilities Some commonly used auxiliary utilities for custom property UDFs are described below They are generic_property MATERIAL_PROPERTY THREAD MATERIAL and mixture_species_loop generic_property is a general purpose function that returns the real value for the given property id for the given thread material It is defined in prop h and is used only for species properties The following Property_ID variables are available e PROP_rho density e PROP_mu viscosity e PROP ktc thermal conductivity generic property name c t prop id T Argument Type Description symbol name Function name cell t Cell index Thread t Pointer to cell thread on which property function is to be applied Property prop Pointer to property array for the thread material that can be obtained through the macro MATERIAL_PROPERTY m See below Property ID id Property ID of the required property you want to define a custom mixing law for e g PROP_ktc for therm
338. d using DEFINE_EMISSIVITY_WEIGHTING_FACTOR is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g em wt will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 7 Hooking DEFINE_EMISSIVITY_WEIGHTING_FACTOR UDFs for details 2 3 8 DEFINE_GRAY_BAND_ABS_COEFF Description You can use DEFINE GRAY BAND _ABS_COEFF to specify a UDF for the gray band absorp tion coefficient as a function of temperature that can be used with a non gray discrete ordinates model Usage DEFINE GRAY BAND_ABS_COEFF name c t nb Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread int nb Band number associated with non gray model Function returns real There are four arguments to DEFINE_GRAY_BAND_ABS_COEFF name c t and nb You supply name the name of the UDF The variables c t and nb are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value of the gray band coefficient to the solver Example The following UDF named user_gray_band_abs specifies the gray band absorption co efficient as a function of temperature that can be used for a non gray discrete ordinates model Release 12 0 ANSYS Inc January 26 2009 2 43 DEFINE Macros include udf h DEFINE_GRAY_BAND_ABS_COEF
339. dary of the domain except for symmetric or periodic boundaries You can define a separate UDF using DEFINE_DPM_BC for each boundary Usage DEFINE DPM BC name p t f f normal dim Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Thread t Pointer to the face thread the particle is currently hitting face_t f Index of the face that the particle is hitting real f normal Array that contains the unit vector which is normal to the face int dim Dimension of the flow problem The value is 2 in 2d for 2d axisymmetric and 2d axisymmetric swirling flow while it is 3 in 3d flows Function returns int There are six arguments to DEFINE_DPM_BC name p t f f normal and dim You supply name the name of the UDF p t f f normal and dim are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the new velocity of a particle after hitting the wall and then return the status of the particle track as an int after it has hit the wall i Pointer p can be used as an argument to the particle specific macros de fined in Section 3 2 7 DPM Macros to obtain information about particle properties Example 1 This example shows the usage of DEFINE DPM BC for a simple reflection at walls It is similar to the reflection method executed by ANSYS FLUENT except that ANSY
340. data and UDF source files in the Working Directory text box in the General Options tab e If you plan to compile the UDF make sure that the batch file for the UDF compilation environment settings is correctly specified in the UDF Compiler tab see Section 5 1 2 Compilers for further details 2 Read or set up your case file Release 12 0 ANSYS Inc January 26 2009 8 5 Examples 8 1 5 Step 4 Interpret or Compile the Source File You are now ready to interpret or compile the profile UDF named inlet_x_velocity that you created in Step 2 and is contained within the source file named myexample c In general you must compile your function as a compiled UDF if the source code contains structured reference calls or other elements of C that are not handled by the ANSYS FLUENT interpreter To determine whether you should compile or interpret your UDF see Section 1 5 1 Differences Between Interpreted and Compiled UDFs Interpret the Source File Follow the procedure below to interpret your source file in ANSYS FLUENT For more information on interpreting UDFs see Chapter 4 Interpreting UDFs Note that this step does not apply to Windows parallel networks See Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box for details 1 Open the Interpreted UDFs dialog box Define gt User Defined Functions Interpreted Interpreted UDFs Sour
341. data types represent the computational units for a mesh Figure 1 7 1 Variables that are defined using these data types are typically supplied as arguments to DEFINE macros as well as to other special functions that access ANSYS FLUENT solver data Some of the more commonly used ANSYS FLUENT data types are Node face_t cell _t Thread Domain Node is a structure data type that stores data associated with a mesh point face_t is an integer data type that identifies a particular face within a face thread cell_t is an integer data type that identifies a particular cell within a cell thread Thread is a structure data type that stores data that is common to the group of cells or faces that it represents For multiphase applications there is a thread structure for each phase as well as for the mixture See Section 1 10 1 Multiphase specific Data Types for details Domain is a structure data type that stores data associated with a collection of node face and cell threads in a mesh For single phase applications there is only a single domain structure For multiphase applications there are domain structures for each phase the interaction between phases as well as for the mixture The mixture level domain is the highest level structure for a multiphase model See Section 1 10 1 Multiphase specific Data Types for details 1 10 Release 12 0 ANSYS Inc January 26 2009 1 8 Data Types in ANSYS FLUENT i Note that all of the ANSY
342. dditional Macros for Writing UDFs Table 3 2 13 Macros for Cell Velocity Derivatives Defined in mem h Macro Argument Types Returns C_STRAIN_RATE_MAG c t cell_t c Thread t strain rate magnitude C_DUDX c t cell_t c Thread t velocity derivative C_DUDY c t cell t c Thread t velocity derivative C_DUDZ c t cell_t c Thread t velocity derivative C_DVDX c t cell_t c Thread t velocity derivative C DVDY Ce t cell_t c Thread t velocity derivative C_DVDZ c t cell_t c Thread t velocity derivative C_DWDX c t cell t c Thread t velocity derivative C_DWDY c t cell t c Thread t velocity derivative C_DWDZ c t cell_t c Thread t velocity derivative Material Property Macros The macros listed in Tables 3 2 14 3 2 16 can be used to return real material property variables in SI units The variables are available in both the pressure based and the density based solver Argument real prt is the turbulent Prandtl number Definitions for material property macros can be found in the referenced header file e g mem h 3 18 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Table 3 2 14 Macros for Diffusion Coefficients Defined in mem h CKT c t prt CKEFF c t prt C_DIFF_L c t i j C_DIFF_EFF c t i cell_t c Thread t real prt cell_t c Thread t real prt cell_t c Thread t int i int j cell t c Thread t int i Macro Argument Types
343. de 3ddp_host or 3ddp_node Release 12 0 ANSYS Inc January 26 2009 5 13 Compiling UDFs PARALLEL NODE the parallel communications library Specify none for a serial version of the solver or one of the following smpi parallel using shared memory for multiprocessor machines vmpi parallel using shared memory or network with vendor MPI software net parallel using network communicator with RSHD software i If you are using a parallel version of the solver be sure to edit both copies of user_nt udf the one in the host folder and the one in the node folder and specify the appropriate SOURCE VERSION and PARALLEL_NODE in each file Set PARALLEL_NODE none for the host version and one of the other options smpi vmpi net nmpi for the node version depending on which message passing method you are going to use An excerpt from a sample user_nt udf file is shown below Replace text in and remove quotes indicates a choice note SRC is defined in the makefile SOURCES SRC udfexample c VERSION 2d PARALLEL_NODE none 2 In the Visual Studio command prompt window go to each version folder e g libudf ntx86 2d and type nmake as shown in the following example C users user_name work_dir libudf ntx86 2d gt nmake The following messages will be displayed Microsoft R Program Maintenance Utility Version 7 10 3077 Copyright C Microsoft Corporation All rights reserved cl c Za DUDF_EX
344. de for more details The radiative wall heat flux can be given by Equation 8 2 9 q TVG a 8 2 8 Ew an Bas 40T Gu 8 2 9 arw This form of the boundary condition is unfortunately specified in terms of the incident radiation at the wall Gwu This mixed boundary condition can be avoided by solving first for Gu using Equations 8 2 8 and 8 2 9 resulting in Equation 8 2 10 Then this Release 12 0 ANSYS Inc January 26 2009 8 43 Examples expression for Gay is substituted back into Equation 8 2 9 to give the radiative wall heat flux qrw as Equation 8 2 11 40T hE wy F Go Fo G Ep Gu 8 2 10 aolo Ew A Ey 0 qr 4r Io Tiw Go bo G 8 2 11 The additional 6o and Go terms that appear in Equations 8 2 10 and 8 2 11 are a result of the evaluation of the gradient of incident radiation in Equation 8 2 8 In ANSYS FLUENT the component of a gradient of a scalar directed normal to a cell boundary face VG n is estimated as the sum of primary and secondary components The primary component represents the gradient in the direction defined by the cell cen troids and the secondary component is in the direction along the face separating the two cells From this information the face normal component can be determined The secondary component of the gradient can be found using the ANSYS FLUENT macro BOUNDARY_SECONDARY_GRADIENT_SOURCE which is described in Section 3 2 5 Bou
345. de your release area but do not remove an old copy of udf h from your working folder you will not be accessing the most recent version of this file Ez You should not under any circumstances alter the udf h file 4 1 2 Limitations Due to limitations in the interpreter used to compile interpreted UDF source code in AN SYS FLUENT interpreted UDFs are limited in their use of the C programming language In particular the following elements of C cannot be used in interpreted UDFs e goto statements e non ANSI C prototypes for syntax e direct data structure references e declarations of local structures e unions e pointers to functions e arrays of functions e multi dimensional arrays Release 12 0 ANSYS Inc January 26 2009 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box This section presents the steps for interpreting a source file in ANSYS FLUENT After it has been interpreted the names of UDFs contained within the source file will appear in drop down lists in graphics dialog boxes in ANSYS FLUENT The general procedure for interpreting a source file is as follows 1 Make sure that the UDF source file is in the same folder that contains your case and data files If you are running the parallel version of ANSYS FLUENT on a network of Windows machines you must share the working folder that contains your UDF
346. definitions for ANSYS FLUENT constructs such as Domain You must NOT reference any ANSYS FLUENT globals directly from within this module nor link this against any ANSYS FLUENT libs doing so will cause dependencies on a specific ANSYS FLUENT binary such as f1551 exe and thus won t be version independent include udf h include stdio h include ctype h include stdarg h if RP_DOUBLE define SMALL 1 e 20 else define SMALL 1 e 10 endif define NCMAX 20 define NSPECIE_NAME 80 static int usersMessage char static void usersError char static double ref_p ref_T static char gas NCMAX NSPECIE_NAME static int n_Specs 8 66 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double Mixture_Rgas double yil double Mixture_pressure double Temp double Rho double yil double Mw_i int i double Cp_i double T double r int i double K_i double T double r int i double Mu_i double T double r int i double Rgas_i double T double r int i double Gm_i double T double r int i DEF INE_ON_DEMAND I_do_nothing This is a dummy function must be included to allow for the use of the ANSYS FLUENT UDF compilation utility void Mixture_error int err char f char msg if err usersError Mixture_error 4d from function s nz s n err f msg DCO OOO AO ASIII I A A A Ak 2k 3k 2k 2k 2k ak Mixture Function
347. dialog box Figure 6 2 16 in ANSYS FLUENT Were Were Edit Viscous Model Model Model Constants O Inviscid O Laminar Spalart Allmaras 1 eqn k epsilon 2 eqn C1 Epsilon O k omega 2 eqn 1 44 Transition k kl omega 3 eqn O Transition SST 4 eqn O Reynolds Stress 7 eqn Detached Eddy Simulation Large Eddy Simulation LES _ TOR Prandtl Number C2 Epsilon 1 92 k epsilon Model 1 3 Standard ORNG User Defined Functions O Realizable Turbulent Viscosity Near Wall Treatment none Standard Wall Functions Prandtl and Schmidt Numbers O Non Equilibrium Wall Functions TKE Prandtl Number Enhanced Wall Treatment peu a User Defined Wall Functions per Dt Ai C 1 TDR Prandtl Number none v Options viscous Heating Energy Prandtl Number none Figure 6 2 16 The Viscous Model Dialog Box To hook the UDF to ANSYS FLUENT select the function name e g user_pr_k libudf from the TKE Prandtl Number drop down list under User Defined Functions in the Viscous Model dialog box and click OK See Section 2 3 14 DEFINE PRANDTL UDFs for details about DEFINE_PRANDTL functions Release 12 0 ANSYS Inc January 26 2009 6 31 Hooking UDFs to ANSYS FLUENT 6 2 15 Hooking DEFINE_PROFILE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_
348. dition cell zone condition cell zone condition cell zone condition SOx Model Create Edit Materials User Defined Function Hooks Viscous Model User Defined Function Hooks Viscous Model Viscous Model User Defined Function Hooks Viscous Model Release 12 0 ANSYS Inc January 26 2009 2 29 DEFINE Macros 2 30 Table 2 3 5 Quick Reference Guide for Model Specific DEFINE Functions MULTIPHASE ONLY Function DEFINE Macro Dialog Box Activated In volume fraction all multiphase models contact angle VOF heat transfer coefficient Eulerian surface tension coefficient VOF cavitation surface tension coefficient Mixture cavitation vaporization pressure Mixture particle or droplet diameter Mixture diameter Eulerian Mixture solids pressure Eulerian Mixture radial distribution Eulerian Mixture elasticity modulus Eulerian Mixture viscosity Eulerian Mixture temperature Eulerian Mixture bulk viscosity Eulerian frictional viscosity Eulerian frictional pressure Eulerian frictional modulus Eulerian granular viscosity Eulerian granular bulk viscosity Eulerian granular conductivity Eulerian temperature source Eulerian Mixture DEFINE_PROFILE DEFINE PROFILE DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF
349. down list under User Defined Functions in the Viscous Model dialog box and click OK Release 12 0 ANSYS Inc January 26 2009 6 51 Hooking UDFs to ANSYS FLUENT i The Species Transport model must be selected in the Species Model dialog box for the Turbulent Schmidt Number drop down list to be visible in the Viscous Model dialog box See Section 2 3 25 DEFINE _TURB SCHMIDT UDF for details about DEFINE_TURB_SCHMIDT functions 6 2 26 Hooking DEFINE_TURBULENT_VISCOSITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_TURBULENT_VISCOSITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model dialog box Figure 6 2 35 in ANSYS FLUENT ree Were Edit Viscous Model Model Model Constants O Inviscid O Laminar Spalart Allmaras 1 eqn O k epsilon 2 eqn Ok omega 2 eqn O Transition k kl omega 3 eqn O Transition SST 4 eqn O Reynolds Stress 7 eqn Detached Eddy Simulation O Large Eddy Simulation LES Spalart Allmaras Production Vorticity Based OStrainjVorticity Based User Defined Functions Turbulent Viscosity Spalart Allmaras Options user_mu_t slibudF v Low Re Damping Options C viscous Heating Figure 6 2 35 The Viscous Model Dialog Box To hook the UDF to ANSYS FLUENT select the func
350. e Usage DEFINE_DPM_HEAT_MASS name p C_p hgas hvap cvap_surf Z dydt dzdt Argument Type symbol name Tracked_Particle p real C_p real hgas real hvap real cvap_surf real Z real dydt dpms_t dzdt Function returns void There are eight arguments Description UDF name Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked Particle heat capacity Enthalpies of vaporizing gas phase species Vaporization enthalpies of vaporizing components Vapor equilibrium concentrations of vaporizing components Compressibility ZY Source terms of the particle temperature and component masses Source terms of the gas phase enthalpy and species masses to DEFINE_DPM_HEAT_MASS name e p C_p hgas hvap cvap_surf dydt and dzdt You supply name the name of the UDF e p C_p hgas hvap and cvap_surf are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the part and dzdt respectively Example icle and gas phase source terms and store the values in dydt The following is an example of a compiled UDF that uses DEFINE_DPM_HEAT_MASS It implements the source ter Source Term particle temperature particle component mass gas phase enthalpy gas phase species mass Release 12 0 ANSYS Inc January 26 ms for the following Variable Unit dydt 0 K s dydt 1 kg s dzdt gt energy J s dzdt gt species 0 kg s 200
351. e integer number of memory locations used It is defined in models h Data_Valid_P You can check that the cell values of the variables that appear in your UDF are accessible before you use them in a computation by using the Data_Valid_P macro cxboolean Data_Valid_P Data Valid P is defined in the id h header file and is included in udf h The function returns 1 true if the data that is passed as an argument is valid and 0 false if it is not Example if Data_Valid_P return 3 80 Release 12 0 ANSYS Inc January 26 2009 3 8 Miscellaneous Macros Suppose you read a case file and in the process load a UDF If the UDF performs a calculation using variables that have not yet been initialized such as the velocity at interior cells then an error will occur To avoid this kind of error an if else condition can be added to your code If if the data are available the function can be computed in the normal way If the data are not available else then no calculation or a trivial calculation can be performed instead After the flow field has been initialized the function can be reinvoked so that the correct calculation can be performed FLUID_THREAD_P cxboolean FLUID_THREAD_P t You can use FLUID_THREAD _P to check whether a cell thread is a fluid thread The macro is passed a cell thread pointer t and returns 1 or TRUE if the thread that is passed is a fluid thread and 0 or FALSE if it is not
352. e udf h DEFINE_PROFILE q_ni t position real A 3 e_n 3 face_t f real At begin_f_loop f t F_AREA A f t At NV_MAG A NV_VS e_n A At F_PROFILE f t position e_n 0 end_f_loop f t DEFINE_PROFILE q_nj t position real A 3 e_n 3 face_t f real At begin_f_loop f t F_AREA A f t At NV_MAG A NV_VS e_n A At F_PROFILE f t position e_n 1 end_f_loop f t 2 82 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros DEFINE_PROFILE q_nk t position real A 3 e_n 3 face_t f real At begin_f_loop f t F_AREA A f t At NV_MAG A NV_VS e_n A At F_PROFILE f t position e_n 2 end_f_loop f t Example 6 Viscous Resistance Profile in a Porous Zone You can either use F_PROFILE or C_PROFILE to define a viscous resistance profile in a porous zone Below are two sample UDFs that demonstrate the usage of F_PROFILE and C_PROFILE respectively Note that porosity functions are hooked to ANSYS FLUENT in the Porous Zone tab in the appropriate Fluid cell zone conditions dialog box The following UDF named vis_res generates a viscous resistance profile in a porous zone After it has been interpreted or compiled and loaded you can activate this UDF in the Fluid cell zone condition dialog box in ANSYS FLUENT Viscous Resistance Profile UDF in a Porous Zone that utilizes F_PROFILE include udf h DEFI
353. e 3 2 11 to allow access to the value of the variable at the time step before the previous one i e t 2At These data may be useful in unsteady simulations For example C_T_M2 c t returns the value of the cell temperature at the time step before the previous one re ferred to as second previous time step Two previous time step macros are shown in Table 3 2 12 i Note that data from C_T_M2 is available only if user defined scalars are defined It can also be used with adaptive time stepping Table 3 2 12 Macros for Cell Time Level 2 Defined in mem h Macro Argument Types Returns CRM2 c t cell_t c Thread t density second previous time step C_P_M2 c t cell_t c Thread t pressure second previous time step CUM2 c t cell_t c Thread t velocity second previous time step C_V_M2 c t cell_t c Thread t velocity second previous time step C_W_M2 c t cell t c Thread t velocity second previous time step C_T_M2 c t cell_t c Thread t temperature second previous time step C_YIM2 c t i cell_t c Thread t int i species mass fraction second previous time step Derivative Macros The macros listed in Table 3 2 13 can be used to return real velocity derivative variables in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in the mem h header file Release 12 0 ANSYS Inc January 26 2009 3 17 A
354. e File 1 5 1 5 Interpreting and Compiling UDFs 46 44 4 448 eee Gea bo 1 6 1 5 1 Differences Between Interpreted and Compiled UDFs 1 7 1 6 Hooking UDFs to Your ANSYS FLUENT Model 1 8 Li Mesh Terminology 45 4 lt 4 244 444844 eed 4 bee 244448 S 1 8 18 Data Typee in ANSYS FLUENT o s sice de sosta po sie wR a 1 10 1 9 UDF Calling Sequence in the Solution Process oaa 1 12 1 10 Special Considerations for Multiphase UDFs 1 17 1 10 1 Multiphase specific Data Types o 24 56 aa ek ee es 1 17 2 DEFINE Macros 2 1 21 Dniodu ction 2 2 6 8 2 oe kOe ewe KEG Ee EME Meee OHSS SE 2 1 2 2 General Purpose DEFINE Macros 22 4 ie eee be ee ee ee Es 2 2 22 1 DEFINE ADJUST oas e n sokat Bae A Bh eR eR ae BAR 2 4 222 DEPINE DELTAT lt e satsa be ewe Gog Be Sou eae ee wo 2 7 2 2 3 DEFINE EXECUTE AT END gt a sodot 0 000 c et eea 2 8 Peo DEFINE EXECUTE AT EXIT o toripe We Sh a i AT 2 10 2 2 5 DEFINE_EXECUTE_FROM_GUI 0 000 52 eee 2 11 Release 12 0 ANSYS Inc January 26 2009 l CONTENTS 2 3 2 2 6 DEFINE_EXECUTE_ON_LOADING o o co cox mia a og k nie a 05 PoE e 2 13 2 2 7 DEFINE EXECUTEAFTER CASE DATA se coco sered asados 2 16 ZAS DEFINE INIT lt i a ma ea a e ER ee o Aui pog i aie ek m 2 18 229 DEFINE ON DEMAND x pecset eon i Boe RM a eh aS A i 2 20 2210 DEFINE RW FILE gt g comio pe ace eB eee ee hk a a e 2 23 Model Specific DEFINE Macros ao
355. e P double yil double v 1 density double dvdt 0 0 int i for i 0 i lt n_specs i if yi i gt SMLL dvdt yili RKEOS_dvdt temp mw i density MIXTURE_mw yi i 8 84 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples return v temp dvdt eee c ttt T tT ooo E k k kkk Species Property Definitions Peete t ttt eet eT tC iT Tet eLeTCrCLererocrorecrcrorrorerorerrrererr rere e g void Mw molecular weight Kg Kgmol mw 0 18 01534 H20 mw 1 16 04303 CH4 mw 2 31 99880 02 mw 3 44 00995 C02 mw 4 28 01340 N2 void Pcrit critical pressure Pa pcrit 0 220 64e5 H20 pcrit 1 4 48e6 CH4 pcrit 2 5066250 02 perit 3 7 3834e6 C02 pcrit 4 33 98e5 N2 void Tcrit critical temperature K tcrit 0 647 H20 tcrit 1 191 CH4 tcrit 2 155 02 tcrit 3 304 CO2 tcrit 4 126 2 N2 void Vcrit critical specific volume m3 Kg verit 0 0 003111 H20 verit 1 0 006187 CH4 verit 2 0 002294 02 verit 3 0 002136 CO2 verit 4 0 003196 N2 Release 12 0 ANSYS Inc January 26 2009 8 85 Examples void NRK exponent n of function a T in Redlich Kwong equation of state int i for i 0 i lt n_specs i nrk i 0 4986 1 1735xomeg
356. e Pollut structure as the forward rate POLLUT_FRATE Pollut and reverse rate POLLUT_RRATE Pollut respectively i The data contained within the SO structure is specific only to the SO model Alternatively the Pollut structure contains data at each cell that is useful for all pollutant species e g forward and reverse rates gas phase temperature density The Pollut_Par structure contains auxil iary data common for all pollutant species e g equation solved universal gas constant species molecular weights Note that molecular weights ex tracted from the Pollut Par structure i e Pollut _Par gt sp IDX i mw for pollutant species NO HCN etc and Pollut _Par gt sp i mw for other species such as Oz has units of kg kg mol Example 1 The following compiled UDF named user_sox computes the rates for SO and SO3 formation according to the reaction given in Equation 2 3 10 Note that this UDF will replace the ANSYS FLUENT rate only if you select the Replace with UDF Rate option in the SOx Model dialog box Otherwise the rate computed in the UDF will be added to ANSYS FLUENT s default rate See Section 6 2 20 Hooking DEFINE_SOX_RATE UDF for details It is assumed that the release of fuel sulfur from fuel is proportional to the rate of release of volatiles and all sulfur is in the form of SO when released to the gas phase The reversible reaction for SO2 SO3 is given below with forward and reverse rates of reaction ky a
357. e Summing f n total_area Message Total Normal Force Before Summing f n total_force if RP_NODE Perform node synchronized actions here Does nothing in Serial total_area PRF_GRSUM1 total_area total_force PRF_GRSUM1 total_force endif RP_NODE endif RP_HOST Pass the node s total area and pressure to the Host for averaging node_to_host_real_2 total_area total_force Does nothing in SERIAL if RP_NODE SERIAL or HOST Message Total Area After Summing 7 f m2 n total_area Message Total Normal Force After Summing f N n total_force Message Average pressure on Surface d is f Pa n surface_thread_id total_force total_area endif RP_NODE 7 38 Release 12 0 ANSYS Inc January 26 2009 7 8 Parallel UDF Example The function begins by initializing the variables surface_thread_id total_area and total_force for all processes This is done because the variables are used by the serial host and node processes The compute nodes use the variables for computation purposes and the host uses them for message passing and displaying purposes Next the preprocessor is directed to compile thread face and area variables only on the serial and node versions and not the host since faces and threads are only defined in the serial and node versions of ANSYS FLUENT Note that in general the host will ignore these statements since its face and cell data
358. e UDS Diffusion Coefficients dialog box select a scalar equation e g uds 0 and select user defined anisotropic from the drop down list under Coefficient This will open the User Defined Functions dialog box Select the name of the UDF e g cyl_ortho_diff libudf you wish to hook and click OK The name of the UDF will be displayed in the text box below the Coefficient drop down list in the UDS Diffusion Coefficients dialog box Click OK and then click Change Create in the Create Edit Materials dialog box Note that you can hook a unique diffusion coefficient UDF for each scalar transport equation you have defined in your model See Section 2 7 2 DEFINE ANISOTROPIC DIFFUSIVITY for details about defining DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs and the User s Guide for general information about UDS anisotropic diffusivity 6 92 Release 12 0 ANSYS Inc January 26 2009 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs 6 6 2 Hooking DEFINE_UDS_FLUX UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_UDS_FLUX UDF the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the User Defined Scalars dialog box Figure 6 6 3 in ANSYS FLUENT Define User Defined Scalars User Defined Scalars Number of User Defined Scalars 2 a Inlet Diffusion User Defined Scalars O
359. e Weber number to determine the regime for i 0 i lt idim i if moving face_vel i WALL_F_VV f thread i WALL_F_GRID_VV f thread i else face_vel i 0 0 2 1 60 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros rel_vel i P_VEL p i face_vel i F vmag MAX NV_MAG rel_vel DPM_SMALL rel_dot_n MAX NV_DOT rel_vel normal DPM_SMALL weber_in P_RHO p SQR rel_dot_n P_DIAM p MAX DPM_SURFTEN p DPM_SMALL Regime where bouncing occurs We_in lt 80 Data from Mundo Sommerfeld and Tropea Int J of Multiphase Flow v21 2 pp151 173 1995 if weber_in lt 80 weber_out 0 6785 weber_in exp 0 04415 weber_in vnew rel_dot_n 1 0 sqrt weber_out MAX weber_in DPM_SMALL The normal component of the velocity is changed based on the experimental paper above i e the Weber number is based on the relative velocity for i 0 i lt idim i P_VEL p i rel_vel i vnew normal i face_vel i if weber_in gt 80 alpha acos rel_dot_n vmag Get one tangent vector by subtracting off the normal component from the impingement vector then cross the normal with the tangent to get an out of plane vector Release 12 0 ANSYS Inc January 26 2009 2 1 61 DEFINE Macros for i 0 i lt idim i tan_i i rel_vel i rel_dot_n normal i UNI
360. e compilation process is different for the two methods These differences are explained below Compiled UDFs Compiled UDFs are built in the same way that the ANSYS FLUENT executable itself is built A script called Makefile is used to invoke the system C compiler to build an object code library You initiate this action in the Compiled UDFs dialog box by clicking the Build button The object code library contains the native machine language translation of your higher level C source code The shared library must then loaded into ANSYS FLUENT at runtime by a process called dynamic loading You initiate this action in the Compiled UDFs dialog box by clicking the Load button The object libraries are specific to the computer architecture being used as well as to the particular version of the ANSYS FLUENT executable being run The libraries must therefore be rebuilt any time ANSYS FLUENT is upgraded when the computer s operating system level changes or when the job is run on a different type of computer In summary compiled UDFs are compiled from source files using the graphical user interface in a two step process The process involves the Compiled UDFs dialog box where you first build a shared library object file from a source file and then load the shared library that was just built into ANSYS FLUENT Interpreted UDFs Interpreted UDFs are interpreted from source files using the graphical user interface but in a single step process
361. e computer architecture being used during the ANSYS FLUENT session as well as to the particular version of the ANSYS FLUENT executable being run Therefore UDF object libraries must be rebuilt any time ANSYS FLUENT is upgraded when the computer s operating system level changes or when the job is run on a different type of computer architecture The generic process for compiling a UDF involves two steps compile build and load The compile build step takes one or more source files e g myudf c containing at least one UDF and compiles them into object files e g myudf o or myudf obj and then builds a shared library e g libudf with the object files If you compile your source file using the GUI this compile build process is executed when you click the Build button in the Compiled UDFs dialog box The shared library that you name e g libudf is automatically built for the architecture and version of ANSYS FLUENT you are running during that session e g hpux11 2d and will store the UDF object file s If you compile your source file using the TUI you will first need to setup target folders for the shared libraries modify a file named makefile to specify source parameters and then execute the Makefile which directs the compile build process Compiling a UDF using the TUI has the added advantage of allowing precompiled object files derived from non ANSYS FLUENT sources to be linked to ANSYS FLUENT Section 5 4 Link Precompiled
362. e information at a cell For example C_R c pt i can be used to return the density of the ith phase fluid at cell c The pointer pt i can also be retrieved using THREAD_SUB_THREAD discussed in Section 3 3 2 Phase Level Thread Pointer THREAD _SUB_THREAD using i as an argument The phase_domain_index can be retrieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details Mixture Domain Pointer DOMAIN_SUPER_DOMAIN You can use DOMAIN_SUPER_DOMAIN when your UDF has access to a particular phase level domain subdomain pointer and you want to retrieve the mixture level domain pointer DOMAIN SUPER DOMAIN has one argument subdomain Note that DOMAIN SUPER DOMAIN is similar in implementation to the THREAD_SUPER_THREAD macro described in Section 3 3 2 Mix ture Thread Pointer THREAD_SUPER_THREAD Domain subdomain Domain mixture_domain DOMAIN_SUPER_DOMAIN subdomain subdomain is a pointer to a phase level domain within the multiphase mixture It is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and the func tion is hooked to a primary or secondary phase in the mixture Note that in the cur rent version of ANSYS FLUENT DOMAIN_SUPER_DOMAIN will return the same pointer as Release 12 0 ANSYS Inc January 26 2009 3 67 Additional Macros for Writing UDFs Get_Domain 1
363. e inlet and extends to 0 0745 at the top and bottom of the inlet The source code can be interpreted or compiled in ANSYS FLUENT paaa o kkk kkk kkk kkk kk kkk kkk kk k kkk kkk kk kk kk kkk k k 4 4 k UDF for specifying steady state parabolic pressure profile boundary profile for a turbine vane KKK k ak ak ak ak aK K aK K K 2K 3K 3K 2K 3K 3K 3K 3K 3K 3K 3K A K K K 2K 3K 2K 3K 3K 3K 3K 3K 3K 2K 3K 2K 2K 2K 2K 2K kkk kk K KKK K include udf h DEFINE_PROFILE pressure_profile t i real x ND_ND this will hold the position vector real y face_t f begin_f_loop f t F_CENTROID x f t y x 1 F_PROFILE f t i 1 1e5 y y 0745 0745 0 1e5 end_f_loop f t The function named pressure_profile has two arguments t and i t is a pointer to the face s thread and i is an integer that is a numerical label for the variable being set within each loop 2 74 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Within the function body variable f is declared as a face A one dimensional array x and variable y are declared as real data types Following the variable declarations a looping macro is used to loop over each face in the zone to create a profile or an array of data Within each loop F_CENTROID returns the value of the face centroid array x for the face with index f that is on the thread pointed to by t The y coordinate stored in x 1 is assigned to variable y and is then
364. e partitioned all of the domains and threads in a mesh are mirrored on each compute node Figure 7 1 3 The threads are stored as linked lists as in the serial solver The compute nodes can be implemented on a massively parallel computer a multiple CPU workstation or a network of workstations using the same or different operating systems Release 12 0 ANSYS Inc January 26 2009 7 3 Parallel Considerations 7 1 1 Command Transfer and Communication The processes that are involved in an ANSYS FLUENT session running in parallel are defined by Cortex a host process and a set of n compute node processes referred to as compute nodes with compute nodes being labeled from 0 to n 1 Figure 7 1 4 The host receives commands from Cortex and passes commands to compute node 0 Compute node 0 in turn sends commands to the other compute nodes All compute nodes except 0 receive commands from compute node 0 Before the compute nodes pass messages to the host via compute node 0 they synchronize with each other Figure 7 1 4 shows the relationship of processes in parallel ANSYS FLUENT Each compute node is virtually connected to every other compute node and relies on its communicator to perform such functions as sending and receiving arrays synchro nizing performing global reductions such as summations over all cells and establishing machine connectivity An ANSYS FLUENT communicator is a message passing library For example
365. e t_relax const real t_relax 0 001 seconds get the cell and Thread that the particle is currently in cell tc P_CELL tp Thread t P_CELL_THREAD tp Particle index for looping over all particles in the cell Particle pi loop over all particles in the cell to find their mass weighted mean velocity and diameter int i real u_mean 3 0 mass_mean 0 real d_orig P_DIAM tp real decay 1 exp t_relax begin_particle_cell_loop pi c t mass_mean P_MASS pi for i 0 1 lt 3 i u_mean i P_VEL pi i P_MASS pi end_particle_cell_loop pi c t relax particle velocity to the mean and diameter to the Release 12 0 ANSYS Inc January 26 2009 2 1 95 DEFINE Macros initial diameter over the relaxation time scale t_relax if mass_mean gt 0 for i 0 i lt 3 i u_mean i mass_mean for i 0 i lt 3 i P_VEL tp i decay u_mean i P_VEL tp i P_DIAM tp decay P_INIT_DIAM tp P_DIAM tp adjust the number in the droplet parcel to conserve mass P_N tp CUB d_orig P_DIAM tp Hooking a DPM Spray Collide UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_SPRAY_COLLIDE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model
366. ead that contains partition boundary faces For example if your UDF is tasked with summing data over all of the faces in a mesh then as each node loops over its faces duplicated partition boundary faces can be counted twice For this reason one compute node in every adjacent set is assigned by ANSYS FLUENT as the principal compute node with respect to partition boundary faces In other words although each face can appear on one or two partitions it can only officially belong to one of them The boolean macro PRINCIPAL_FACE_P f t returns TRUE if the face f is a principal face on the current compute node 7 8 Release 12 0 ANSYS Inc January 26 2009 7 3 Parallelizing Your Serial UDF PRINCIPAL _FACE_P You can use PRINCIPAL_FACE_P to test whether a given face is the principal face before including it in a face loop summation In the sample source code below the area of a face is added to the total area only if it is the principal face Note that PRINCIPAL_FACE_P is always TRUE for the serial version i PRINCIPAL_FACE_P can be used only in compiled UDFs Example begin_f_loop f t if PRINCIPAL_FACE_P f t tests if the face is the principle face FOR COMPILED UDFs ONLY F_AREA area f t computes area of each face total_area NV_MAG area computes total face area by accumulating magnitude of each face s area end_f_loop f t Exterior Thread Storage Each thread stores the data associa
367. eady manner include udf h pE aaao ooo ooo o A A A I K KK aK aK AK I A A A 4 kk kkk UDF that samples discrete phase size and velocity distributions within the domain POR CAAA AGAR RI I OIA CA A A A 1 21 1 21 21 k kkk 4 24 24 24 kkk define REMOVE_PARTICLES FALSE DEF INE_DPM_OUTPUT discrete_phase_sample header fp p t plane if RP_2D real y if header par_fprintf_head fp Time s R m X velocityl m s par_fprintf_head fp W velocity m s R velocity m s par_fprintf_head fp Drop Diameter m Number of Drops ap par_fprintf_head fp Temperature K Initial Diam m par_fprintf_head fp Injection Time s n if NULLP p return 2 1 84 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros if rp_axi amp amp sg_swirl rp_ke y MAX sqrt SQR P_POS p 1 SQR P_POS p 2 DPM_SMALL else y P_POS p 1 par_fprintf fp d 4d fe Wf Wf Pf EF he he EF he FE n P_INJ_ID P_INJECTION p p gt part_id P_TIME p y P_VEL p 0 P_VEL p 1 P_VEL p 2 P_DIAM p P_N p P_T p P_INIT_DIAM p p gt time_of_birth else real r xX y if header par_fprintf_head fp Time s R m x velocity m s par_fprintf_head fp y velocity m s z velocity m s ws par_fprintf_head fp Drop Diameter m Number of Drops par_fprintf_head fp Temperature K Initial Diam m ne par_fprintf_head fp Injec
368. eat Flux Chemistry Step Aamann v Mixing Model Constant Cphi Figure 6 2 1 The User Defined Function Hooks Dialog Box Select the function name e g user_chem_step libudf in the Chemistry Step drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 1 DEFINE_CHEM_STEP for details about defining DEFINE_CHEM_STEP func tions 6 14 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 2 Hooking DEFINE_CPHI UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_CPHI UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 2 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 2 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Chemistry Step none Mixing Model Constant Cphi aparraren FA Figure 6 2 2 The User Defined Function Hooks Dialog Box EDC or PDF Transport models must be enabled to hook the mixing model constant Cphi UDFs Select the function name e g
369. econdary phase s phase dependent primary and secondary phases s primary and secondary phases s primary and secondary phases s mixture mixture Release 12 0 ANSYS Inc January 26 2009 C 13 Quick Reference Guide for Multiphase DEFINE Macros Table C 6 2 DEFINE Macro Usage for the Eulerian Model Per Phase Tur bulence Flow Variable Macro Phase Specified On Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source user defined scalar source velocity temperature turbulence kinetic energy turbulence dissipation rate granular flux granular temperature porosity viscous resistance inertial resistance user defined scalar DEF INE_SOURCE DEF INE_SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s mixture primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s primary and secondary phase s mixture
370. ed Enable the Display Assembly Listing option if you want a listing of assembly language code to appear in your console when the function interprets This option will be saved in your case file so that when you read the case in a subsequent ANSYS FLUENT session the assembly code will be automatically displayed Release 12 0 ANSYS Inc January 26 2009 8 7 Examples 6 Click Interpret to interpret your UDF If the Display Assembly Listing option was enabled then the assembly code will appear in the console when the UDF is inter preted as shown below inlet_x_velocity local pointer thread r0 local int position r1 local end save local int x r3 begin data 8 bytes 0 bytes initialized local float y r4 push float 0 local float h r5 pre inc int f r6 pop int b L3 28 restore restore ret v Note that if your compilation is unsuccessful then ANSYS FLUENT will report an error and you will need to debug your program See Sec tion 4 3 Common Errors Made While Interpreting A Source File for details 7 Click Close when the interpreter has finished 8 Write the case file The interpreted UDF will be saved with the case file so that the function will be automatically interpreted whenever the case is subsequently read 8 8 Release 12 0 ANSYS Inc January 26 2009 8 1 Step By Step UDF Example Compile the Source File You can compile your UDF using the text user interface TUI or the
371. ed and the build files will be stored in the shared library you specified e g libudf As the compile build process begins a Warning dialog box Figure 5 2 4 will appear reminding you that the source file s need to be in the same folder as the case and data files Click OK to close the dialog and continue with the build Warning A Make sure that UDF source files are in the directory that contains your case and data files Cancel Figure 5 2 4 The Warning Dialog Box As the build process progresses the results of the build will be displayed on the console You can also view the compilation history in the log file that is saved in your working folder Console messages for a successful compile build for a source file named udfexample c and a UDF library named libudf for a Windows architecture are shown below Deleted old libudf ntx86 2d libudf d1l 1 file s copied system copy C Program Files ANSYS Inc v1i20 fluent fluent12 0 9 src makefile_nt udf libudf ntx86 2d makefile 1 file s copied chdir libudf chdir ntx86 2d udfexample c Generating udf_names c because of makefile udfexample obj udf_names c Linking libudf dll because of makefile user_nt udf udf_names obj udfexample obj Release 12 0 ANSYS Inc January 26 2009 5 2 Compiling a UDF Using the GUI Microsoft R Incremental Linker Version 7 10 3077 Copyright C Microsoft Corporation All rights reserved Creating library libudf 1l
372. ed in the UDF will be added to ANSYS FLUENT s default rate See Section 6 2 12 Hooking DEFINE_NOX_RATE UDF for details See Section 3 2 7 NO Macros for details about the NO macros e g POLLUT_EQN MOLECON ARRH that are used in pollutant rate calculations in this UDF paaa aaao ooo ooo o kkk kk kk kkk kkk kk UDF example of User Defined NOx Rate for ANSYS FLUENT 12 or later If used with the Replace with UDF radio buttons activated this UDF will exactly reproduce the default ANSYS FLUENT NOx rates for prompt NOx pathway The flag Pollut_Par gt pollut_io_pdf IN_PDF should always be used for rates other than that from char N so that if requested the contributions will be PDF integrated Any contribution from char must be included within a switch statement of the form Pollut_Par gt pollut_io_pdf OUT_PDF Arguments char nox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the NOx rate is to be applied Pollut_Cell Pollut Pointer to Pollut structure Pollut_Parameter Pollut_Par Pointer to Pollut_Par structure NOx_Parameter NOx Pointer to NOx structure BR RR a a a 3k 2k 2 a 2k 2k 3k 2k 2k a ok 2k 2k ok 2k 2k 2 ak 2k 2k 2 ak ak include udf h DEFINE_NOX_RATE user_nox c t Pollut Pollut_Par NOx NOx gt prompt_nox Flag to indicate Prompt NOx is enabled NOx gt prompt_udf_replace Flag to indicate UDF replace Pollut_Pa
373. ed print to a file fscanf fp format formatted read from a file Fa It is not possible to use the scanf C function in ANSYS FLUENT fopen FILE fopen char filename char mode The function fopen opens a file in the mode that you specify It takes two arguments filename and mode filename is a pointer to the file you want to open mode is the mode in which you want the file opened The options for mode are read r write w and append a Both arguments must be enclosed in quotes The function returns a pointer to the file that is to be opened Before using fopen you will first need to define a local pointer of type FILE that is defined in stdio h e g fp Then you can open the file using fopen and assign it to the local pointer as shown below Recall that stdio h is included in the udf h file so you don t have to include it in your function FILE fp define a local pointer fp of type FILE fp fopen data txt r open a file named data txt in read only mode and assign it to fp A 14 Release 12 0 ANSYS Inc January 26 2009 A 13 C Library Functions fclose int fclose FILE fp The function fclose closes a file that is pointed to by the local pointer passed as an argument e g fp fclose fp close the file pointed to by fp printf int printf char format The function printf is a general purpose printing function that prints to the console in a format that you s
374. ed to define a function called where_am_i This function queries to determine which type of process is executing and then displays a message on that computed node s mon itor Release 12 0 ANSYS Inc January 26 2009 7 13 Parallel Considerations Example DOCG OCA AOA OIA CCA A ACA AK Simple UDF that uses compiler directives FEOF OIA IAAI RI A a kk ka include udf h DEFINE_ADJUST where_am_i domain if RP_HOST Message I am in the host process n endif RP_HOST if RP_NODE Message I am in the node process with ID d n myid myid is a global variable which is set to the multiport ID for each node Hendif RP_NODE if PARALLEL Message I am in the serial process n endif PARALLEL This simple allocation of functionality between the different types of processes is useful in a limited number of practical situations For example you may want to display a message on the compute nodes when a particular computation is being run by using RP_NODE or RP_HOST Or you can also choose to designate the host process to display messages by using RP_HOST or RP_NODE Usually you want messages written only once by the host process and the serial process Simple messages such as Running the Adjust Function are straightforward Alternatively you may want to collect data from all the nodes and print the total once from the host To perform this type of operation your UDF will need some
375. edefined macros and functions supplied by ANSYS FLUENT to access AN SYS FLUENT solver data and perform other tasks Chapter 3 Additional Macros for Writing UDFs e are executed as interpreted or compiled functions Chapter 4 Interpreting UDFs and Chapter 5 Compiling UDFs e are hooked to an ANSYS FLUENT solver using a graphical user interface dialog box Chapter 6 Hooking UDFs to ANSYS FLUENT e use and return values specified in SI units 1 2 Release 12 0 ANSYS Inc January 26 2009 1 2 Why Use UDFs 1 2 Why Use UDFs UDFs allow you to customize ANSYS FLUENT to fit your particular modeling needs UDFs can be used for a variety of applications Some examples include e customization of boundary conditions material property definitions surface and volume reaction rates source terms in ANSYS FLUENT transport equations source terms in user defined scalar UDS transport equations diffusivity functions etc e adjustment of computed values on a once per iteration basis e initialization of a solution e asynchronous on demand execution of a UDF e execution at the end of an iteration upon exit from ANSYS FLUENT or upon loading of a compiled UDF library e postprocessing enhancement e enhancement of existing ANSYS FLUENT models e g discrete phase model mul tiphase mixture model discrete ordinates radiation model Simple examples of UDFs that demonstrate usage are provided with most DEFINE macro description
376. eeded but only a mixture pointer is passed Get_Domain domain_id domain_id is an integer whose value is 1 for the mixture domain but the values for the phase domains can be any integer greater than 1 The ID for a particular phase can be found be selecting it in the Phases task page in ANSYS FLUENT Single Phase Flows In the case of single phase flows domain_id is 1 and Get_Domain 1 will return the fluid domain pointer DEF INE_ON_DEMAND my_udf Domain domain domain is declared as a variable domain Get_Domain 1 returns fluid domain pointer Release 12 0 ANSYS Inc January 26 2009 3 31 Additional Macros for Writing UDFs Multiphase Flows In the case of multiphase flows the value returned by Get_Domain is either the mixture level a phase level or an interaction phase level domain pointer The value of domain_id is always 1 for the mixture domain You can obtain the domain id using the ANSYS FLUENT graphical user interface much in the same way that you can determine the zone ID from the Boundary Conditions task page Simply go to the Phases task page in ANSYS FLUENT and select the desired phase The domain_id will then be displayed You will need to hard code this integer ID as an argument to the macro as shown below DEF INE_ON_DEMAND my_udf Domain mixture_domain mixture_domain Get_Domain 1 returns mixture domain pointer and assigns to variable Domain subdomain
377. eger that starts with O for the primary phase and is incremented by one for each secondary phase phase_domain_index is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a phase domain index argument DEFINE_EXCHANGE_ PROPERTY DEFINE_VECTOR_EXCHANGE_ PROPERTY and your UDF is hooked to a specific interaction phase Otherwise you will need to hard code the in teger value of phase domain index to the DOMAIN SUB DOMAIN macro If your multi phase model has only two phases defined then phase _domain_index is 0 for the primary phase and 1 for the secondary phase However if you have more than one secondary phase defined for your multiphase model you will need to use the PHASE_DOMAIN_INDEX utility to retrieve the corresponding phase_domain_index for the given domain See Section 3 3 2 Phase Domain Index PHASE _DOMAIN_INDEX for details Release 12 0 ANSYS Inc January 26 2009 3 65 Additional Macros for Writing UDFs Phase Level Thread Pointer THREAD_SUB_THREAD The THREAD_SUB_THREAD macro can be used to retrieve the phase level thread sub thread pointer given the phase domain index THREAD_SUB_THREAD has two arguments mixture_thread and phase_domain_index The function returns the phase level thread pointer for the given phase domain index Note that THREAD SUB THREAD is similar in implementation to the DOMAIN_SUB_DOMAIN macro described in Section 3 3 2 Phase Do main Pointer DOM
378. el sne sm 66 bee eee bowed e55 Bees C2 Mestre Model aa s 244 64 2 D446 464 REGS EK ES C 3 Eulerian Model Laminar Flow lt 2 54 46 bau C 4 Eulerian Model Mixture Turbulence Flow C 5 Eulerian Model Dispersed Turbulence Flow C 6 Eulerian Model Per Phase Turbulence Flow Release 12 0 ANSYS Inc January 26 2009 xi CONTENTS XII Release 12 0 ANSYS Inc January 26 2009 About This Document User defined functions UDFs allow you to customize ANSYS FLUENT and can signifi cantly enhance its capabilities This UDF Manual presents detailed information on how to write compile and use UDFs in ANSYS FLUENT Examples have also been included where available General information about C programming basics is included in an appendix Information in this manual is presented in the following chapters e Chapter 1 Overview e Chapter 2 DEFINE Macros e Chapter 3 Additional Macros for Writing UDFs e Chapter 4 Interpreting UDFs e Chapter 5 Compiling UDFs e Chapter 6 Hooking UDFs to ANSYS FLUENT e Chapter 7 Parallel Considerations e Chapter 8 Examples This document provides some basic information about the C programming language Appendix A as it relates to user defined functions in ANSYS FLUENT and assumes that you are an experienced programmer in C If you are unfamiliar with C please consult a C language reference guide e g 6 9 before you begin the process of writin
379. elease 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros where c is the mean reaction progress variable p is the density and U is the turbulent flame speed In the UDF example the turbulent flame speed is modeled as U Ui4 1 u U 2 3 12 where U is the laminar flame speed and u is the turbulent fluctuation Note that the partially premixed combustion model is assumed to be enabled see Chapter 18 Modeling Partially Premixed Combustion in the separate User s Guide so that the unburned density and laminar flame speed are available as polynomials See Chapter 3 Additional Macros for Writing UDFs for details on the NULLP THREAD_STORAGE and SV_VARS macros pE aaao oo oo o o CICA A A A KKK KK k CA A A A A kk k kkk UDF that specifies a custom turbulent flame speed and source for the premixed combustion model BEA AAR I ACOA I A A I I KKK aK AK A kkk kk kkk kkk include udf h include sg_pdf h not included in udf h so must include here DEFINE_TURB_PREMIX_SOURCE turb_flame_src c t turb_flame_speed source real up TRB_VEL_SCAL c t real ut ul grad_c rho_u Xl DV ND_ND ul C_LAM_FLAME_SPEED c t Calculate_unburnt_rho_and_X1 t amp rho_u amp X1 if NNULLP THREAD_STORAGE t SV_PREMIXC_G NV_V DV C_STORAGE_R_NV c t SV_PREMIXC_G grad_c sqrt NV_DOT DV DV ut ul sqrt 1 SQR up ul turb_flame_speed ut source rho_ux ut grad_c
380. ell looping macros you can use to loop over interior cells only exterior cells only or both interior and exterior cells Interior Cell Looping Macro The macro begin end_c_loop_int loops over interior cells in a partitioned mesh Fig ure 7 5 1 and is identified by the suffix int This macro pair can also be used by the serial version of ANSYS FLUENT to loop over all cells in the given thread It contains a begin and end statement and between these statements operations can be performed on each of the thread s interior cells in turn The macro is passed a cell index c and a cell thread pointer tc begin_c_loop_int c tc end_c_loop_int c tc 7 22 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Figure 7 5 1 Looping Over Interior Cells in a Partitioned Mesh Using begin end_c_loop_int indicated by the green cells Example real total_volume 0 0 begin_c_loop_int c tc C_VOLUME gets the cell volume and accumulates it The end result will be the total volume of each compute node s respective mesh total_volume C_VOLUME c tc end_c_loop_int c tc Exterior Cell Looping Macro The macro begin end_c_loop_ext loops over exterior cells in a partitioned mesh Fig ure 7 5 2 and is identified by the suffix ext It contains a begin and end statement and between these statements operations can be performed on each of the thread s exterior cells in turn The macro is passe
381. emp temp cp 1 i temp 0 5 cp 2 i temp 0 333333 cp 3 i 0 25 cp 4 i temp cp_int_ref i if cp_integral lt SMLL cp_integral 1 0 v 1 density vO rgas i temp ref_p dadt nrk i afun temp delta_s rgas i log v bb i v0 dadt b0 i log v b0 Li v return S_REF cp_integraltdelta_s J Kg K FUNCTION RKEOS_viscosity double RKEOS_viscosity double temp int i double mu tr tc pcatm tr temp tcrit i tc terit la peatm pcritli 101325 mu 6 3e 7 sqrt mw i pow pcatm 0 6666 pow tc 0 16666 pow tr 1 5 tr 0 8 return mu FUNCTION RKEOS_thermal_conductivity 8 92 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double RKEOS_thermal_conductivity double temp int i double cp mu cp RKEOS_Cp_ideal_gas temp i mu RKEOS_viscosity temp i return cp 1 25 rgas i mu DOR OOOO k k RK I k kkk kkk k kkk kkk Mixture Functions Structure DORCAS AI II I o I aK 5 4 kkk kk UDF_EXPORT RGAS_Functions RealGasFunctionList MIXTURE_Setup initialize MIXTURE_density density MIXTURE_enthalpy sensible enthalpy MIXTURE_entropy entropy MIXTURE_specific_heat specific_hea
382. eneous reaction rate DEF INE_VECTOR_ EXCHANGE PROPERTY DEFINE EXCHANGE DEF INE_MASS_TRANSFER DEF INE_HET_RXN_RATE phase interaction phase interaction phase interaction phase interaction C 3 Eulerian Model Laminar Flow Tables C 3 1 C 3 3 list the variables that can be customized using UDFs for the laminar flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable Release 12 0 ANSYS Inc January 26 2009 Quick Reference Guide for Multiphase DEFINE Macros Table C 3 1 DEFINE Macro Usage for the Eulerian Model Laminar Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux flow direction components velocity magnitude temperature pressure user defined scalar boundary value discrete phase boundary value DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE_DPM_BC secondary phase s phase dependent primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s mixture mixture mixture Fluid mass source momentum source energy source species source granular temperature source user defined scalar source velocity temperature DEFINE
383. enter real swirl_center 2 212 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros real piston_displacement lambda CA l r if RP_NODE 1 RP_Get_List_Ref_Float dynamesh in cyn piston data 0 r 0 5 RP_Get_List_Ref_Float dynamesh in cyn piston data 1 endif host_to_node_real_2 l r lambda r 1 CA CURRENT_TIME RPM 6 0 RP_Get_Real dynamesh in cyn crank start angle M_PI 180 piston_displacement r 1 1 lambda cos CA pow 1 lambda lambda sin CA sin CA 0 5 lambda swirl_center 0 0 swirl_center 1 0 if Zmin_at_TDC lt Zmax swirl_center 2 0 5 Zmin_at_TDC Zmax piston_displacement else swirl_center 2 0 5 Zmin_at_TDC Zmax piston_displacement return DEFINE_DYNAMIC_ZONE_PROPERTY swirl_udf dt sc my_swirl_center sc Hooking a Swirl Center UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DYNAMIC_ZONE_PROPERTY is compiled as described in Chapter 5 Compiling UDFs the name of the argument that you sup plied as the first DEFINE macro argument will become visible in the In Cylinder Output Controls dialog box in ANSYS FLUENT See Section 6 5 2 Hooking DEFINE DYNAMIC ZONE PROPERTY UDFs for details on how to hook your DEFINE_DYNAMIC_ZONE_PROPERTY UDF to ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 2 213 DEFINE Macros Variable Cell Layering Height You can use DEFINE_DYNAMIC_ZONE_PROPE
384. er the call to DEFINE_HEAT_FLUX so the total heat flux at the wall will be the currently computed heat flux based on the activated models with any modifications as defined by your UDF The diffusive heat flux qid and radiative heat flux qir are computed by ANSYS FLUENT according to the following equations qid qir cid 0 cid 1 C_T c0 t0 cid 2 F_T f t cid 3 pow F_T f t 4 cir 0 cir 1 C_T c0O t0 cir 2 F_T f t cir 3 pow F_T f t 4 The sum of gid and qir defines the total heat flux from the fluid to the wall this direction being positive flux and from an energy balance at the wall equals the heat flux of the surroundings exterior to the domain Note that heat flux UDFs defined using DEFINE_HEAT_FLUX are called by ANSYS FLUENT from within a loop over wall faces i In order for the solver to compute C_T and F_T the values you supply to cid 1 and cid 2 should never be zero Example Section 8 2 5 Implementing ANSYS FLUENT s P 1 Radiation Model Using User Defined Scalars provides an example of the P 1 radiation model implementation through a user defined scalar An example of the usage of the DEFINE_HEAT_FLUX macro is included in that implementation Hooking a Heat Flux UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_HEAT_FLUX is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first D
385. es BOA ooo oo oo kkk kkk kkk kkk 2k 2k include udf h DEFINE_UDS_UNSTEADY my_uds_unsteady c t i apu su real physical_dt vol rho phi_old physical_dt RP_Get_Real physical time step vol C_VOLUME c t Release 12 0 ANSYS Inc January 26 2009 2 235 DEFINE Macros rho C_R_M1 c t xapu rho vol physical_dt implicit part phi_old C_STORAGE_R c t SV_UDSI_M1 i su rhoxvol phi_old physical_dt explicit part Hooking a UDS Unsteady Function to ANSYS FLUENT After the UDF that you have defined using DEFINE UDS UNSTEADY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my_uds_unsteady will become visible and selectable in the User Defined Scalars dialog box in ANSYS FLU ENT See Section 6 6 3 Hooking DEFINE_UDS_UNSTEADY UDFs for details 2 236 Release 12 0 ANSYS Inc January 26 2009 Chapter 3 Additional Macros for Writing UDFs 3 1 This chapter provides predefined macros that you can use when defining your user defined function UDF e Section 3 1 Introduction e Section 3 2 Data Access Macros e Section 3 3 Looping Macros e Section 3 4 Vector and Dimension Macros e Section 3 5 Time Dependent Macros e Section 3 6 Scheme Macros e Section 3 7 Input Output Macros e Section 3 8 Miscellaneous Macros Introduction ANSYS FLUENT provides numerous
386. es this by splitting up the computational domain into mul tiple partitions Figure 7 1 1 and assigning each data partition to a different compute process referred to as a compute node Figure 7 1 2 Each compute node executes the same program on its own data set simultaneously with every other compute node The host process or simply the host does not contain mesh cells faces or nodes except when using the DPM shared memory model Its primary purpose is to interpret commands from Cortex the ANSYS FLUENT process responsible for user interface and graphics related functions and in turn to pass those commands and data to a compute node which distributes it to the other compute nodes Release 12 0 ANSYS Inc January 26 2009 7 1 Parallel Considerations Figure 7 1 1 Partitioned Mesh in Parallel ANSYS FLUENT Figure 7 1 2 Partitioned Mesh Distributed Between Two Compute Nodes 7 2 Release 12 0 ANSYS Inc January 26 2009 7 1 Overview of Parallel ANSYS FLUENT Cell Threads Compute Node 0 Face Threads Cell Threads Compute Node 1 Face Threads Figure 7 1 3 Domain and Thread Mirroring in a Distributed Mesh Compute nodes store and perform computations on their portion of the mesh while a single layer of overlapping cells along partition boundaries provides communication and continuity across the partition boundaries Figure 7 1 2 Even though the cells and faces ar
387. esistance DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE secondary phase s primary and secondary phase s mixture primary and secondary phase s primary and secondary phase s user defined scalar DEFINE_PROFILE mixture Wall species mass fraction DEFINE PROFILE mixture shear stress components moving velocity components heat flux temperature heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature granular flux granular temperature user defined scalar boundary value discrete phase boundary value DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_DPM_BC primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity conductivity granular solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE TURBULENT VISCOSITY secondary phase s secondary phase s secondary ph
388. ess afun press alt rgas press a2t alt bO dadt press a3t dadt bb press return a3t v a2t v ait a2t tv 2 a1t 3 v FUNCTION RKEOS_Cp_ideal_gas Returns ideal gas specific heat given T 7 7 7 eee double RKEOS_Cp_ideal_gas double temp return CC1 temp CC2 temp CC3 temp CC4 temp CC5 FUNCTION RKEOS_H_ideal_gas Returns ideal gas specific enthalpy given T n ne double RKEOS_H_ideal_gas double temp return temp CC1 temp 0 5 CC2 temp 0 333333 CC3 temp 0 25 CC4 temp 0 2 CC5 8 60 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples FUNCTION RKEOS_specific_heat Returns specific heat given T and rho double RKEOS_specific_heat double temp double density double P double yi double delta_Cp press v dvdt dadt double afun a0 pow TCRIT temp NRK press RKEOS_pressure temp density v 1 density dvdt RKEOS_dvdt temp density dadt NRK afun temp delta_Cp press dvdt rgas dadt 1 NRK b0 log v b0 v afun 1 NRK dvdt v v b0 return RKEOS_Cp_ideal_gas temp tdelta_Cp J Kg K
389. ess them with the F_PART macro There is rarely a need for face partition IDs in parallel UDFs 7 5 7 Message Displaying Macros You can direct ANSYS FLUENT to display messages on a host node or serial process using the Message utility To do this simply use a conditional if statement and the appropriate compiler directive e g if RP_NODE to select the process es you want the message to come from This is demonstrated in the following example Example if RP_NODE Message Total Area Before Summing f n total _area endif RP_NODE In this example the message will be sent by the compute nodes It will not be sent by the host or serial process Message0 is a specialized form of the Message utility Message0 will send messages from compute node 0 only and is ignored on the other compute nodes without having to use a compiler directive Note that MessageO will also display messages on a serial process Example Let Compute Node O display messages Message0 Total volume f n total_volume 7 28 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs 7 5 8 Message Passing Macros High level communication macros of the form node_to_host and host_to_node that are described in Section 7 5 2 Communicating Between the Host and Node Processes are typically used when you want to send data from the host to all of the compute nodes or from node 0 to the host You cannot however use
390. essing for example or by other UDFs i Note that F_UDMI is available for wall and flow boundary faces only Table 3 2 37 Storage of User Defined Memory on Faces mem h Macro Argument Types Usage F_UDMI f t i face_t f Thread t int i stores the face value of a user defined memory with index i There are three arguments to F_UDMI f t and i f is the face identifier t is a pointer to the face thread and i is an integer index that identifies the memory location where data is to be stored An index i of 0 corresponds to user defined memory location 0 or User Memory 0 Example Compute face temperature and store in user defined memory begin_f_loop f t temp F_T f t F_UDMI f t 0 temp tmin tmax tmin end_f_loop f t See Section 2 5 4 DEFINE DPM EROSION for another example of F_UDMI usage 3 48 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros C_UDMI You can use C_UDMI to access or store the value of the user defined memory in a cell C_UDMI can be used to allocate up to 500 memory locations in order to store and retrieve the values of cell field variables computed by UDFs Table 3 2 38 These stored values can then be used for postprocessing for example or by other UDFs See Section 3 2 9 Ex ample UDF that Utilizes UDM and UDS Variables for an example of C_UDMI usage Table 3 2 38 Storage of User Defined Memory in Cells mem h Macro
391. etails F PROFILE is typically used along with DEFINE PROFILE and is a predefined macro sup plied by ANSYS FLUENT F_PROFILE stores a boundary condition in memory for a given face and thread and is nested within the face loop as shown in the examples below It is important to note that the index i that is an argument to DEFINE_PROFILE is the same argument to F_PROFILE F_PROFILE uses the thread pointer t face identifier f and index i to set the appropriate boundary face value in memory See Section 3 2 6 Set Boundary Condition Value F_PROFILE for a description of F_PROFILE Note that in the case of porosity profiles you can also utilize C_PROFILE to define those types of functions See Release 12 0 ANSYS Inc January 26 2009 2 73 DEFINE Macros the example UDFs provided below In multiphase cases a DEFINE_PROFILE UDF may be called more than once particularly if the profile is used in a mixture domain thread If this needs to be avoided then add the prefix MP_ to the UDF name The function will then be called only once even if it is used for more than one profile Example 1 Pressure Profile The following UDF named pressure_profile generates a parabolic pressure profile according to the equation 2 siox Orxi 2 Pty X 0 0745 Note that this UDF assumes that the mesh is generated such that the origin is at the geometric center of the boundary zone to which the UDF is to be applied y is 0 0 at the center of th
392. eting UDFs AL AMO sassis ole ok we ee ES RE EES AT Location ofthe ud h File lt lt 20020 soep 4d eee See eS ae Limitations s e ok we eee eee Ee A eee eee Go 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box 4 3 Common Errors Made While Interpreting A Source File 5 Compiling UDFs gl AiR e sesa ae ewe Rede SEHR ES EEE RE EER SLI Locationoftheundf h File lt e a ase eh Hehe ee ye Giles Compiles 22205 6 obeyed Gee oe ee Ee eee ew oe eS 5 2 Compilne a UDF Using the GUI lt e cba ck nee tempa teirt Release 12 0 ANSYS Inc January 26 2009 4 1 4 1 4 2 4 2 4 3 4 5 CONTENTS vi 23 Complea UDF Using tie TUL veerra a eae eee Se eee ee eS 5 3 1 Set Up the Directory Siruciire cs ss sora sses as ar 5 3 2 Build the UDF Library o ss ss cacc be Cae esasi gaa 533 L adtihe UDF Library sos sorsak k Oe eee SERS 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources 5 4 1 Example Link Precompiled Objects to ANSYS FLUENT 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box 5 6 Common Errors When Building and Loading a UDF Library 5 7 Special Considerations for Parallel ANSYS FLUENT Hooking UDFs to ANSYS FLUENT 6 1 Hooking General Purpose UDFs a naaa 2 ee eee ee HR eS 6 1 1 Hooking DEFINE_ADJUST UDVs e 2 4444 44444 4 amp es oo G12 Hoolange DEFINE DELTAT UDFSs 4 lt 444 464464442 8 6 1 3 Hooking DEFINE_EXECUTE_ATEND UDF
393. etween float for single precision arithmetic and double for double precision arithmetic Since the interpreter makes this assignment automatically it is good programming practice to use the real typedef when declaring all float and double data type variables in your UDF A 2 Release 12 0 ANSYS Inc January 26 2009 A 4 Constants A 4 Constants Constants are absolute values that are used in expressions and need to be defined in your C program using define Simple constants are decimal integers e g 0 1 2 Constants that contain decimal points or the letter e are taken as floating point constants As a convention constants are typically declared using all capitals For example you may set the ID of a zone or define constants YMIN and YMAX as shown below define WALL_ID 5 define YMIN 0 0 define YMAX 0 4064 A 5 Variables A variable or object is a place in memory where you can store a value Every variable has a type e g real a name and a value and may have a storage class identifier static or extern All variables must be declared before they can be used By declaring a variable ahead of time the C compiler knows what kind of storage to allocate for the value Global variables are variables that are defined outside of any single function and are visible to all function s within a UDF source file Global variables can also be used by other functions outside of the source file unless they are declared as stati
394. f t n node F_NODE f t n Release 12 0 ANSYS Inc January 26 2009 3 59 Additional Macros for Writing UDFs Here n is the local node index number The index number can be used with the F_NODE macro to obtain the global face node number e g node F_NODE f t n See Section 2 6 4 DEFINE_GRID_MOTION for an example of a UDF that uses f_node_loop 3 3 1 Multiphase Looping Macros This section contains a description of looping macros that are to be used for multiphase UDFs only They enable your function to loop over all cells and faces for given threads or domains Refer to Section 1 10 1 Multiphase specific Data Types and in particular Figure 1 10 1 for a discussion on hierarchy of structures within ANSYS FLUENT Looping Over Phase Domains in Mixture sub_domain_loop The sub_domain_loop macro loops over all phase domains subdomains within the mix ture domain The macro steps through and provides each phase domain pointer defined in the mixture domain as well as the corresponding phase domain index As discussed in Section 1 10 1 Multiphase specific Data Types the domain pointer is needed in part to gain access to data within each phase Note that sub_domain_loop is similar in im plementation to the sub_thread_loop macro described below int phase_domain_index index of subdomain pointers Domain mixture_domain Domain subdomain sub_domain_loop subdomain mixture_domain phase_domain_index The
395. f the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model dialog box in ANSYS FLUENT See Section 6 4 2 Hooking DEFINE_DPM_BODY_FORCE UDFs for details on how to hook your DEFINE_DPM_BODY_FORCE UDF to ANSYS FLUENT 2 5 3 DEFINE DPM DRAG Description You can use DEFINE_DPM_DRAG to specify the drag coefficient Cp between particles and fluid defined by the following equation 18u CpRe Fp J PpD 24 Usage DEFINE DPM DRAG name Re p Argument Type Description symbol name UDF name real Re particle Reynolds number based on the particle diameter and relative gas velocity Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Function returns real There are three arguments to DEFINE_DPM_DRAG name Re and p You supply name the name of the UDF Re and p are variables that are passed by the ANSYS FLUENT solver Release 12 0 ANSYS Inc January 26 2009 2 1 65 DEFINE Macros to your UDF Your UDF will need to return the real value of the drag force on a particle The value returned to the solver must be dimensionless and represent 18 Cd Re 24 Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following UDF named particle_drag force computes the drag f
396. f the more common errors made when interpreting source files is trying to interpret code that contains elements of C that the interpreter does not accommodate For exam ple if you have code that contains a structured reference call which is not supported by the C preprocessor the interpretation will fail and you will get an error message similar to the following Error nfs clblnx home clb fluent udfexample c line 15 structure reference Release 12 0 ANSYS Inc January 26 2009 4 5 Interpreting UDFs Release 12 0 ANSYS Inc January 26 2009 Chapter 5 Compiling UDFs After you have written your UDF s using any text editor and have saved the source file with a c extension in your working folder you are ready to compile the UDF source file build a shared library from the resulting objects and load the library into ANSYS FLUENT After being loaded the function s contained in the library will appear in drop down lists in graphical interface dialog boxes ready for you to hook to your CFD model Follow the instructions in Section 5 2 Compiling a UDF Using the GUI to compile UDF source files using the graphical user interface GUI Section 5 3 Compile a UDF Using the TUI explains how you can use the text user interface TUI to do the same The text interface option provides the added capability of allowing you to link precompiled object files derived from non ANSYS FLUENT sources e g Fortran sources to your UDF Secti
397. f_prt p dt AL real drag_factor 0 real p_relax_time cphase_state_t c amp p gt cphase Release 12 0 ANSYS Inc January 26 2009 2 203 DEFINE Macros compute particle relaxation time if P_DIAM p 0 0 drag_factor DragCoeff p c gt mu P_RHO p P_DIAM p P_DIAM p else drag_factor 133 p_relax_time 1 drag_factor check the condition and return the time step if dt gt p_relax_time 5 return p_relax_time 5 return dt Hooking a DPM Timestep UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_TIMESTEP is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable for DPM Timestep in the Discrete Phase Model dialog box in ANSYS FLUENT See Section 6 4 14 Hooking DEFINE_DPM_TIMESTEP UDFs for details on how to hook your DEFINE_DPM_TIMESTEP UDF to ANSYS FLUENT 2 204 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 15 DEFINE_DPM_VP_EQUILIB Description You can use DEFINE DPM_VP_EQUILIB to specify the equilibrium vapor pressure of vapor izing components of multicomponent particles Usage DEF INE_DPM_VP_EQUILIB name p cvap _surf Z Argument Type Description symbol name UDF name Tracked_Particle p Pointer to the Tracked_Particle data structure w
398. fer to Chapter 3 Additional Macros for Writing UDFs for a description of predefined macros such as C_T and begin_c_loop Hooking an On Demand UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE ON DEMAND is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g on_demand_calc will become visible and selectable in the Execute On Demand dialog box in ANSYS FLU ENT See Section 6 1 6 Hooking DEFINE_ON_DEMAND UDFs for details 2 22 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros 2 2 10 DEFINE_RW_FILE Description DEFINE_RW_FILE is a general purpose macro that you can use to specify customized in formation that is to be written to a case or data file or read from a case or data file You can save and restore custom variables of any data type e g integer real CXBoolean structure using DEFINE_RW_FILE It is often useful to save dynamic information e g number of occurrences in conditional sampling while your solution is being calculated which is another use of this function Note that the read order and the write order must be the same when you use this function Usage DEF INE_RW_FILE name fp Argument Type Description symbol name UDF name FILE fp Pointer to the file you are reading or writing Function returns void There are two arguments to DEFINE_
399. ference guide 2 135 multiphase flow getting domain pointer 3 32 Multiphase Model dialog box 6 55 multiphase models Eulerian property UDFs 2 87 Mixture property UDFs 2 87 VOF property UDFs 2 87 multiphase UDFs cavitation parameters 2 87 cavitation rate 2 137 data structures 1 17 data types 1 17 Release 12 0 ANSYS Inc January 26 2009 DEFINE macros 1 17 density compressible liquids 2 87 domains 1 17 drag coefficient 2 139 elasticity modulus 2 87 Eulerian model C 5 C 8 C 10 C 13 exchange property 2 139 frictional properties 2 87 granular properties 2 87 heat transfer coefficient 2 87 heterogeneous reaction rate 2 144 hooking to ANSYS FLUENT 6 55 lift coefficient 2 139 mass transfer 2 149 material properties 2 87 Mixture model C 3 net mass transfer rate 2 139 particle or droplet diameter 2 87 radial distribution 2 87 slip velocity 2 151 solids pressure 2 87 speed of sound 2 87 surface tension coefficient 2 87 threads 1 17 vector exchange property 2 151 VOF model C 1 writing 1 17 multiphase variables macros for accessing 3 22 MULTIPLE COMPUTE_NODE_P 7 17 myid 7 35 N_DOT 2 122 N_ REQ_UDM 2 197 N_TIME 3 76 N_UDM 3 80 N_UDS 3 46 3 80 ND_DOT 3 73 ND_ND 2 18 2 74 2 75 2 79 2 101 2 115 2 117 2 122 3 70 ND SET 3 70 ND_SUM 2 18 2 19 3 60 3 70 NNULLP 2 156 2 168 2 190 3 81 Node data structure 1 10 Index 11 Index node index number
400. ffset from which the library may use the UDMs It should be saved as a global integer such as offset in the UDF and it should be initialized to the special variable UDM_UNRESERVED offset Reserve_User_Memory_Vars int num Reserve User Memory Vars defined in sg_udms h is designed to be called from an EXECUTE_ON_LOADING UDF Section 2 2 6 DEFINE_EXECUTE_ON_LOADING An on loading UDF as its name implies executes as soon as the shared library is loaded into ANSYS FLUENT The macro can also be called from an INIT or ON_DEMAND UDF although this is discouraged except for testing purposes After a UDM is reserved it can be set to unique names for the particular library using Set User Memory Name see below for de tails After the number of UDMs that are needed by a particular library is set in the GUI and the UDMs are successfully reserved for the loaded library the other functions in the library can safely use C_LUDMI c t offset up to C_UDMI c t offset num 1 to store values in memory locations without interference Two example source code files named udm_res1 c and udm_res2 c each containing two UDFs are listed below The first UDF is an EXECUTE_ON_LOADING UDF that is used to reserve UDMs for the library and set unique names for the UDM locations so that they can be easily identified in postpro cessing The second UDF is an ON_DEMAND UDF that is used to set the values of the UDM locations after the solution has been initialized The ON_DEMA
401. file User Defined Init Solve U Momentum Solve V lomentum Solve W Momentum Solve Mass Continuity Update Velocity Solve Energy onvergence Solve Turbulence Equation s Solve Other Transport Equations as required Update Properties including User Defined Properties Figure 1 9 1 Solution Procedure for the Pressure Based Segregated Solver 1 14 Release 12 0 ANSYS Inc January 26 2009 1 9 UDF Calling Sequence in the Solution Process User Defined Profile User Defined Init Solve Mass amp Momentum Solve Energy onvergence Solve Turbulence Equation s Solve Other Transport Equations as required Update Properties including User Defined Properties Figure 1 9 2 Solution Procedure for the Pressure Based Coupled Solver Release 12 0 ANSYS Inc January 26 2009 1 15 Overview User Defined Profile User Defined Init Solve Mass Momentum Energy amp Species onvergence Solve Turbulence Equation s Solve Other Transport Equations as required Update Properties including User Defined Properties Figure 1 9 3 Solution Procedure for the Density Based Solver 1 16 Release 12 0 ANSYS Inc January 26 2009 1 10 Special Considerations for Multiphase UDFs 1 10 Special Considerations for Multiphase UDFs In many cases the UDF source code that you will write for a single phase flow will be the same as for a mul
402. file from ANSYS FLUENT It will specify the customized section that is to be written to the data file To hook a read case file UDF for example click the Edit button next to Read Case to open the Read Case Functions dialog box Figure 6 1 12 Read Case Functions Available Read Case Functions 3 E selected Read Case Functions E E Avallable Read Case Fi SS 36 H a reader2 libudf reader 1 libudf Figure 6 1 12 The Read Case Functions Dialog Box Select the function s you wish to hook to your model from the Available Read Case Functions list Click Add and then OK to close the dialog box The name of the function you selected will be displayed in the Read Case field of the User Defined Function Hooks dialog box If you select more than one function the number will be displayed e g 2 selected Click OK in the User Defined Function Hooks dialog box to apply the settings See Section 2 2 10 DEFINE_RW_FILE for details about defining DEFINE_RW_FILE functions 6 12 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 1 8 User Defined Memory Storage You can store values computed by your UDF in memory so that they can be retrieved later either by a UDF or for postprocessing within ANSYS FLUENT In order to have access to this memory you will need to allocate memory by specifying the Number of User Defined Memory Locations in the User Defined Memory dialog box Figure 6 1 13
403. fine H20 2 define NUM_SPECS 3 Reaction Exponents define HF_EXP 2 0 define WF6_EXP 0 0 define H20_EXP 0 0 define MW_H2 2 0 define STOIC_H2 3 0 Reaction Rate Routine real reaction_rate cell_t c Thread cthread real mw real yi Note that all arguments in the reaction_rate function call in your c source file MUST be on the same line or a compilation error will occur of real concenHF C_R c cthread yi HF mw HF return arrhenius_rate C_T c cthread pow concenHF HF_EXP DEFINE_SR_RATE arrhenius f fthread r mw yi rr rr reaction_rate F_CO f fthread THREAD_TO fthread mw yi 2 1 16 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example 2 Surface Reaction Rate Using Site Species The following compiled UDF named my_rate defines a custom surface reaction rate that takes into account site species ATCC CCL OL ert oL error Tre orrrrrroerrcr rrr reo rerre rere errr rere rs S Custom surface reaction rate UDF EOC OCGA OA OOOO AAAI RIA E A I a A ak kk a kk include udf h DEFINE_SR_RATE my_rate f t r mw yi rr Thread t0O t gt t0 cell_t c0 F_CO f t real sih4 yi 0 mass fraction of sih4 at the wall real si2h6 yil1 real sih2 yi 2 real h2 yil3l real ar yi 4 mass fraction of ar at the wall real rho_w 1 0 site_rho 1 0e 6 T_w 300 0 real si_s yil6 site fraction of si_s real
404. for the mixture of phases using DEFINE_SOURCE when the mixture model is used but not for the Eulerian model For the latter case you can specify momentum sources for the individual phases Hence the multiphase model as well as the term being modified by the UDF determines which domain or thread is required 1 18 Release 12 0 ANSYS Inc January 26 2009 1 10 Special Considerations for Multiphase UDFs UDFs that are hooked to the mixture of phases are passed superdomain or mixture level structures while functions that are hooked to a particular phase are passed subdomain or phase level structures DEFINE_ADJUST and DEFINE_INIT UDFs are hardwired to the mixture level domain Other types of UDFs are hooked to different phase domains For your convenience Appendix B contains a list of multiphase models in ANSYS FLUENT and the phase on which UDF are specified for the given variables From this information you can infer which domain structure is passed from the solver to the UDF Release 12 0 ANSYS Inc January 26 2009 1 19 Overview 1 20 Release 12 0 ANSYS Inc January 26 2009 Chapter 2 DEFINE Macros This chapter contains descriptions of predefined DEFINE macros that you will use to define your UDF The chapter is organized in the following sections e Section 2 1 Introduction e Section 2 2 General Purpose DEFINE Macros e Section 2 3 Model Specific DEFINE Macros e Section 2 4 Multiphase DEFINE Mac
405. g libudf Copy makefile udf2 from path ansys_inc v120 fluent fluent12 0 2 src maket ile udf2 to the library directory e g libudf and name it Makefile Note that path is the directory in which you have installed ANSYS FLUENT and x is replaced by the appropriate number for the release e g 9 for fluent12 0 9 In the library directory you just created in Step 1 make a directory that will store your source file and name it src Copy your source file e g myudf c to the source directory src Copy makefile udf from path ansys_inc v120 fluent fluent12 0 src makefile udf to the src directory and name it makefile Note that path is the directory in which you have installed ANSYS FLUENT and x is replaced by the appropriate number for the release e g 9 for fluent12 0 9 Identify the architecture name of the machine on which you are running e g ultra This can be done by either typing the command fluent arch in the ANSYS FLUENT TUI window or running the ANSYS FLUENT utility program fluent_arch at the command line of a UNIX shell Note that if you are running a 64 bit version of ANSYS FLUENT the ar chitecture name will have a _64 appended to it e g ultra_64 In the library directory e g libudf create an architecture directory that is named after the architecture identifier determined in the previous step e g ultra Release 12 0 ANSYS Inc January 26 2009 5 3 C
406. g cell_viscosity libudf from the list of UDFs displayed in the User Defined Functions dialog box and click OK The name of the function will subsequently be displayed under the selected property in the Create Edit Materials dialog box Release 12 0 ANSYS Inc January 26 2009 6 37 Hooking UDFs to ANSYS FLUENT User Defined Fu cell viscosity Figure 6 2 21 The User Defined Functions Dialog Box i If you plan to define density using a UDF note that the solution conver gence will become poor as the density variation becomes large Specifying a compressible law density as a function of pressure or multiphase behav ior spatially varying density may lead to divergence It is recommended that you restrict the use of UDFs for density to weakly compressible flows with mild density variations See Section 2 3 16 DEFINE PROPERTY UDFs for details about DEFINE PROPERTY functions 6 2 17 Hooking DEFINE SCAT PHASE FUNC UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SCAT_PHASE_FUNC UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Func tions dialog box in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first make sure that the Discrete Ordinates DO model is selected in the Radiation Model dialog box Then open the Materials task page lt BWeiarlS Select the ap
407. g Box In the Select File dialog box select the desired file e g udfexample c you want to compile The complete path to the source file will then be displayed under Source File s Click OK The Select File dialog box will close and the file you added will appear in the Source Files list in the Compiled UDFs dialog box In a similar manner select the Header Files that need to be included in the compi lation 4 In the Compiled UDFs dialog box type the name of the shared library in the Library Name field or leave the default name libudf Click Build This process will compile the code and will build a shared library in your working folder for the architecture you are running on As the compile build process begins a Warning dialog box will appear reminding you that the UDF source file must be in the folder that contains your case and data 8 10 Release 12 0 ANSYS Inc January 26 2009 8 1 Step By Step UDF Example files i e your working folder If you have an existing library folder e g libudf then you will need to remove it prior to the build to ensure that the latest files are used Click OK to close the dialog box and resume the compile build process The results of the build will be displayed in the console You can view the compilation history in the log file that is saved in your working folder If the compile build is unsuccessful then ANSYS FLUENT will report an error and you will need to debug your program
408. g UDFs and using them in your ANSYS FLUENT model This document does not imply responsibility on the part of ANSYS Inc for the ac curacy or stability of solutions obtained using UDFs that are either user generated or provided by ANSYS Inc Support for current license holders will be limited to guidance related to communication between a UDF and the ANSYS FLUENT solver Other aspects of the UDF development process that include conceptual function design implementation writing C code compilation and debugging of C source code execution of the UDF and function design verification will remain the re sponsibility of the UDF author UDF compiled libraries are specific to the computer architecture being used and the version of the ANSYS FLUENT executable being run and must be rebuilt any Release 12 0 ANSYS Inc January 26 2009 l About This Document time ANSYS FLUENT is upgraded your operating system changes or the job is run on a different type of computer Note that UDFs may need to be updated with new versions of ANSYS FLUENT ll Release 12 0 ANSYS Inc January 26 2009 Chapter 1 Overview This chapter contains an overview of user defined functions UDFs and their usage in ANSYS FLUENT Details about UDF functionality are described in the following sections e Section 1 1 What is a User Defined Function UDF e Section 1 2 Why Use UDFs e Section 1 3 Limitations e Section 1 4 Defining Your UDF Using DEFINE M
409. g and the compilation is successful then the CPP Command Name that was executed will be displayed the console If the compilation is unsuccessful then ANSYS FLUENT will report an error and you will need to debug your program See Section 4 3 Common Errors Made While Interpret ing A Source File You can also view the compilation history in the log file that is saved in your working folder f Close the Interpreted UDFs Dialog Box when the interpreter has finished 5 Write the case file The interpreted function s will be saved with the case file and automatically interpreted when the case file is subsequently read 4 3 Common Errors Made While Interpreting A Source File If there are compilation errors when you interpret a UDF source file they will appear in the console However you may not see all the error messages if they scroll off the screen too quickly For this reason you may want to disable the Display Assembly Listing option while debugging your UDF You can view the compilation history in the log file that is saved in your working folder If you keep the Interpreted UDFs dialog box open while you are in the process of debugging your UDF the Interpret button can be used repeatedly since you can make changes with an editor in a separate window Then you can continue to debug and interpret until no errors are reported Remember to save changes to the source code file in the editor window before trying to interpret again One o
410. gramming practice to do so The macro PRINCIPAL_FACE_P is used to ensure that faces at partition boundaries are not counted twice see Section 7 2 Cells and Faces in a Partitioned Mesh The nodes display the total area and force on the monitors using the Message utility before the global summation PRF_GRSUM1 Section 7 5 4 Global Reduction Macros is a global summation macro that is used to compute the total area and force of all the compute nodes These operations are directed for the compute nodes using if RP_NODE Release 12 0 ANSYS Inc January 26 2009 7 39 Parallel Considerations 7 9 Writing Files in Parallel Although compute nodes can perform computations on data simultaneously when ANSYS FLUENT is running in parallel when data is written to a single common file the writing operations have to be sequential The file has to be opened and written to by processes that have access to the desired file system It is often the case that the compute nodes are running on a dedicated parallel machine without disk space This means that all of the data has to be written from the host process which always runs on a machine with access to a file system since it reads and writes the case and data files This implies that unlike the example in Section 7 5 8 Message Passing Macros where data is only passed to compute node 0 to be collated data must now be passed from all the compute nodes to compute node 0 which then passes it on to the
411. graphical user interface GUI in ANSYS FLUENT The GUI option for compiling a source file on a Windows system is discussed below For details about compiling on other platforms using the TUI to compile your function or for general questions about compiling UDFs in ANSYS FLUENT see Chapter 5 Compiling UDFs 1 As mentioned previously make sure that you have started ANSYS FLUENT in Win dows using FLUENT Launcher with the following settings e Specify the folder that contains your case data and UDF source files in the Working Directory text box in the General Options tab e Make sure that the batch file for the UDF compilation environment settings is correctly specified in the UDF Compiler tab see Section 5 1 2 Compilers for further details 2 Open the Compiled UDFs dialog box Figure 8 1 6 Define User Defined Functions Compiled Compiled UDFs Source Files 0 a Header Files Library Name libudF Figure 8 1 6 The Compiled UDFs Dialog Box Release 12 0 ANSYS Inc January 26 2009 8 9 Examples 3 Click Add under Source Files in the Compiled UDFs dialog box This will open the Select File dialog box Figure 8 1 7 Select File O mywork 2 My Recent Documents kot on LEBKTHOMP My Network Files of type Source Files Source File s Z mywork udfexample c Figure 8 1 7 The Select File Dialo
412. hase s primary and secondary phase s mixture mixture mixture mixture mixture mixture primary and secondary phase s primary and secondary phase s mixture mixture primary and secondary phase s primary and secondary phase s Wall species boundary condition shear stress components moving velocity components temperature heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream temperature DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE phase dependent primary and secondary phase s mixture mixture mixture mixture mixture mixture mixture mixture Release 12 0 ANSYS Inc January 26 2009 Quick Reference Guide for Multiphase DEFINE Macros Table C 4 3 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flow Variable Macro Phase Specified On Wall continued granular flux granular temperature discrete phase boundary condition user defined scalar boundary value DEF INE_PROFILE DEFINE PROFILE DEFINE_DPM_BC DEFINE_PROFILE secondary phase s secondary phase s secondary phase s secondary phase s Material Properties granular diameter granular viscosity granular bulk viscosity granular frictional viscosity granular conductivity granula
413. he solution has been initialized The ON DEMAND UDF sets the initial values of the UDM locations using udm_offset which is defined in the on loading UDF Note that the on demand UDF must be executed after the solution is initialized to reset the initial values for the UDMs See Sections 3 2 9 and 3 2 9 for more information on reserving and naming UDMs paaa ooo o kkk A A A A kk KK kk kkk kkk kkk kkk kk kk This file contains two UDFs an execute on loading UDF that reserves three UDMs for libudf and renames the UDMs to enhance postprocessing and an on demand UDF that sets the initial value of the UDMs BE oo ooo kkk AA 2A 2k 2k kkk kkk kkk include udf h define NUM_UDM 3 static int udm_offset UDM_UNRESERVED DEFINE_EXECUTE_ON_LOADING on_loading libname if udm_offset UDM_UNRESERVED udm_offset 2 14 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Reserve_User_Memory_Vars NUM_UDM if udm_offset UDM_UNRESERVED Message nYou need to define up to 4d extra UDMs in GUI and then reload current library s n NUM_UDM libname else Message d UDMs have been reserved by the current library s n NUM_UDM libname Set_User_Memory_Name udm_offset lib1 UDM 0 Set_User_Memory_Name udm_offset 1 lib1 UDM 1 Set_User_Memory_Name udm_offset 2 lib1 UDM 2 Message nUDM Offset for Current Loaded Library d udm_offset DEFINE_ON_DEMAND set_udms
414. hen the function will return a value of 1 Note that the domain_id that is returned by the macro is the same integer ID that is displayed in the graphical user interface when you select the desired phase in the Phases task page in ANSYS FLUENT Domain subdomain int domain_id DOMAIN_ID subdomain Phase Domain Index PHASE DOMAIN INDEX The PHASE DOMAIN_INDEX macro retrieves the phase domain index for a given phase level domain subdomain pointer PHASE_DOMAIN_INDEX has one argument subdomain which is the pointer to a phase level domain phase_domain_index is an index of subdo main pointers It is an integer that starts with 0 for the primary phase and is incremented by one for each secondary phase Domain subdomain int phase_domain_index PHASE_DOMAIN_INDEX subdomain 3 68 Release 12 0 ANSYS Inc January 26 2009 3 4 Vector and Dimension Macros 3 4 Vector and Dimension Macros ANSYS FLUENT provides some utilities that you can use in your UDFs to access or manipulate vector quantities and deal with two and three dimensions These utilities are implemented as macros in the code There is a naming convention for vector utility macros V denotes a vector S denotes a scalar and D denotes a sequence of three vector components of which the third is always ignored for a two dimensional calculation The standard order of operations convention of parentheses exponents multiplication division addition and subtraction
415. hey are anal ogous to do loops in FORTRAN The format of a for loop is for begin end increment statements where begin is the expression that is executed at the beginning of the loop end is the logical expression that tests for loop termination and increment is the expression that is executed at the end of the loop iteration usually incrementing a counter Example Print integers 1 10 and their squares int i j n 10 for i 1 i lt n i j i i printf fd d n i j Release 12 0 ANSYS Inc January 26 2009 A 11 C Programming Basics The equivalent FORTRAN code is shown below for comparison INTEGER I J N 10 DO I 1 10 J I I WRITE I J ENDDO A 12 Common C Operators Operators are internal C functions that when they are applied to values produce a result Common types of C operators are arithmetic and logical A 12 1 Arithmetic Operators Some common arithmetic operators are listed below assignment addition subtraction multiplication division modulo reduction increment decrement Note that multiplication division and modulo reduction operations will be performed before addition and subtraction in any expression When division is performed on two integers the result is an integer with the remainder discarded Modulo reduction is the remainder from integer division The operator is a shorthand notation for the increment operation
416. hich contains data related to the particle being tracked real cvap_surf Array that contains the equilibrium vapor concentration Z Compressibilty Z over the particle surface Function returns void There are three arguments to DEFINE DPM VP_EQUILIB name p and cvap_surf You supply the name of your user defined function p is passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the equilibrium vapor concentrations and store the values in cvap surf Example The following UDF named raoult_vpe computes the equilibrium vapor concentration of a multicomponent particle using the Raoult law The vapor pressure in the law is proportional to the molar fraction of the condenses material DEFINE_VP_EQUILIB is called several times every particle time step in ANSYS FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UDF Release 12 0 ANSYS Inc January 26 2009 2 205 DEFINE Macros POR o o kkk kk kkk kk kkk kkk kk kk kk kkk kk kk kk kkk kk 4 4 k UDF for defining the vapor particle equilibrium for multicomponent particles EEEE ooo oo k kkk k kkk kkk kk kk include lt udf h gt DEFINE_DPM_VP_EQUILIB raoult_vpe p cvap_surf Z int is real molwt MAX_SPE_EQNS Thread tO P_CELL_THREAD p cell thread of particle location Material gas_mix THREAD_MATERIAL tO gas mixture material Material cond_mix P_MATERIAL p
417. his section are used to set parameters for a particular model in ANSYS FLUENT Table 2 3 Table 2 3 5 provides a quick reference guide to the DEFINE macros the functions they are used to define and the dialog boxes where they are activated in ANSYS FLUENT Definitions of each DEFINE macro are listed in udf h For your convenience they are listed in Appendix B Section 2 3 1 Section 2 3 2 Section 2 3 3 Section 2 3 4 Section 2 3 5 Section 2 3 6 Section 2 3 7 Section 2 3 8 Section 2 3 9 Section 2 3 10 Section 2 3 11 Section 2 3 12 Section 2 3 13 Section 2 3 14 Section 2 3 15 Section 2 3 16 Section 2 3 17 Section 2 3 18 Section 2 3 19 Section 2 3 20 Section 2 3 21 Release 12 0 ANSYS Inc January 26 2009 DEF INE_CHEM_STEP DEF INE_CPHI DEFINE DIFFUSIVITY DEF INE_DOM_DIFFUSE_REFLECTIVITY DEF INE_DOM_SOURCE DEFINE _DOM_SPECULAR_REFLECTIVITY DEFINE_EMISSIVITY_WEIGHTING_FACTOR DEF INE_GRAY_BAND_ABS_COEFF DEFINE HEAT FLUX DEF INE_IGNITE_SOURCE DEFINE_NET_REACTION_RATE DEFINE NOX_RATE DEFINE PR_RATE DEFINE_PRANDTL UDF s DEF INE_PROFILE DEFINE PROPERTY UDF s DEF INE_SCAT_PHASE_FUNC DEFINE_SOLAR_INTENSITY DEFINE SOURCE DEFINE_SOX_RATE DEF INE_SPECIFIC_HEAT 2 25 DEFINE Macros Section 2 3 22 Section 2 3 23 Section 2 3 24 Section 2 3 25 Section 2 3 26 Section 2 3 27 Section 2 3 28 DEFINE_SR_RATE DEFINE TRANS UDFs DEF INE_TURB_PREMIX_SOURCE DEFINE_TURB_SCHM
418. hrough any graphics dialog boxes In stead ANSYS FLUENT searches the newly loaded library for any UDFs of the type EXECUTE_AFTER_CASE or EXECUTE_AFTER_DATA and will automatically execute them in the order they appear in the library Release 12 0 ANSYS Inc January 26 2009 2 17 DEFINE Macros 2 2 8 DEFINE_INIT Description DEFINE_INIT is a general purpose macro that you can use to specify a set of initial values for your solution DEFINE_INIT accomplishes the same result as patching but does it in a different way by means of a UDF A DEFINE_INIT function is executed once per initialization and is called immediately after the default initialization is performed by the solver Since it is called after the flow field is initialized it is typically used to set initial values of flow quantities For an overview of the ANSYS FLUENT solution process which shows when a DEFINE_INIT UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 Usage DEFINE_INIT name d Argument Type Description symbol name UDF name Domain d Pointer to the domain over which the initialization function is to be applied The domain argument provides access to all cell and face threads in the mesh For multiphase flows the pointer that is passed to the function by the solver is the mixture level domain Function returns void There are two arguments to DEFINE_INIT name and d You supply name the name of the UDF d is passed from the ANSYS FLUENT so
419. i1 psat double constants 8 7 4192420 2 97221E 1 1 155286E 1 8 68563E 3 1 094098E 3 4 39993E 3 2 520658E 3 5 218684E 4 vari is an expression that is used in the summation loop vari PSAT_A tsat PSAT_TP Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros Compute summation loop i 0 sumi 0 0 while i lt C_LOOP sumi constants Li pow var1 i i ans1 sum1 H20_TC tsat 1 0 compute exponential to determine result psat has units of Pascals psat H20_PC exp ans1 return psat J DEFINE_HET_RXN_RATE user_evap_condens_react c t hr mw yi rr rr_t Thread pt THREAD_SUB_THREADS t Thread tp pt 0 Thread ts pt 1 int i real concentration_evap_primary accum 0 mole_frac_evap_prin concentration_sat real T_prim C_T c tp primary phase gas temperature real T_sec C_T c ts secondary phase droplet temperature real diam C_PHASE_DIAMETER c ts secondary phase diameter real D_evap_prim C_DIFF_EFF c tp index_evap_primary 0 7 C_MU_T c tp C_R c tp primary phase species turbulent diffusivity real Re Sc Nu urel urelx urely urelz 0 mass_coeff area_density flux_evap if Data_Valid_P urelx C_U c tp C_U c ts urely C_V c tp C_V c ts if RP_3D urelz C_W c tp C_W c ts endif Release 12 0 ANSYS Inc January 26 2009 2 1 47 DEFINE Macros urel
420. ialization UDFs overwrite initialization values that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next momentum equations for u v and w velocities are solved sequentially followed by mass continuity and velocity updates Subsequently the energy and species equations are solved followed by turbulence and other scalar transport equations as required Note that PROFILE and SOURCE UDF are called by each Solve routine for the variable currently under consideration e g species velocity After the conservation equations properties are updated including PROPERTY UDFs Thus if your model involves the gas law for example the density will be updated at this time using the updated temperature and pressure and or species mass fractions A check for either convergence or additional requested iterations is done and the loop either continues or stops 1 12 Release 12 0 ANSYS Inc January 26 2009 1 9 UDF Calling Sequence in the Solution Process Pressure Based Coupled Solver The solution process for the pressure based coupled solver Figure 1 9 2 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the ANSYS FLUENT user interface Next PROFILE UDFs are called followed by a call to INIT UDFs Initialization UDFs overwrite initialization va
421. ialog box Figure 6 2 1 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first set up the species transport and combustion models in the Species Model dialog box gt A Beets Edit Release 12 0 ANSYS Inc January 26 2009 6 13 Hooking UDFs to ANSYS FLUENT Note that chemistry step UDFs may only be used with the laminar finite rate model with stiff chemistry enabled the EDC model or the PDF Transport model Therefore you must use one of the following groups of settings in the Species Model dialog box e To enable the laminar finite rate model select Species Transport enable Volumetric in the Reactions group box select Laminar Finite Rate in the Turbulence Chemistry Interaction group box and enable Stiff Chemistry Solver in the Options group box e To enable the EDC model select Species Transport enable Volumetric in the Re actions group box and select Eddy Dissipation Concept in the Turbulence Chemistry Interaction group box e To enable the PDF Transport model select Composition PDF Transport and enable Volumetric in the Reactions group box Next open the User Defined Function Hooks dialog box Figure 6 2 1 Define User Defined gt Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall H
422. ib and object libudf exp Done 9 In the Compiled UDFs dialog box Figure 5 2 3 load the shared library that was just built into ANSYS FLUENT by clicking Load A message will be displayed on the console providing a status of the load process For example Z mywork Opening library libudf Library libudf ntx86 2d libudf d1l1 opened inlet_x_velocity Done indicates that the shared library named libudf was successfully loaded on a Win dows machine and it contains one function named inlet_x_velocity i Note that compiled UDFs are displayed in ANSYS FLUENT dialog boxes with the associated UDF library name using the identifier For exam ple a compiled UDF named inlet_x_velocity that is associated with a shared library named libudf will appear in ANSYS FLUENT dialog boxes as inlet_x_velocity libudf This visually distinguishes UDFs that are compiled from those that are interpreted After the compiled UDF s become visible and selectable in graphics dialog boxes in ANSYS FLUENT they can be hooked to your model See Chapter 6 Hooking UDFs to ANSYS FLUENT for details You can use the UDF Library Manager dialog box to unload the shared library if desired See Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box for details 10 Write the case file if you want the compiled function s in the shared library to be saved with the case The functions will be loaded automatically into ANSYS FL
423. ick OK If you forget to enable the sharing option for the folder using Windows Explorer then ANSYS FLUENT will hang when you try to load the library in the Compiled UDFs dialog box 2 For UNIX Linux start ANSYS FLUENT from the directory that contains your case data and UDF source files For Windows start ANSYS FLUENT using FLUENT Launcher with the following settings e Specify the folder that contains your case data and UDF source files in the Working Directory text box in the General Options tab e Make sure that the batch file for the UDF compilation environment settings is correctly specified in the UDF Compiler tab see Section 5 1 2 Compilers for further details 3 Read or set up your case file Release 12 0 ANSYS Inc January 26 2009 5 5 Compiling UDFs 4 Open the Compiled UDFs dialog box Figure 5 2 1 Define gt User Defined Functions gt Compiled Compiled UDFs Source Files B O Header Files Library Name bud Figure 5 2 1 The Compiled UDFs Dialog Box 5 In the Compiled UDFs dialog box click on Add under Source Files to select the UDF source file or files you want to compile This will open the Select File dialog box shown in Figure 5 2 2 6 In the Select File dialog box click the names of all of the desired files e g udfex ample c so that the complete paths to the source files are displayed under Source File
424. id that is accounted for by default is conduction With the inclusion of radiation effects radiative heat transfer to and from the wall must also be accounted for This is done automatically if you use ANSYS FLUENT s built in P1 model The DEFINE_ HEAT_FLUX macro allows the wall boundary condition to be modified to accommodate this second mode of heat transfer by specifying the coefficients of the gir equation discussed in Section 2 3 9 DEFINE HEAT_FLUX The net 8 44 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples radiative heat flux to the wall has already been given as Equation 8 2 9 Comparing this equation with that for gir in Section 2 3 9 DEFINE_HEAT_FLUX will result in the proper coefficients for cir In this example the implementation of the P1 model can be accomplished through six separate UDFs They are all included in a single source file which can be executed as a compiled UDF The single user defined scalar transport equation for incident radiation G uses a DEFINE_DIFFUSIVITY UDF to define I of Equation 8 2 6 and a UDF to define the source term of Equation 8 2 7 The boundary condition for G at the walls is handled by assigning in DEFINE PROFILE the negative of Equation 8 2 11 as the specified flux A DEFINE_ADJUST UDF is used to instruct ANSYS FLUENT to check that the proper number of user defined scalars has been defined in the solver Lastly the energy equation must be assigned a source ter
425. ield is not divergence free then is not conserved and will result in overshoots undershoots in the cell value of You will need to compute Y in your UDF using for example predefined macros for ve locity vector and scalar density that ANSYS FLUENT has provided see Chapter 3 Ad ditional Macros for Writing UDFs or using your own prescription The first case is illustrated in the sample C source code shown below i Note that if more than one scalar is being solved you can use a conditional if statement in your UDF to define a different flux function for each i i 0 is associated with scalar 0 the first scalar equation being solved Fal Note also that A must have units of mass flow rate in SI i e kg s Release 12 0 ANSYS Inc January 26 2009 2 231 DEFINE Macros POR o ooo kkk kk A A A kk 1 21 kkk kk A A A kkk kkk kk k sample C source code that computes dot product of psi and A Note that this is not a complete C function BE EEEo ooo o kkk k kkk kkk kkk real NV_VEC psi NV_VEC A declaring vectors psi and A defining psi in terms of velocity field NV_D psi F_U f t F_V f t F_W f t NV_S psi F_R f t multiplying density to get psi vector F_AREA A f t face normal vector returned from F_AREA return NV_DOT psi A dot product of the two returned Additionally since most quantities in ANSYS FLUENT are not allocated in memory for interior faces only f
426. if the face is in the interior of the domain then both cO and c1 exist There are two macros THREAD_TO t and THREAD_T1 t that can be used to identify cell threads that are adjacent to a given face f in a face thread t THREAD_TO expands to a function that returns the cell thread of a given face s adjacent cell c0 and THREAD_T1 returns the cell thread for c1 if it exists Table 3 2 25 Adjacent Cell Thread Macros Defined in mem h Macro Argument Types Returns THREAD_TO t Thread t cell thread pointer for cell c0 THREAD_T1 t Thread t cell thread pointer for cell c1 Interior Face Geometry INTERIOR FACE GEOMETRY INTERIOR FACE GEOMETRY f t A ds es A by_es dr0 dri expands to a function that outputs the following variables to the solver for a given face f on face thread t The macro is defined in the sg h header file which is not included in udf h You will need to include this file in your UDF using the include directive real A ND_ND the area normal vector real ds distance between the cell centroids real es ND_ND the unit normal vector in the direction from cell c0 to cl real A by_es the value zs real drO ND_ND vector that connects the centroid of cell cO to the face centroid real dri ND ND the vector that connects the centroid of cell c1 to the face centroid Note that INTERIOR_FACE_GEOMETRY can be called to retrieve some of the terms needed to evaluate Equations 3 2 1 and 3 2 3 Bound
427. ile is an array of data your UDF will need to create the pressure array by looping over all faces in the boundary zone and for each face set the pressure value using F_PROFILE In the sample UDF source code shown below the y coordinate of the centroid is obtained using F_CENTROID and this value is used in the pressure calculation that is stored for each face The solver passes the UDF the right index to the pressure variable because the UDF is hooked to Gauge Total Pressure in the Pressure Inlet boundary condition dialog box See Section 2 3 15 DEFINE_PROFILE for more information on DEFINE_PROFILE UDFs 3 34 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros J PK k k kk OO I IR I 3K 2K K FK FK 2K K FK 2K 2K 2K 2 2K K FK FK 2K 2k FK 2k K K 2 2k K 2k 2k 2k K FK 2K 2 2k 2 2k 2k K UDF for specifying a parabolic pressure profile boundary profile BORA ooo o kkk 21 1 kkk kkk kkk include udf h DEFINE_PROFILE pressure_profile t i real x ND_ND this will hold the position vector real y face_t f begin_f_loop f t F_CENTROID x f t y x 1 F_PROFILE f t i 1 1e5 y y 0745 0745 0 1e5 J end_f_loop f t THREAD SHADOW t THREAD_SHADOW returns the face thread that is the shadow of Thread t if it is one of a face face shadow pair that comprise a thin wall It returns NULL if the boundary is not part of a thin wall and is often used in an if statement such as if NULLP ts THREAD_SH
428. ils Release 12 0 ANSYS Inc January 26 2009 2 1 25 DEFINE Macros Table 2 3 6 Eulerian Multiphase Model and DEFINE_TURBULENT_VISCOSITY UDF Usage Turbulence Model Phase that Turbulent Viscosity UDF Is Specified On k e Mixture k e Dispersed k e Per Phase mixture primary and secondary phases primary and secondary phases primary and secondary phases Usage DEF INE_TURBULENT_VISCOSITY name c t Argument Type Description symbol name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the turbulent viscosity is to be applied Function returns real There are three arguments to DEFINE_TURBULENT_VISCOSITY name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value of the turbulent viscosity to the solver Example 1 Single Phase Turbulent Viscosity UDF The following UDF named user _mu_t defines a custom turbulent viscosity for the stan dard k e turbulence model Note that the value of M keCmu in the example is defined through the graphical user interface but made accessible to all UDFs The source code can be interpreted or compiled in ANSYS FLUENT 2 126 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros POR oo ooo o kkk kkk kkk kkk kk kkk kk UDF that specifies a custom turbulent viscosity for standar
429. imums and minimums and global logicals These macros begin with the prefix PRF_G and are defined in prf h Global summation macros are identified by the suffix SUM global maximums by HIGH and global minimums by LOW The suffixes AND and OR identify global logicals The variable data types for each macro are identified in the macro name where R denotes real data types I denotes integers and L denotes logicals For example the macro PRF_GISUM finds the summation of integers over the compute nodes Each of the global reduction macros discussed in the following sections has two different versions one takes a single variable argument while the other takes a variable array Macros with a 1 appended to the end of the name take one argument and return a single variable as the global reduction result For example the macro PRF_GIHIGH1 x expands to a function that takes one argument x and computes the maximum of the variable x amongst all of the compute nodes and returns it The result can then be assigned to another variable e g y as shown in the following example 7 18 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Example Global Reduction Variable Macro int y int x myid y PRF_GIHIGH1 x y now contains the same number compute_node_count 1 on all the nodes Macros without a 1 suffix on the other hand compute global reduction variable arrays These macros take three arguments x
430. in typical ANSYS FLUENT applications e Section 8 2 1 Boundary Conditions Section 8 2 2 Source Terms Section 8 2 3 Physical Properties Section 8 2 4 Reaction Rates Section 8 2 5 User Defined Scalars Section 8 2 6 User Defined Real Gas Models Release 12 0 ANSYS Inc January 26 2009 8 13 Examples 8 2 1 Boundary Conditions This section contains two applications of boundary condition UDFs e Parabolic Velocity Inlet Profile for an Elbow Duct e Transient Velocity Outlet Profile for Flow in a Tube Parabolic Velocity Inlet Profile in an Elbow Duct Consider the elbow duct illustrated in Figure 8 2 1 The domain has a velocity inlet on the left side and a pressure outlet at the top of the right side PRRRRERS RES Ae Coe SSS ee ee ca A Mesh FLUENT 12 0 2d pbns lam Figure 8 2 1 The Mesh for the Turbine Vane Example A flow field in which a constant x velocity is applied at the inlet will be compared with one where a parabolic x velocity profile is applied While the application of a profile using a piecewise linear profile is available with the boundary profiles option the specification of a polynomial can only be accomplished by a user defined function The results of a constant velocity of 01 m sec at the inlet are shown in Figures 8 2 2 and 8 2 3 The consistent profile is seen to develop as the flow passes through the duct 8 14 Release 12 0 ANSYS Inc J
431. ined Functions Dialog Box See Section 2 3 17 DEFINE_SCAT_PHASE_FUNC for details about DEFINE_SCAT_PHASE_FUNC functions 6 2 18 Hooking DEFINE_SOLAR_INTENSITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_SOLAR_INTENSITY UDF the name of the function you supplied in the argument of the DEFINE macro will become visible and selectable in the User Defined Functions dialog box in ANSYS FLUENT To hook the UDF first open the Radiation Model dialog box Figure 6 2 24 6 40 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs Vere CRAE Edit Radiation Model Model Iteration Parameters Ooff Flow Iterations per Radiation Iteration a i e al O Rosseland OP1 EARR O Discrete Transfer DTRM Angular Discretization Surface to Surface 525 Theta Divisions gt SS Discrete Ordinates DO a v x _ Non Gray Model Number of Bands g B looo oo f P C DO Energy Coupling Phi Divisions Theta Pixels Phi Pixels Solar Load 4 v a x a 7 Model Sun Direction Vector O off Solar Ray Tracing fi O DO Irradiation Use Direction Computed from Solar Calculator Solar Calculator Illumination Parameters Direct Solar Irradiation wjm2 Diffuse Solar Irradiation wim2 Spectral Fraction V I
432. ing Model Specific UDFs 6 2 25 Hooking DEFINE_TURB_SCHMIDT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_TURB_SCHMIDT UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT To hook the UDF first open the Viscous Model dialog box Figure 6 2 34 and set up a turbulence model i If you select k epsilon from the Model list you must not select RNG from the k epsilon Model list gt DES Meta Eai Viscous Model Model Model Constants O Inviscid mu O Laminar 0 09 Spalart Allmaras 1 eqn k epsilon 2 eqn C1 Epsiion Ok omega 2 eqn E O Transition k kl omega 3 eqn O Transition SST 4 eqn C2 Epsfion O Reynolds Stress 7 eqn T Detached Eddy Simulation Ov Large Eddy Simulation LES TKE Prandtl Number k epsilon Model 1 O Standard ORNG User Defined Functions ORealizable Turbulent Viscosity Near Wall Treatment none Standard Wall Functions Prandtl and Schmidt Numbers O Non Equilibrium Wall Functions Turbulent Schmidt Number O Frhanced wal Treatment CI ae O User Defined Wall Functions L ude 5c sibuct fee Options C viscous Heating Figure 6 2 34 The Viscous Model Dialog Box Next select the function name e g udf sct libudf from the Turbulent Schmidt Number drop
433. inter to structure that stores the dynamic mesh attributes that you have specified or that are calculated by ANSYS FLUENT real time Current time real dtime Time step Function returns void There are four arguments to DEFINE SDOF PROPERTIES name properties dt and dtime You provide the name of the UDF properties dt and dtime are variables that are passed by the ANSYS FLUENT solver to your UDF The property array pointer that is passed to your function allows you to specify values for any of the following SDOF properties SDOF_MASS mass SDOF_IXX moment of inertia SDOF_IYY moment of inertia SDOF_IZZ moment of inertia SDOF_IXY product of inertia SDOF_IXZ product of inertia SDOF_IYZ product of inertia SDOF_LOAD_LOCAL boolean SDOF_LOAD_F_X external force Release 12 0 ANSYS Inc January 26 2009 2 221 DEFINE Macros SDOF_LOAD_F_Y external force SDOF_LOAD_F_Z external force SDOF_LOAD_M_X external moment SDOF_LOAD_M_Y external moment SDOF_LOAD_M_Z external moment The boolean prop SDOF_LOAD_LOCAL can be used to determine whether the forces and moments are expressed in terms of global coordinates FALSE or body coordinates TRUE The default value for prop SDOF_LOAD_LOCAL is FALSE Custom Transformation Variables The default transformations used by ANSYS FLUENT are typical for most aerospace and other types of appli
434. ion dialog box e g the Wall dialog box as shown in Figure 6 4 1 Release 12 0 ANSYS Inc January 26 2009 6 63 Hooking UDFs to ANSYS FLUENT Zone Name Phase wall bottom mixture Adjacent Cell Zone Fluid Momentum Thermal Radiation Species DPM Multiphase UDS Discrete Phase Model Conditions Boundary Cond Type user defined v Boundary Cond Function bc_reflect libudf J Figure 6 4 1 The Wall Dialog Box Click the DPM tab and select user_defined from the Boundary Cond Type drop down list in the Discrete Phase Model Conditions group box This will expand the dialog box to allow you to select the function name e g bc_reflect libudf from the Boundary Cond Function drop down list Figure 6 4 1 Click OK See Section 2 5 1 DEFINE_DPM_BC for details about DEFINE_DPM_BC functions 6 64 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 2 Hooking DEFINE_DPM_BODY_FORCE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_BODY_FORCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model dialog box Figure 6 4 2 in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box Vere beeen Edit Discrete Phase Model
435. ion s you wish to hook to your model from the Available Initialization Functions list Click Add and then OK to close the dialog box The name of the function you selected will be displayed in the Initialization field of the User Defined Function Hooks dialog box If you select more than one function the number will be displayed e g 2 selected Click OK in the User Defined Function Hooks dialog box to apply the settings See Section 2 2 8 DEFINE_INIT for details about defining DEFINE_INIT functions 6 1 6 Hooking DEFINE ON DEMAND UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_ON_DEMAND UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Execute On Demand dialog box Figure 6 1 10 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT open the Execute On Demand dialog box Define User Defined Execute On Demand Execute on Demand Execute on Demand on_demand_calc libudf v Figure 6 1 10 The Execute On Demand Dialog Box 6 10 Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking General Purpose UDFs Select the function name e g on_demand_calc libudf in the Execute On Demand drop down list and click Execute ANSYS FLUENT will execute the UDF immediately Click Close to close the dialog box See Section 2 2 9 DEFINE ON DEMAND for details about defining DEF
436. itude temperature pressure user defined scalar boundary value discrete phase boundary condition DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEF INE_PROFILE secondary phase s phase dependent primary and secondary phases s primary and secondary phases s primary and secondary phases s mixture mixture mixture Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source species source user defined scalar source turbulence dissipation rate turbulence kinetic energy DEF INE_SOURCE DEF INE_SOURCE DEF INE_SOURCE DEF INE_SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE PROFILE DEFINE_PROFILE primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s primary and secondary phase s phase dependent mixture primary and secondary phase s primary and secondary phase s Release 12 0 ANSYS Inc January 26 2009 Quick Reference Guide for Multiphase DEFINE Macros Table C 5 2 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Fluid velocity DEFINE_PROFILE primary and secondary phase s temperature DEFINE PROFILE primary and species mass fraction porosity viscous resistance inertial r
437. ives for parallel UDFs because all of these macros automatically do the following e send the variable value if compiled as the host version e receive and then set the local variable if compiled as a compute node version e do nothing in the serial version The most common use for this set of macros is to pass parameters or boundary conditions from the host to the nodes processes See the example UDF in Section 7 8 Parallel UDF Example for a demonstration of usage Release 12 0 ANSYS Inc January 26 2009 7 15 Parallel Considerations Node to Host Data Transfer To send data from compute node 0 to the host process we use macros of the form node_to_host_type_num val_1 val_2 val_num where num is the number of variables that will be passed in the argument list and type is the data type of the variables that will be passed The maximum number of variables that can be passed is 7 Arrays and strings can also be passed from host to nodes one at a time as shown in the examples below Note that unlike the host_to_node macros which pass data from the host process to all of the compute nodes indirectly via compute node 0 node_to_host macros pass data only from compute node 0 to the host Examples integer and real variables passed from compute node 0 to host node_to_host_int_1 count node_to_host_real_7 leni len2 width1 width2 breadthi breadth2 vol string and array variables passed from compu
438. ixture_thread second_column_phase_index first_column_phase_index real name cell_t c Thread mixture_thread int second_column_phase_index int first_column_phase_index define DEFINE_HET_RXN_RATE name c t hr mw yi rr rr_t void name cell_t c Thread t Hetero_Reaction hr real mw MAX_PHASES MAX_SPE_EQNS B 4 Release 12 0 ANSYS Inc January 26 2009 B 4 Dynamic Mesh Model DEFINE Macros real yi MAX_PHASES MAX_SPE_EQNS real rr real rr_t define DEFINE_MASS_TRANSFER name c mixture_thread from_phase_index from_species_index to_phase_index to_species_index real name cell_t c Thread mixture_thread int from_phase_index int from_species_index int to_phase_index int to_species_index define DEFINE_VECTOR_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index vector_result void name cell_t c Thread mixture_thread int second_column_phase_index int first_column_phase_index real vector_result B 4 Dynamic Mesh Model DEFINE Macros The following definitions for dynamic mesh model DEFINE macros see Section 2 6 Dy namic Mesh DEFINE Macros are taken from the udf h header file define DEFINE_CG_MOTION name dt vel omega time dtime void name Dynamic_Thread dt real vel real omega real time real dtime define DEFINE_DYNAMIC_ZONE_PROPERTY name dt swirl_center void name Dynamic_Thread dt real swirl_cen
439. jacent compute node Figure 7 1 2 This duplication of cells at a partition boundary becomes important when you want to loop over cells in a parallel mesh There are separate macros for looping over interior cells exterior cells and all cells See Section 7 5 5 Looping Macros for details Interior cells Exterior cell Figure 7 2 1 Partitioned Mesh Cells Faces at Partition Boundaries There are three classifications of faces in a partitioned mesh interior boundary zone and external Figure 7 2 2 Interior faces have two neighboring cells Interior faces that lie on a partition boundary are referred to as partition boundary faces Boundary zone Release 12 0 ANSYS Inc January 26 2009 7 7 Parallel Considerations faces lie on a physical mesh boundary and have only one adjacent cell neighbor External faces are non partition boundary faces that belong to exterior cells External faces are generally not used in parallel UDFs and therefore will not be discussed here Boundary zone face Interior face Partition boundary face External face Interior face Figure 7 2 2 Partitioned Mesh Faces Note that each partition boundary face is duplicated on adjacent compute nodes Fig ure 7 1 2 This is necessary so that each compute node can calculate its own face values However this duplication can result in face data being counted twice when UDFs are involved in operations that involve summing data in a thr
440. k UDF for initializing phase volume fraction BE AAR I I I AGRA I I A A kK OKI AK KEK A ACA A A KK KK kkk kk aK kkk include udf h domain pointer that is passed by INIT function is mixture domain DEFINE_INIT my_init_function mixture_domain int phase_domain_index cell_t cell Thread cell_thread Domain subdomain real xc ND_ND loop over all subdomains phases in the superdomain mixture sub_domain_loop subdomain mixture_domain phase_domain_index loop if secondary phase if DOMAIN_ID subdomain 3 loop over all cell threads in the secondary phase domain thread_loop_c cell_thread subdomain loop over all cells in secondary phase cell threads begin_c_loop_all cell cell_thread C_CENTROID xc cell cell_thread if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 set volume fraction to 1 for centroid C_VOF cell cell_thread 1 else otherwise initialize to zero C_VOF cell cell_thread 0 end_c_loop_all cell cell_thread Release 12 0 ANSYS Inc January 26 2009 3 61 Additional Macros for Writing UDFs Looping Over Phase Threads in Mixture sub_thread_loop The sub_thread_loop macro loops over all phase level threads subthreads associated with a mixture level thread The macro steps through and returns the pointer to each subthread as well as the corresponding phase_domain_index As discusse
441. k OK in the Mass sources dialog box to accept the new boundary condition The source term text box in the cell zone condition dialog box will display the number of sources e g 2 sources Click OK to close the cell zone condition dialog box and fix the new mass source terms for the solution calculation Repeat this step for all of the source terms you wish to customize using a UDF See Section 2 3 19 DEFINE SOURCE for details about DEFINE SOURCE functions Release 12 0 ANSYS Inc January 26 2009 6 43 Hooking UDFs to ANSYS FLUENT Mass kg m3 s sources Number of Mass kgj m3 s sources 2 a i ud usr_mass_src1 libudf v 2 z fudF usr_mass_src2 sibudf x Figure 6 2 27 The Mass sources Dialog Box 6 2 20 Hooking DEFINE_SOX_RATE UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE_SOX_RATE UDF in ANSYS FLUENT the function name you supplied in the DEFINE macro argument e g user_sox libudf will become visible and selectable for the SOx Rate drop down list in the SOx Model dialog box Figure 6 2 28 ena E 10a v Edit By default the custom SO rate of your UDF is added to the rate calculated internally by ANSYS FLUENT The UDF rate will be added to the forward rate if it is assigned to the POLLUT_FRATE macro or the reverse rate if it is assigned to the POLLUT_RRATE macro If you would rather entirely replace the internally calculated SO rate with your
442. king DEFINE_SOLAR_INTENSITY UDFs 6 40 6 2 19 Hooking DEFINE SOURCE UDES s s sse d 6 Re dae woh as 6 42 6 2 20 Hooking DEFINE SOX RATE UDFs aaa aaa ewe 6 44 6 2 21 Hooking DEFINE_SPECIFIC HEAT UDFs aaa aaa a aaa 6 46 6 2 22 Hooking DEFINE SR RATE UDFs lt lt s 2 4 4 4 na Nae 4 6 47 6 2 29 Hooking DEFINE TRANS UDNS 5 44 lt s miia lt lt 0 4 4 lt 6 49 6 2 24 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs 6 50 6 2 25 Hooking DEFINE_TURB_SCHMIDT UDFs 6 51 6 2 26 Hooking DEFINE_TURBULENT_VISCOSITY UDFs 6 52 6 2 27 Hooking DEFINE_VA RATE UDFs 22 54 52 be ee ee ee 6 53 6 2 28 Hooking DEFINE WALL_FUNCTIONS UDFs 6 54 6 3 Hooking Mu ukiphase UDF S 2246 eee ee eee ORES eee eo 6 55 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs 6 55 6 3 2 Hooking DEFINE EXCHANGE_PROPERTY UDFs 6 57 6 3 3 Hooking DEFINE_HET_RXN_RATE UDFs 6 59 6 3 4 Hooking DEFINE_MASS_TRANSFER UDFs 6 60 6 3 5 Hooking DEFINE_VECTOR_EXCHANGE_PROPERTY UDFs 6 61 6 4 Hooking Discrete Phase Model DPM UDFs 6 63 6 4 1 Hooking DEFINE DPM_BC UDFs 2 4 e8 4 4a eek oe es 6 63 6 4 2 Hooking DEFINE_DPM_BODY_FORCE UDFs 6 65 Release 12 0 ANSYS Inc January 26 2009 Vil CONTENTS viii 64 5 Hooking DEFINE DPMORAG UDES e cr misa di mist anu poe wh 6 66 6 4 4 Hooking DEFINE DPM_EROSION UDFs 6
443. king to ANSYS FLUENT 6 78 DEFINE_DPM_TIMESTEP UDF s defining 2 202 hooking to ANSYS FLUENT 6 79 DEFINE_DPM_VP_EQUILIB UDFs defining 2 205 hooking to ANSYS FLUENT 6 80 DEFINE DYNAMIC ZONE PROPERTY UDF s defining 2 211 hooking to ANSYS FLUENT 6 82 DEFINE EMISSIVITY WEIGHTING FACTOR UDFs defining 2 41 hooking to ANSYS FLUENT 6 22 DEF INE_EXCHANGE_PROPERTY UDF defining 2 139 hooking to ANSYS FLUENT 6 57 DEF INE_EXECUTE_AFTER_CASE UDF s defining 2 16 DEFINE EXECUTE AFTER DATA UDF s defining 2 16 DEFINE EXECUTE AT END UDFs defining 2 8 hooking to ANSYS FLUENT 6 5 DEFINE EXECUTE AT EXIT UDFs defining 2 10 hooking to ANSYS FLUENT 6 6 DEFINE EXECUTE FROM GUI UDFs defining 2 11 DEFINE EXECUTE ON LOADING UDF s defining 2 13 DEFINE_GEOM UDFs defining 2 216 hooking to ANSYS FLUENT 6 85 DEFINE_GRAY_BAND_ABS_COEFF UDFs defining 2 43 hooking to ANSYS FLUENT 6 23 Release 12 0 ANSYS Inc January 26 2009 Index DEFINE_GRID_MOTION UDFs defining 2 218 hooking to ANSYS FLUENT 6 87 DEFINE_HEAT_FLUX UDFs defining 2 45 example 8 45 hooking to ANSYS FLUENT 6 24 DEFINE_HET_RXN_RATE UDFs defining 2 144 hooking to ANSYS FLUENT 6 59 DEFINE_IGNITE_SOURCE UDF s defining 2 47 hooking to ANSYS FLUENT 6 25 DEFINE_INIT UDFs defining 2 18 hooking to ANSYS FLUENT 6 9 DEFINE_MASS_TRANSFER UDF s defining 2 149 hooking to ANSYS FLUENT 6 60 DEFINE_NET_REACTION_RATE UDF s defining 2 50 hooking t
444. l DPM UDFs The DPM model can be used for the following parallel options e Shared Memory e Message Passing When you are using a DPM specific UDF see Section 2 5 Discrete Phase Model DPM DEFINE Macros it will be executed on the machine that is in charge of the considered particle based on the above mentioned parallel options Since all fluid variables needed for DPM models are held in data structures of the tracked particles no special care is needed when using DPM UDFs in parallel ANSYS FLUENT with the exception of when you are writing in parallel to a sampling output file In this case you are not allowed to use the C function fprintf Instead new functions are provided to enable the parallel file writing Each node writes its information to separate files which are put together and sorted upon closure of the file by ANSYS FLUENT The new functions can be used with the same parameter lists as the C function fprintf The sorting of the files in parallel requires the specification of an extended parameter list Information can be placed at the top of the file that will not sorted by using the function par_fprintf_head par_fprintf_head x coordinate y coordinate z coordinate n This function will place the string x coordinate y coordinate z coordinate at the top of the file Information is put on the nodes using the function par_fprintf par_fprintf d d he e Ze n P_INJ_ID P_INJECTION p p gt part_id P_POS p 0 P_
445. l Interaction Particle Treatment Interaction with Continuous Phase _ Unsteady Particle Tracking C Update DPM Sources Every Flow Iteration Number of Continuous Phase 10 ia Iterations per DPM Iteration iv Tracking Physical Models UDF Numerics Parallel User Defined Functions User Yariables Body Force none w Number of Scalars 0 al wv Erosion Accretion grme a Scalar Update pone Source none DPM Time Step none Figure 6 4 4 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next enable the Interaction with Continuous Phase option under Interaction in the Dis crete Phase Model dialog box Then click the Physical Models tab and enable the Ero sion Accretion option Finally click the UDF tab and select the function name e g dpm accr libudf from the Erosion Accretion drop down list in the User Defined Functions group box Figure 6 4 3 and click OK See Section 2 5 4 DEFINE_DPM_EROSION for details about DEFINE_DPM_EROSION functions Release 12 0 ANSYS Inc January 26 2009 6 67 Hooking UDFs to ANSYS FLUENT 6 4 5 Hooking DEFINE_DPM_HEAT_MASS UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_HEAT_MASS UDF the name of the function you supplied as a DEFINE macro arg
446. l Macros for Writing UDFs Cell cl Cell or Face Centroid A Nodes Face f Cell c0 b pg Figure 3 2 2 Adjacent Cells c0 and cl with Vector and Gradient Definitions Adjacent Cell Index F_CO F_C1 The cells on either side of a face may or may not belong to the same cell thread Referring to Figure 3 2 2 if a face is on the boundary of a domain then only cO exists c1 is undefined for an external face Alternatively if the face is in the interior of the domain then both cO and c1 exist There are two macros F_CO f t and F_C1 f t that can be used to identify cells that are adjacent to a given face thread t F_CO expands to a function that returns the index of a face s neighboring cO cell Figure 3 2 2 while F_C1 returns the cell index for c1 Figure 3 2 2 if it exists Table 3 2 24 Adjacent Cell Index Macros Defined in mem h Macro Argument Types Returns F_CO f t face_t f Thread t cell_t c for cell c0 F_Ci f t face_t f Thread t cell_t c for cell cl See Section 2 7 3 DEFINE_UDS_FLUX for an example UDF that utilizes F_CO 3 26 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Adjacent Cell Thread THREAD_TO THREAD_T1 The cells on either side of a face may or may not belong to the same cell thread Referring to Figure 3 2 2 if a face is on the boundary of a domain then only cO exists c1 is undefined for an external face Alternatively
447. l dialog box in ANSYS FLUENT See Section 6 4 10 Hooking DEFINE DPM SCALAR UPDATE UDFs for details on how to hook your DEFINE_DPM_SCALAR_UPDATE UDF to ANSYS FLUENT 2 1 92 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 11 DEFINE_DPM_SOURCE Description You can use DEFINE_DPM_SOURCE to specify particle source terms The function allows access to the accumulated source terms for a particle in a given cell before they are added to the mass momentum and energy exchange terms for coupled DPM calculations Usage DEFINE DPM SOURCE name c t S strength p Argument Type Description symbol name UDF name cellt c Index that identifies the cell that the particle is currently in Thread t Pointer to the thread the particle is currently in dpms_t S Pointer to the source structure dpms_t which contains the source terms for the cell real strength Particle number flow rate in particles second divided by the number of tries if stochastic tracking is used Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked Function returns void There are six arguments to DEFINE DPM SOURCE name c t S strength and p You supply name the name of the UDF c t S strength and p are variables that are passed by the ANSYS FLUENT solver to your UDF The modified source terms after they have been computed by the function
448. l sum_diss 0 cell_t c d Get_Domain 1 mixture domain if multiphase thread_loop_c t d Release 12 0 ANSYS Inc January 26 2009 2 9 DEFINE Macros if FLUID_THREAD_P t begin_c_loop c t sum_diss C_D c t C_VOLUME c t end_c_loop c t printf Volume integral of turbulent dissipation g n sum_diss fflush stdout Hooking an Execute at End UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_EXECUTE_AT_END is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g execute_at_end will become visible and selectable via the User Defined Function Hooks dialog box in AN SYS FLUENT Note that you can hook multiple end iteration functions to your model See Section 6 1 3 Hooking DEFINE_EXECUTE_AT_END UDF for details 2 2 4 DEFINE_EXECUTE_AT_EXIT Description DEF INE_EXECUTE_AT_EXIT is a general purpose macro that can be used to execute a func tion at the end of an ANSYS FLUENT session Usage DEF INE_EXECUTE_AT_EXIT name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE EXECUTE AT EXIT name You supply name the name of the UDF 2 10 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Hooking an Execute at Exit UDF to ANSYS FLUENT After the UDF th
449. le Follow the instructions below in Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box After it has been interpreted the UDF function name s that you supplied in the DEFINE macro s will appear in drop down lists in graphical dialog boxes in ANSYS FLUENT ready for you to hook to your CFD model Alternatively if you wish to compile your UDF source file see Chapter 5 Compiling UDFs for details e Section 4 1 Introduction e Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box e Section 4 3 Common Errors Made While Interpreting A Source File 4 1 Introduction An interpreted UDF is a function that is interpreted directly from a source file e g udfexample c at runtime You will use the Interpreted UDFs dialog box to interpret all of the functions in a source file e g udfexample c in a single step After a source file is interpreted you can write the case file and the names and contents of the interpreted function s will be stored in the case In this way the function s will be automatically interpreted whenever the case file is subsequently read After it has been interpreted either manually through the Interpreted UDFs dialog box or automatically upon reading a case file all of the interpreted UDFs that are contained within a source file will become visible and selectable in graphical user interface dialog boxes in ANSYS FLUENT Inside ANSYS FLUENT the source code is c
450. le if your multiphase UDF defines a custom profile for a particular boundary zone using DEFINE PROFILE and is hooked to the appropriate phase or mixture in ANSYS FLUENT in the relevant boundary condition dialog box then appropriate phase or mixture variables will be passed to your function by the solver at run time There may however be more complex functions you wish to write that require a variable that is not directly passed through its arguments DEFINE_ADJUST and DEFINE_INIT functions for example are passed mixture domain variables only If a UDF requires a phase domain pointer instead then it will need to utilize macros presented in this section to retrieve it ON DEMAND UDFS aren t directly passed any variables through their arguments Consequently any on demand function that requires access to phase or domain variables will also need to utilize macros presented in this section to retrieve them Recall that when you are writing UDFs for multiphase models you will need to keep in mind the hierarchy of structures within ANSYS FLUENT see Section 1 10 1 Multiphase specific Data Types for details The particular domain or thread structure that gets passed into your UDF from the solver depends on the DEFINE macro you are using as well as the domain the function is hooked to either through the graphical user interface or hardwired in the code As mentioned above it also may depend on the multiphase model that you are using Refer t
451. le equilibrium vapor pressure 2 205 particle initialization 2 177 particle laws 2 181 property 2 186 scalar update 2 189 source term 2 193 spray collide 2 194 dispersed phase properties 2 186 DO model UDFs diffuse reflectivity 2 36 emissivity weighting factor 2 41 gray band coefficient 2 43 non gray emissivity weighting factor 2 41 gray band coefficient 2 43 scattering phase 2 95 source terms 2 38 specular reflectivity 2 39 Domain data structure 1 10 domain ID 3 68 domain pointer 1 11 DOMAIN_ID 3 60 3 68 domain_id 1 18 3 31 DOMAIN SUB_DOMAIN 3 65 3 66 DOMAIN_SUPER_DOMAIN 3 67 domains 1 10 interaction 1 17 mixture 1 17 phase 1 17 referencing 1 17 subdomains 1 17 superdomains 1 17 dot product 3 73 Release 12 0 ANSYS Inc January 26 2009 Index DPM DEFINE macros quick reference guide 2 154 DPM macros particle cell index thread pointer 3 37 particle material properties 3 37 particle species laws and user scalars 3 37 particles at current position 3 36 particles at entry to cell 3 37 particles at injection into domain 3 37 DPM property UDFs 2 186 DPM UDFs body force 2 163 boundary condition 2 156 drag coefficient 2 165 erosion and accretion rates 2 167 heat and mass transfer 2 173 particle initialization 2 177 particle laws 2 181 property 2 186 scalar update 2 189 source term 2 193 spray collide 2 194 switching custom laws 2 196 DPM
452. le name For example to access the user defined Scheme variable pres_av thread id in your UDF C function you will use RP_LGet_Integer You can then assign the variable returned to a local variable you have declared in your UDF e g surface _thread_id as demonstrated below surface_thread_id RP_Get_Integer pres_av thread id 3 78 Release 12 0 ANSYS Inc January 26 2009 3 7 Input Output Macros 3 7 Input Output Macros ANSYS FLUENT provides some utilities in addition to the standard C I O functions that you can use to perform input output I O tasks These are listed below and are described in the following sections Message format prints a message to the console Error format prints an error message to the console Message The Message macro is a utility that displays data to the console in a format that you specify int Message char format The first argument in the Message macro is the format string It specifies how the remaining arguments are to be displayed in the console The format string is defined within quotes The value of the replacement variables that follow the format string will be substituted in the display for all instances of type The character is used to designate the character type Some common format characters are 4d for integers f for floating point numbers g for double data type and e for floating point numbers in exponential format with e before the exponent C
453. led object file s that you want to build a shared library for e g myobject1 o Use a space delimiter to specify multiple object files e g myobjecti o myobject2 0 An excerpt from a sample makefile is shown below Hom sn makefile for user defined functions Hom ssn Hom sn User modifiable section Ho ss SOURCES udf_sourcel c FLUENT_INC path ansys_inc v120 fluent Precompiled User Object files for example o files from f sources USER_OBJECTS myobjectl o myobject2 0 Release 12 0 ANSYS Inc January 26 2009 5 19 Compiling UDFs Ce Build targets do not modify below this line e SSS Se SS SS se SS Ss SSeS SSS a SaaS SSeS ees eee Note that in the previous example path represents the directory where you installed ANSYS FLUENT 4 In your library directory e g libudf execute the Makefile by typing a command that begins with make and includes the architecture of the machine on which you will run ANSYS FLUENT which you identified in a previous step e g ultra make FLUENT_ARCH ultra The following messages will be displayed linking to src makefile in ultra 2d building library in ultra 2d linking to src makefile in ultra 3d building library in ultra 3d 5 4 1 Example Link Precompiled Objects to ANSYS FLUENT The following example demonstrates the linking of a FORTRAN object file test o to ANSYS FLUENT for use in a UDF named test_use c This partic
454. les 5 9 compiler directives 1 5 about 7 12 example 7 13 compiling source files procedure 5 5 using GUI 5 5 compiling UDF source files 5 1 compute nodes 7 4 connectivity macros 3 5 3 7 control statements A 10 cphi UDFs 2 33 cpp 4 4 8 7 CPP Command Name 4 4 8 7 Create Edit Materials dialog box 6 23 6 36 6 39 6 46 6 73 8 32 critical momentum thickness Reynolds number UDFs 2 119 cross product 3 73 CURRENT_TIME 2 7 3 75 8 19 CURRENT_TIMESTEP 3 75 Custom Laws dialog box 6 71 6 78 data file functions reading and writing 2 23 data structure pointers 1 11 data structures thread 1 9 data types about 1 10 case sensitive 1 11 cell index 1 10 Domain 1 10 face index 1 10 node 1 10 Release 12 0 ANSYS Inc January 26 2009 thread 1 10 user defined A 7 Data_Valid_P 2 6 2 210 3 80 debugging your UDF 4 5 DEFINE macros 1 2 1 4 2 1 compilation error 1 4 DPM 2 154 dynamic mesh 2 208 format 1 4 general solver 2 2 model specific 2 25 multiphase 1 17 2 135 Eulerian model C 5 C 8 C 10 C 13 Mixture model C 3 VOF model C 1 define A 17 DEFINE_ADJUST UDFs defining 2 4 example 8 45 hooking to ANSYS FLUENT 6 2 DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs defining 2 227 hooking to ANSYS FLUENT 6 90 DEFINE_CAVITATION_RATE UDFs defining 2 137 hooking to ANSYS FLUENT 6 55 DEFINE_CG_MOTION UDFs defining 2 209 hooking to ANSYS FLUENT 6 81 DEFINE_CHEM_STEP UDFs defining
455. les and fluid erosion and accretion rates heat and mass transfer of multicomponent particles to the gas phase initializes injections custom laws for particles modifies what is written to the sampling plane output material properties updates scalar every time a particle position is updated particle source terms particle collisions algorithm changes the criteria for switching between laws time step control for DPM simulation equilibrium vapor pressure of vaporizing components of multicomponent particles DEF INE_DPM_BC DEFINE_DPM_BODY_ FORCE DEFINE_DPM_DRAG DEFINE_DPM_EROSION DEFINE_DPM_HEAT_MASS DEF INE_DPM_INJECTION_INIT DEF INE_DPM_LAW DEFINE_DPM_OUTPUT DEFINE _DPM_PROPERTY DEF INE_DPM_SCALAR_UPDATE DEFINE_DPM_SOURCE DEF INE_DPM_SPRAY_COLLIDE DEFINE DPM SWITCH DEFINE_DPM_TIMESTEP DEFINE_DPM_VP_EQUILIB boundary condition e g Velocity Inlet Discrete Phase Model Discrete Phase Model Discrete Phase Model Set Injection Properties Set Injection Properties Custom Laws Sample Trajectories Create Edit Materials Discrete Phase Model Discrete Phase Model Discrete Phase Model Custom Laws Discrete Phase Model Create Edit Materials Release 12 0 ANSYS Inc January 26 2009 2 155 DEFINE Macros 2 5 1 DEFINE_DPM_BC Description You can use DEFINE_DPM_BC to specify your own boundary conditions for particles The function is executed every time a particle touches a boun
456. libudf from the Output drop down list under User Defined Functions Then click Compute for steady calculations or Start for transient calculations See Section 2 5 8 DEFINE_DPM_OUTPUT for details about DEFINE_DPM_OUTPUT functions 6 72 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 9 Hooking DEFINE_DPM_PROPERTY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_PROPERTY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Functions dialog box To hook the UDF to ANSYS FLUENT you will first need to open the Materials task page 4 BV ElecaelS Select a material from Materials list and click the Create Edit button to open the Create Edit Materials dialog box Figure 6 4 9 Create Edit Materials Name Material Type inert particle anthracite Order Materials by J Name Chemical Formula FLUENT Inert Particle Materials anthracite O Chemical Formula Pr FLUENT Database Properties Cp Specific Heat j kg k er 1680 Thermal Conductivity vwim k eae 0 33 Particle Emissivity eRe coal_emissivity libudf Particle Scattering Factor constant User Defined Database Figure 6 4 9 The Create Edit Materials Dialog Box
457. licking the Create Edit button Resin Tee Create Edit Create Edit Materials Name Material Type Order Materials by liquid_metal Fluid v Name O Chemical Formula Sranie FLUENT Fluid Materials a liquid_metal v FLUENT Database 1 User Defined Database Properties Density kg m3 an 8000 Cp Specific Heat j kg k ndak 680 Thermal Conductivity wim k eee 30 Viscosity kg itr s M o defined cell_viscosity v Figure 8 2 18 The Create Edit Materials Dialog Box In the Create Edit Materials dialog box select user defined in the drop down list for Viscos ity This will open the User Defined Functions dialog box Figure 8 2 19 from which you can select the appropriate function name In this example only one option is available but in other examples you may have several functions from which to choose Recall that if you need to compile more than one interpreted UDF the functions can be concatenated in a single source file prior to compiling 8 32 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples User Defined Fu cell viscosity Figure 8 2 19 The User Defined Functions Dialog Box The results of this model are similar to those obtained in Section 8 2 2 Adding a Mo mentum Source to a Duct Flow Figure 8 2 20 shows the viscosity field resulting from the
458. lied as a DEFINE macro argument will become visible and selectable in the In Cylinder Output Controls dialog box Figure 6 5 2 6 82 Release 12 0 ANSYS Inc January 26 2009 6 5 Hooking Dynamic Mesh UDFs To hook the UDF to ANSYS FLUENT you will first need to select Transient from the Time list in the Solver group box of the General task page lt Tee Transient Next enable the Dynamic Mesh option in the Dynamic Mesh task page Duele Dynamic Mesh Then enable the In Cylinder option in the Options group box and click the Settings button to open the In Cylinder Settings dialog box After you have updated the parameters in this dialog box click the Output Controls button to open the In Cylinder Output Controls dialog box Figure 6 5 2 In Cylinder Output Controls In Cylinder Data Write Frequency 0 i Swirl Center Method Cell Zones swirl_udf libudf Flcylinder Swirl Axis Tumble Axis Tumble Axis all File Name in cylinder ic swirl txt Figure 6 5 2 In Cylinder Output Controls Dialog Box Select the UDF library e g swirl_udf libudf from the Swirl Center Method drop down list in the In Cylinder Output Controls dialog box Click OK and close the In Cylinder Output Controls dialog box See Section 2 6 2 DEFINE_DYNAMIC_ZONE_PROPERTY for further details about DEFINE_DYNAMIC_ZONE_PROPERTY func
459. ll become visible and selectable in the Discrete Phase Model dialog box Figure 6 4 11 in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box Vere beeen Edit Discrete Phase Model Interaction Particle Treatment C Interaction with Continuous Phase _ Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel User Defined Functions User Variables Body Force Number of Scalars a none 0 i Scalar Update mrupa Source none DPM Time Step none Figure 6 4 11 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the UDF tab in the Discrete Phase Model dialog box Select the function name e g melting_index libudf from the Scalar Update drop down list under User Defined Functions Figure 6 4 11 and click OK See Section 2 0 10 DEFINE DPM SCALAR UPDATE for details about DEFINE_DPM_SCALAR_UPDATE functions 6 75 Release 12 0 ANSYS Inc January 26 2009 Hooking UDFs to ANSYS FLUENT 6 4 11 Hooking DEFINE_DPM_SOURCE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SOURCE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model dialog box
460. ls 2 4 2 DEFINE EXCHANGE PROPERTY Description You can use DEFINE_EXCHANGE_PROPERTY to specify UDFs for some phase interaction variables in multiphase models These include net heat transfer rates between phases and drag and lift coefficient functions Below is a list of user defined functions that can be specified using DEFINE EXCHANGE PROPERTY for the multiphase models in AN SYS FLUENT Note that there are some phase interaction variables such as vaporization pressure and surface tension coefficient cavitation parameters that are defined using DEFINE_PROPERTY See Section 2 3 16 DEFINE_PROPERTY UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 1 39 DEFINE Macros Table 2 4 2 DEFINE_ EXCHANGE_PROPERTY Variables Mixture Model Eulerian Model net heat transfer rate drag exchange coefficient drag coefficient lift coefficient Usage DEF INE_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index first_column_phase_index Note that all of the arguments to a DEFINE macro must be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name cell_t c Cell index Thread mixture_thread Pointer to the mixture level thread int second column phase index Identifier that corresponds to the pair of phases in your multiphase flow that you are specifying a slip velocity f
461. lue DEFINE_PROFILE mixture discrete phase boundary condition DEFINE_PROFILE mixture Release 12 0 ANSYS Inc January 26 2009 C 3 Quick Reference Guide for Multiphase DEFINE Macros Table C 2 2 DEFINE Macro Usage for the Mixture Model Variable Macro Phase Specified On Fluid mass source momentum source energy source turbulence kinetic energy source turbulence dissipation rate source granular temperature source user scalar source species source species mass fractions velocity temperature turbulence kinetic energy turbulence dissipation rate porosity granular temperature viscous resistance inertial resistance DEFINE SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE SOURCE DEFINE SOURCE DEF INE_SOURCE DEFINE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE PROFILE primary and secondary phase s mixture mixture mixture mixture secondary phase s mixture phase dependent phase dependent mixture mixture mixture mixture mixture secondary phase s primary and secondary phase s primary and secondary phase s Wall roughness height roughness constant internal emissivity shear stress components moving velocity components heat flux heat generation rate heat transfer coefficient external emissivity external radiation temperature free stream tem
462. lues that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next ANSYS FLUENT solves the governing equations of continuity and momentum in a coupled fash ion which is simultaneously as a set or vector of equations Energy species transport turbulence and other transport equations as required are subsequently solved sequen tially and the remaining process is the same as the pressure based segregated solver Density Based Solver As is the case for the other solvers the solution process for the density based solver Figure 1 9 3 begins with a two step initialization sequence that is executed outside the solution iteration loop This sequence begins by initializing equations to user entered or default values taken from the ANSYS FLUENT user interface Next PROFILE UDF s are called followed by a call to INIT UDFs Initialization UDFs overwrite initialization values that were previously set The solution iteration loop begins with the execution of ADJUST UDFs Next ANSYS FLUENT solves the governing equations of continuity and momentum energy and species transport in a coupled fashion which is simultaneously as a set or vector of equations Turbulence and other transport equations as required are subsequently solved sequen tially and the remaining process is the same as the pressure based segregated solver Release 12 0 ANSYS Inc January 26 2009 1 13 Overview User Defined Pro
463. lver to your UDF Example The following UDF named my_init_func initializes flow field variables in a solution It is executed once at the beginning of the solution process The function can be executed as an interpreted or compiled UDF in ANSYS FLUENT POR CC AO kkk kkk kkk kk kkk kkk kk kkk kk kkk kkk kkk kk kk kkk k k kk k UDF for initializing flow field variables EEEE EEEE ooo ooo o kkk k kkk kkk kkk include udf h DEFINE_INIT my_init_func d 2 18 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros cell_t c Thread t real xc ND_ND loop over all cell threads in the domain thread_loop_c t d loop over all cells begin_c_loop_all c t C_CENTROID xc c t if sqrt ND_SUM pow xc 0 0 5 2 pow xc 1 0 5 2 pow xc 2 0 5 2 lt 0 25 C_T c t 400 else C_T c t 300 end_c_loop_all c t The macro ND_SUM a b c computes the sum of the first two arguments 2D or all three arguments 3D It is useful for writing functions involving vector operations so that the same function can be used for 2D and 3D For a 2D case the third argument is ignored See Chapter 3 Additional Macros for Writing UDFs for a description of predefined macros such as C_CENTROID and ND_SUM Hooking an Initialization UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_INIT is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Com
464. m T gt 288 K fluid has a molecular value for the liquid 5 5 x 10 kg m s while the viscosity for the cooler region T lt 286 K has a much larger value 1 0 kg m s In the intermediate temperature range 286 K lt T lt 288 K the viscosity follows a linear profile that extends between the two values given above u 143 2135 0 497257 2 3 8 This model is based on the assumption that as the liquid cools and rapidly becomes more viscous its velocity will decrease thereby simulating solidification Here no correction is made for the energy field to include the latent heat of freezing The source code can be interpreted or compiled in ANSYS FLUENT J EK K K K K K 2k k 2k 3k ak ak ak ak 3k aK 2K aK 2K 2 2K 2K aK aK aK K K K 2K K 2K 3K 3K 2K 3K 3K 3K 3K 3K 2K 3K 2K aK 2 2K 2K I I 3K 2K 3K A A A ACA K KKK K K UDF that simulates solidification by specifying a temperature dependent viscosity property KK k ak ak ak ak K K aK K K 2K 3K 3K 2K 3K 3K 3K 3K 3K 3K 3K 2K I I I K A A A A A A A 3K 3K 3K 35 2K 2K 2 21 21 21 21 21 21 K K K 2K 3K 2K KK K 2k 2k 2k 2k include udf h DEFINE_PROPERTY cell_viscosity c t real mu_lam real temp C_T c t if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam The function cell_viscosity is defined on a cell Two real variables are introduced temp the value of C_T c t and mu_lam the laminar vis
465. m equal to the negative of that used in the incident radiation equation and the DEFINE_HEAT_FLUX UDF is used to alter the boundary conditions at the walls for the energy equation In the solver at least one user defined scalar UDS equation must be enabled The scalar diffusivity is assigned in the Create Edit Materials dialog box for the scalar equation The scalar source and energy source terms are assigned in the boundary condition dialog box for the fluid zones The boundary condition for the scalar equation at the walls is assigned in the boundary condition dialog box for the wall zones The DEFINE_ADJUST and DEFINE_HEAT_FLUX functions are assigned in the User Defined Function Hooks dialog box Note that the residual monitor for the UDS equation should be reduced from le 3 to le 6 before running the solution If the solution diverges then it may be due to the large source terms In this case the under relaxation factor should be reduced to 0 99 and the solution re run aak kk k CC k k k k k k kkk kk k k k k k k kkk kk k k K K K K RK aK Kk k k 2k 2k K 2k 2k 2 2k 2k k k Implementation of the P1 model using user defined scalars peaa o oo o kk kkk kkk k kkk 43k 2k include udf h include sg h Define which user defined scalars to use enum P1 N_REQUIRED_UDS static real abs_coeff 0 2 absorption coefficient Release 12 0 ANSYS Inc January 26 2009 8 45 Examples static real scat
466. main body of the DEFINE_PR_RATE function Typically if the particle surface reaction rate is described by rate f ruser iuser rate then the real function in this example reaction_rate should return f ruser iuser rate rate The variables cxboolean buser and char cuser can be used to control the flow of the program in cases of complicated rate definitions ratemin and ratemax hold the minimum and maximum possible values of the variable rate respectively They define the search interval where the numerical algorithm will search for the root of the equation as defined in the function reaction_rate The value of reaction rate rr will be refined until an accuracy specified by the value of tolerance tol is reached The variable ifail will take the value TRUE if the root of the function has not been found Hooking a Particle Reaction Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE PR_RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_rate will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 13 Hooking DEFINE_PR_RATE UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 63 DEFINE Macros 2 3 14 DEFINE_PRANDTL UDFs The following DEFINE macros can be used to specify Prandtl numbers i
467. mand in the libudf folder make FLUENT_ARCH ultra 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box You can use the UDF Library Manager dialog box to load and unload multiple shared libraries in ANSYS FLUENT Load the UDF Library To load a UDF library in ANSYS FLUENT open the UDF Library Manager dialog box Figure 5 5 1 5 24 Release 12 0 ANSYS Inc January 26 2009 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box Define gt User Defined Functions gt Manage UDF Library Manager UDF Libraries Library Name Figure 5 5 1 The UDF Library Manager Dialog Box In the UDF Library Manager dialog box type the name of the shared library in the Library Name field and click Load Figure 5 5 1 A message will be displayed in the console providing a status of the load process For example Opening library libudf Library libudf ntx86 3d libudf dl1l opened inlet_x_velocity Done indicates that the shared library named libudf was successfully loaded and contains one UDF named inlet_x_velocity In the UDF Library Manager dialog box the library name e g Libudf will be added under UDF Libraries Repeat this step to load additional libraries Release 12 0 ANSYS Inc January 26 2009 5 25 Compiling UDFs Unload the UDF Library To unload a UDF library in ANSYS FLUENT open the UDF Library Man
468. me Absolute x velocity m s ie udf inlet_x_velocity Y velocity m s 0 constant Figure 8 1 8 The Velocity Inlet Dialog Box 8 1 7 Step 6 Run the Calculation After initializing the solution run the calculation as usual EEEO 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results After the solution is run to convergence obtain a revised velocity field The velocity magnitude contours for the parabolic inlet x velocity are shown in Figure 8 1 9 and can be compared to the results of a constant velocity of 0 1 m s Figure 8 1 2 For the constant velocity condition the constant profile is seen to develop as the flow passes through the duct The velocity field for the imposed parabolic profile however shows a maximum at the center of the inlet which drops to zero at the walls 8 12 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples 0846 12 ANSYS 8 86e 02 7 87e 02 6 89e 02 5 9le 02 4 92e 02 3 94e 02 2 95e 02 1 976 02 9 84e 03 0 00e 00 Contours of Velocity Magnitude m s FLUENT 12 0 2d pbns lam Figure 8 1 9 Velocity Magnitude Contours for a Parabolic Inlet Velocity Pro file 8 2 Detailed UDF Examples This section contains detailed examples of UDFs that are used
469. me c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_K name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the kinetic energy Prandtl number to the solver Example The following UDF implements a high Re version of the RNG model using the k e option that is activated in ANSYS FLUENT Three steps are required 1 Set Cmu Cleps and C2eps as in the RNG model 2 Calculate Prandtl numbers for k and e using the UDF 3 Add the r source term in the e equation In the RNG model diffusion in k and equations appears as fe 0 Release 12 0 ANSYS Inc January 26 2009 2 65 DEFINE Macros while in the standard k e model it is given by Ht De r For the new implementation a UDF is needed to define a Prandtl number Pr as Ht a u p u in order to achieve the same implementation as the original RNG Model The following functions which are concatenated into a single C source code file demon strate this usage Note that the source code must be executed as a compiled UDF include udf h DEFINE_PRANDTL_K user_pr_k c t real pr_k alpha real mu C_MU_L
470. me of the UDF e g fixed_scalar_0 in the appropriate drop down list for the value you wish to set Release 12 0 ANSYS Inc January 26 2009 6 33 Hooking UDFs to ANSYS FLUENT Figure 6 2 18 The Fluid Dialog Box with Fixed Value Inputs for User Defined Scalars 6 34 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs e If you are using your UDF to define a specific value or flux for a scalar equation in a boundary condition dialog box you will first need to enter a nonzero number in the User Defined Scalars text box in the User Defined Scalars dialog box Define User Defined Scalars Next select the UDS tab in the wall inflow or outflow boundary dialog box Fig ure 6 2 19 Zone Name wall Adjacent Cell Zone Fluid J Momentum Thermal Radiation Species DPM Multiphase UDS User Defined Scalar Boundary Condition User Defined Scalar Boundary value User Scalar 0 Specified Value i User Scalar 0 JudF user_scalar libudf User Scalar 1 Specified Flux User Scalar 1 User Scalar 2 Specified Flux constant User Scalar 2 constant Figure 6 2 19 The Wall Dialog Box with Inputs for User Defined Scalars For each UDS User Scalar 0 User Scalar 1 etc specify the boundary condition value as a constant value or a UDF e g user_scalar libudf in the User Defined Scalar Boundary Value group box
471. min assumes a valid tmax and tmin has already been computed end_c_loop c tc Looping Over Faces For the purpose of discussing parallel ANSYS FLUENT faces can be categorized into two types interior faces and boundary zone faces Figure 7 2 2 Partition boundary faces are interior faces that lie on the partition boundary of a compute node s mesh begin end_f_loop is a face looping macro available in parallel ANSYS FLUENT that loops over all interior and boundary zone faces in a compute node The macro begin end_f_loop contains a begin and end statement and between these statements operations can be performed on each of the faces of the thread The macro is passed a face index f and face thread pointer tf Release 12 0 ANSYS Inc January 26 2009 7 25 Parallel Considerations begin_f_loop f tf end_f_loop f tf i begin_f_loop_int and begin f loop ext are looping macros that loop around interior and exterior faces in a compute node respectively The _int form is equivalent to begin f_loop_int Although these macros exist they do not have a practical application in UDFs and should not be used Recall that partition boundary faces lie on the boundary between two adjacent compute nodes and are represented on both nodes Therefore there are some computations e g summations when a partition boundary face will get counted twice in a face loop This can be corrected by testing whether the current node is a fa
472. mp double density double P double yil double s 0 0 double sum 0 0 double xiln_specs int i for i 0 i lt n_specs i xi i yili mvw i sum xili for i 0 i lt n_specs i xi i sum for i 0 i lt n_specs i if yi i gt SMLL s yili RKEOS_entropy temp mw i density MIXTURE_mw yi i UNIVERSAL_GAS_CONSTANT MIXTURE_mw yi xi i log xi i return s J Kg K double MIXTURE_viscosity double temp double density double P double yil double mu 0 int i for i 0 i lt n_specs i if yili gt SMLL mu yili RKEOS_viscosity temp i return mu Kg m s double MIXTURE_thermal_conductivity double temp double density double P double yi double kt 0 int i for i 0 i lt n_specs i 8 82 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples if yilil gt SMLL kt yili RKEOS_thermal_conductivity temp i return kt W m K FUNCTION MIXTURE_speed_of_sound Returns s o s given T and rho double MIXTURE_speed_of_sound double temp double density double P double yil double ples 0 double 0 double v fey R int i double cp MIXTURE_specific_heat temp density P yi for i 0 i lt n_specs i if yilil gt SMLL dvdp yili RKEOS_dvdp temp mw i
473. mpile a UDF then you must have Microsoft Visual Studio installed on your machine preferably on the C drive Also note that if you have compiled a UDF while running ANSYS FLUENT on a Win dows parallel network you must share the folder where the UDF is located so that all computers on the cluster can see this folder To share the folder in which the case data and compiled UDF reside using the Windows Explorer right click on the folder choose Sharing from the menu click Share this folder and then click OK i If you forget to enable the sharing option for the folder using the Windows Explorer then ANSYS FLUENT will hang when you try to load the library in the Compiled UDFs dialog box See Section 5 6 Common Errors When Building and Loading a UDF Library for a list of errors you can encounter that are specific to Windows parallel 5 28 Release 12 0 ANSYS Inc January 26 2009 Chapter 6 Hooking UDFs to ANSYS FLUENT After you have interpreted or compiled your UDF using the methods described in Chap ters 4 and 5 respectively you are ready to hook the function to ANSYS FLUENT using a graphic interface dialog box After it is hooked the function will be utilized in your ANSYS FLUENT model Details about hooking a UDF to ANSYS FLUENT can be found in the following sections Note that these sections relate to corresponding sections in Chapter 2 DEFINE Macros Section 6 1 Hooking General Purpose UDF s Section 6 2 Hooki
474. mpiled UDFs Usage DEF INE_EXECUTE_AFTER_CASE name libname or DEF INE_EXECUTE_AFTER_DATA name libname Argument Type Description symbol name UDF name char libname compiled UDF library name Function returns void There are two arguments to DEFINE_EXECUTE_AFTER_CASE and DEFINE_EXECUTE_AFTER_DATA name and libname You supply a name for the UDF which will be used by ANSYS FLU ENT when reporting that the EXECUTE_AFTER_CASE or EXECUTE_AFTER_DATA UDF is being run The libname is set by ANSYS FLUENT to be the name of the library e g libudf 2 16 Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros that you have specified by entering a name or keeping the default libudf libname is passed so that you can use it in messages within your UDF Example The following simple UDF named after_case and after_data prints a message to the console that contains the name of the library being loaded include udf h DEFINE_EXECUTE_AFTER_CASE after_case libname Message EXECUTE_AFTER_CASE called from s n libname J DEFINE_EXECUTE_AFTER_DATA after_data libname Message EXECUTE_AFTER_DATA called from s n libname Hooking an Execute After Reading Case and Data File UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE EXECUTE AFTER CASE or DEFINE_EXECUTE_AFTER_DATA is compiled Chapter 5 Compiling UDFs the function will not need to be hooked to ANSYS FLUENT t
475. mples To make use of this UDF in ANSYS FLUENT you will first need to interpret or compile the function and then hook it to ANSYS FLUENT using the graphical user interface Follow the procedure for interpreting source files using the Interpreted UDFs dialog box Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box or compiling source files using the Compiled UDFs dialog box Section 5 2 Compiling a UDF Using the GUI To hook the UDF to ANSYS FLUENT as the velocity boundary condition for the zone of choice open the Velocity Inlet dialog box and click the Momentum tab Figure 8 2 4 EME velocity inlet Edit Velocity Inlet zone Name velocity inlet Momentum Thermal Radiation Species DPM Multiphase UDS velocity Specification Method Components Reference Frame Absolute x velocity m s ud inlet_x_velocity Velocity m s 0o constant Figure 8 2 4 The Velocity Inlet Dialog Box In the X Velocity drop down list select udf inlet_x_velocity the name that was given to the function above with udf preceding it Click OK to accept the new boundary condition and close the dialog box The user profile will be used in the subsequent solution calculation After the solution is initialized and run to convergence a revised velocity field is obtained as shown in Figures 8 2 5 and 8 2 6 The velocity field shows a maximum at the
476. n of NUT is available n if NNULLP THREAD_STORAGE t SV_Y_I ns SV_Y_0_G SV_Y_0 Message0 show grad Gradient of Species d is available n ns 3 14 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Reconstruction Gradient RG Vector Macros Table 3 2 10 shows a list of cell reconstruction gradient vector macros Like gradient variables RG variables are available only when the equation for that variable is being solved As in the case of gradient variables you can retain all of the reconstruction gradient data by issuing the text command solve set expert and then answering yes to the question Keep temporary solver memory from being freed Note that when you do this the reconstruction gradient data is retained but the calculation requires more memory to run You can access a component of a reconstruction gradient vector by specifying it as an argument in the reconstruction gradient vector call 0 for the z component 1 for y and 2 for z For example C_T_RG c t 0 returns the x component of the cell temperature reconstruction gradient vector returns the x component of the temperature reconstruction gradient vector Table 3 2 10 Macros for Cell Reconstruction Gradients RG Defined in mem h Macro Argument Types Returns C_R_RG c t cell_t c Thread t density RG vector C_P_RG c t cell t c Thread t pressure RG vector C_U_RG c t cell_t c Thread
477. n begin begin Release 12 0 ANSYS Inc January 26 2009 boundary face area normals direction 3 23 boundary face partition 7 8 boundary zone faces partitioned mesh 7 28 BOUNDARY_FACE_GEOMETRY 3 27 8 44 BOUNDARY FACE THREAD P 2 232 3 28 BOUNDARY_SECONDARY_GRADIENT_SOURCE 3 28 8 44 building a shared library 5 1 5 2 5 5 5 8 8 10 C compiler 5 2 C preprocessor 4 1 4 4 8 7 C programming 1 1 arrays A 8 casting A 7 commenting code A 2 constants A 3 control statements A 10 for loops A 11 if A 10 if else A 10 data types A 2 define A 17 example 8 4 file inclusion A 17 FORTRAN comparison with A 18 functions A 7 A 13 fclose A 15 fopen A 14 fprintf A 15 fscanf A 16 input output I O A 14 mathematical A 13 printf A 15 trigonometric A 13 Index 1 Index include A 17 macro substitution A 17 operators A 12 arithmetic A 12 logical A 12 pointers A 8 as function arguments A 9 variables A 3 declaring A 4 external A 4 global A 3 local A 3 static A 6 typedef A 7 C_CENTROID 2 18 2 19 2 101 3 6 3 60 CCP 2 143 C_D 2 65 2 126 3 8 CDP 2 152 C_FACE 2 177 3 7 3 58 cface_loop 2 115 2 117 3 58 C_FACE_THREAD 2 115 2 117 2 177 3 7 3 58 C_FMEAN 2 122 C_H 3 8 C K 2 65 2 126 3 8 CKL 2 143 C_MU_EFF 2 35 C MULL 2 65 2 141 2 143 C_MU_T 2 65 C_NFACES 3 7 C_NNODES 3 7 C_NODE 3 59 c_node loop 3 59 C_NUT 3 8 C_O 3 8 C P 3
478. n register Thread t register cell_t c Message Computing Storing cell Tmax values n domain Get_Domain 1 Store User Defined Tmax at each cell if ud_sox_do_once 1 if m_udm lt N_REQUIRED_UDM Error Not enough udm allocated n thread_loop_c t domain begin_c_loop c t C_UDMI c t CELL_TMAX ud_eval_cell_tmax c t end_c_loop c t ud_sox_do_once Q Message Computing cell Tmax values completed n Hooking a SO Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SOX_RATE is compiled Chapter 5 Com piling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_sox will become visible and selectable in the SOx Model dialog box in ANSYS FLUENT See Section 6 2 20 Hooking DEFINE_SOX_RATE UDFs for details 2 1 12 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros 2 3 21 DEFINE_SPECIFIC_HEAT Description The DEFINE_SPECIFIC_HEAT macro can be used to define temperature dependent func tions for specific heat and sensible enthalpy for fluid solid and mixture materials this does not include DPM particles These functions must be defined in a consistent man ner that is the enthalpy function should be the temperature integral of the specific heat function This option is not available with the premixed non premixed and partially premixed models and should be used as a compiled UDF only
479. n this is done by the ANSYS FLUENT solver using the reaction rate supplied by your UDF The following is a source code template that shows how to use DEFINE_VR_RATE in con nection with more than one user specified reaction Note that ANSYS FLUENT always calculates the rr and rr_t reaction rates before the UDF is called Consequently the values that are calculated are available only in the given variables when the UDF is called Release 12 0 ANSYS Inc January 26 2009 2 1 31 DEFINE Macros paaa oo ooo o kkk kk A A A kkk kkk kkk A A A kk kkk kk k Multiple reaction UDF that specifies different reaction rates for different volumetric chemical reactions BO RK RK a a kk ak 2k 2k a 3k 2k 2k a ak 2k ak kk include udf h DEFINE_VR_RATE myrate c t r mw yi rr rr_t If more than one reaction is defined it is necessary to distinguish between these using the names of the reactions if strcmp r gt name reaction 1 Reaction 1 else if strcmp r gt name reaction 2 Reaction 2 else Message Unknown Reaction n Message Actual Reaction s n r gt name Hooking a Volumetric Reaction Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_VR_RATE is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g myrate will become visible and
480. n ANSYS FLUENT for single phase flows DEF INE_PRANDTL_D Description You can use DEFINE PRANDTL_D to specify Prandtl numbers for turbulent dissipation Usage DEFINE_PRANDTL_D name c t Argument Type Description symbol name UDF name cell_t c Index of cell on which the Prandtl number function is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_PRANDTL_D name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the turbulent dissipation Prandtl number to the solver Example An example of a Prandtl_D UDF is provided below in the source listing for DEFINE_PRANDTL_K Hooking a Prandtl Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_PRANDTL_D is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g user_pr_d will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 14 Hooking DEFINE PRANDTL UDFs for details 2 64 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros DEF INE_PRANDTL_K Description You can use DEFINE PRANDTL_K to specify Prandtl numbers for turbulence kinetic energy k Usage DEFINE_PRANDTL_K na
481. n Rate Function drop down list in the User Defined Function Hooks dialog box Figure 6 2 36 8 38 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux none Volume Reaction Rate yo reac_rate libudf Figure 8 2 26 The User Defined Functions Hooks Dialog Box Initialize and run the calculation The converged solution for the mass fraction of species a is shown in Figure 8 2 27 The gas that moves through the porous region is gradually converted to species b in the horizontal section of the duct No reaction takes place in the fluid region although some diffusion of species b out of the porous region is suggested by the wide transition layer between the regions of 100 and 0 species a Release 12 0 ANSYS Inc January 26 2009 8 39 Examples 1 00e 00 wo 00e 01 00e 01 7 00e 01 6 00e 01 5 00e 01 4 00e 01 3 00e 01 2 00e 01 1 00e 01 1 766 11 Contours of Mass fraction of species a FLUENT 12 0 2d pbns spe lam Figure 8 2 27 Mass Fraction for species a Governed by a Reaction in a Porous Region 8 2 5 User Defined Scalars This section contains exam
482. n of species 7 in reaction r A DEFINE_NET_REACTION_RATE UDF may be used for the laminar finite rate with stiff chemistry enabled EDC and PDF Transport models as well as for the surface chemistry model In contrast the volumetric UDF function DEFINE_VR_RATE and surface UDF function DEFINE_SR_RATE are used for the laminar finite rate model when stiff chemistry is disabled Usage DEFINE NET REACTION RATE name c t particle pressure temp yi rr jac Argument Type Description symbol name UDF name cell tc Cell index of current particle Thread t Pointer to cell thread for particle Particle particle Pointer to Particle data structure that contains data related to the particle being tracked double pressure Pointer to pressure variable double temp Pointer to temperature variable double yi Pointer to array containing species mass fractions double rr Pointer to array containing net molar reaction rates double jac Pointer to array of Jacobians Function returns void There are nine arguments to DEFINE NET REACTION RATE name c t particle pressure temp yi rr and jac You supply name the name of the UDF The variables c t particle pressure temp yi rr and jac are passed by the ANSYS FLUENT solver to your UDF and have SI units The outputs of the function are the array of net molar 2 50 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros reaction rates rr with units kmol m
483. n to be taken in braces cell_t c Thread t face_t f Thread tf int n c_face_loop c t n loops over all faces of a cell f C_FACE c t n tf C_FACE_THREAD c t n The argument n is the local face index number The local face index number is used in the C_FACE macro to obtain the global face number e g f C_FACE c t n Another useful macro that is often used in c_face_loop is C_FACE THREAD This macro is used to reference the associated face thread e g tf C_FACE_THREAD c t n Refer to Section 3 8 Miscellaneous Macros for other macros that are associated with c_face_loop 3 58 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros Looping Over Nodes of a Cell c_node_loop c_node_loop c t n is a function that loops over all nodes of a given cell It consists of a single loop statement followed by the action to be taken in braces Example cell_t c Thread t int n Node node c_node_loop c t n node C_NODE c t n Here n is the local node index number The index number can be used with the C_NODE macro to obtain the global cell node number e g node C_NODE c t n Looping Over Nodes of a Face f node_loop f node loop f t n is a function that loops over all nodes of a given face It consists of a single loop statement followed by the action to be taken in braces Example face_t f Thread t int n Node node f_node_loop
484. n your UDF and then recompiling the UDF This can be a tedious process if you want to apply the UDF to a number of zones By defining your own scheme variable if you want to alter the variable later then you can do it from the text interface using a Scheme command Macros that are used to define and access user specified Scheme variables from the text interface are identified by the prefix rp e g rp var define Macros that are used to access user defined Scheme variables in an ANSYS FLUENT solver are identified by the prefix RP e g RP_Get_Real These macros are executed within UDFs 3 6 1 Defining a Scheme Variable in the Text Interface To define a scheme variable named pres_av thread id in the text interface you can use the scheme command rp var define pres_av thread id 2 integer f Before you define a scheme variable it is often good practice to check that the variable is not already defined You can do this by typing the following command in the text window if not rp var object pres_av thread id rp var define pres_av thread id 2 integer f This command first checks that the variable pres_av thread id is not already defined and then sets it up as an integer with an initial value of 2 Note that the string is allowed in Scheme variable names as in pres_av thread id and is a useful way to organize variables so that they do not interfere with each other Release 12 0 ANSYS Inc Ja
485. nET 8 2 20 0 where H T is the enthalpy function for a thermally perfect gas i e enthalpy is a function of temperature alone In the present case we employ a fourth order polynomial for the specific heat for a thermally perfect gas 8 CHT Cy OT 03T Cyl CT 8 2 21 8 50 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples and obtain the enthalpy from the basic relation T HT C T dT 8 2 22 To The result is 0 1 2 1 3 1 4 1 5 0 770 HT CiT 5C2T 30T FCaT CsT H T 8 2 23 Note that H T is the enthalpy at a reference state p T which can be chosen arbitrarily The specific heat for the real gas can be obtained by differentiating Equation 8 2 20 with respect to temperature at constant pressure OH Cp ar 8 2 24 The result is av da T 1 n V p F Op CHT 5 R by in V HADU n 8 2 25 Finally the derivative of enthalpy with respect to pressure at constant temperature can be obtained using the following thermodynamic relation 8 OH OV FF ava or 8 2 26 Following 1 the entropy can be expressed in the form da T V b aT V bo 0 0 Z S S T p Rin yo F ln V 8 2 27 Entropy Release 12 0 ANSYS Inc January 26 2009 8 51 Examples where the superscript 0 again refers to a reference state where the ideal gas law is appli cable For an ideal ga
486. n_specs i Message0 n MIXTURE_Setup Specie d s n i gas i concatenate species name into one string and send back to fluent strcat specielist gas 0 for i 1 i lt n_specs i strcat specielist strcat specielist gas i 8 68 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples double MIXTURE_density double Temp double P double yi double Rgas Mixture_Rgas yi double r P Rgas Temp Density at Temp amp P return r Kg m73 double MIXTURE_specific_heat double Temp double density double P double yi double cp 0 0 int i for i 0 i lt n_specs i cp yi i Cp_i Temp density i return cp J Kg K double MIXTURE_enthalpy double Temp double density double P double yi double h 0 0 int i for i 0 i lt n_specs i h yi i Temp Cp_i Temp density i return h J Kg double MIXTURE_entropy double Temp double density double P double yil double s 0 0 double Rgas 0 0 Rgas Mixture_Rgas yi n I MIXTURE_specific_heat Temp density P yi log Temp ref_T Rgas log P ref_p Release 12 0 ANSYS Inc January 26 2009 8 69 Examples return s J Kg K double MIXTURE_mw double yil double MW sum 0 0 int i for i 0 i lt n_specs i sum yili Mw_i i MW 1 0 MAX sum SMALL return MW Kg Kmol
487. nally select the function name e g custom slip libudf from the list of UDFs displayed in the User Defined Functions dialog box Figure 6 3 9 and click OK The UDF name will appear in the text box below the Slip Velocity drop down list in the Phase Interaction dialog box Click OK to close the Phase Interaction dialog box See Section 2 4 5 DEFINE VECTOR EXCHANGE PROPERTY for details about DEF INE_VECTOR_EXCHANGE_PROPERTY functions 6 62 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 Hooking Discrete Phase Model DPM UDFs This section contains methods for hooking UDFs to ANSYS FLUENT that have been e defined using DEFINE macros described in Section 2 5 Discrete Phase Model DPM DEFINE Macros and e interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 4 1 Hooking DEFINE _DPM_BC UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_BC UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the appropriate boundary condition dialog box Figure 6 4 1 in ANSYS FLUENT To hook the UDF first create an injection using the Injections dialog box Define Injections Next open the Boundary Conditions task page gt Boundary Conditions Select the boundary in the Zone list and click Edit to open the boundary condit
488. name cell tc Cell index Thread t Pointer to cell thread real T Temperature int nb Band number real emissivity_weighting factor The emissivity weighting factor in the emission term of the RTE for the non gray DO model Equation 5 3 39 in the separate Theory Guide Function returns void There are six arguments to DEFINE_EMISSIVITY_WEIGHTING_FACTOR name c t T nb emissivity weighting factor You supply name the name of the UDF c t T nb and emissivity_weighting factor are variables that are passed by the ANSYS FLU ENT solver to your UDF DEFINE_EMISSIVITY_WEIGHTING_FACTOR is called by ANSYS FLUENT for each cell Example In the following UDF named em_wt the emissivity weighting factor present in the emission term of the RTE for the non gray DO model is modified The UDF is called for all of the cells It modifies the emissivity weighting factor so that it is no longer the value calculated internally by ANSYS FLUENT but is instead changed to 1 UDF to alter the emissivity weighting factor for the non gray DO model include udf h DEFINE_EMISSIVITY_WEIGHTING_FACTOR em_wt c t T nb emissivity_weighting factor revise the calculated emissivity_weighting factor to be a value of 1 xemissivity_weighting_factor 1 0 2 42 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Hooking a Emissivity Weighting Factor UDF to ANSYS FLUENT After the UDF that you have define
489. nd Read Case 7 Write Case Read Data Write Data Execute at Exit Turbulent Premixed Source Ignition Source SIRs eT v Figure 6 2 12 The User Defined Function Hooks Dialog Box Select the function name e g ign_udf_src libudf in the Ignition Source drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 10 DEFINE_IGNITE_SOURCE for details about DEFINE_IGNITE_SOURCE func tions 6 2 11 Hooking DEFINE NET REACTION RATE UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE NET REACTION RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 13 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first set up the species transport and combustion models Teta See Edit 6 26 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs Note that net reaction rate UDFs may only be used with the laminar finite rate model with stiff chemistry enabled the EDC model the PDF Transport model or the surface chemistry model Therefore you must use one of the following groups of settings in the Species Model dialog box e To enable the laminar finite rate model select Species Transport enable Volumetric in the Reactions group box select Laminar Finite Rate in the Turbulence Chemistry Interac
490. nd NV_MAG2 The utility NV_MAG computes the magnitude of a vector This is taken as the square root of the sum of the squares of the vector components NV_MAG x 2D sqrt x 0 x 0 x 1 x 1 3D sqrt x 0 x 0 x 1 x 1 x 2 x 2 The utility NV_MAG2 computes the sum of squares of vector components NV_MAG2 x 2D x 0 x 0 x 1 x 1 3D x 0 x 0 x 1 x 1 x 2 x 2 See Section 2 5 1 DEFINE_DPM_BC for an example UDF that utilizes NV_MAG 3 72 Release 12 0 ANSYS Inc January 26 2009 3 4 Vector and Dimension Macros Dot Product The following utilities compute the dot product of two sets of vector components ND_DOT x y z u v w 2D x u y v 3D x u y v z w NV_DOT x u 2D x 0 u 0 x 1 u 1 3D x 0 u 0 x 1 u 1 x 2 u 2 NVD_DOT x u v w 2D x 0 u x 1 v 3D x 0 u x 1 v x 2 w See Section 2 3 6 DEFINE_DOM_SPECULAR_REFLECTIVITY for an example UDF that utilizes NV_DOT Cross Product For 3D the CROSS macros return the specified component of the vector cross product For 2D the macros return the cross product of the vectors with the z component of each vector set to 0 ND_CROSS_X x0 x1 x2 y0 y1 y2 2D 0 0 3D C x1 Cy2 Cy1 x2 ND_CROSS_Y x0 x1 x2 y0 y1 y2 2D 0 0 3D C x2 y0 Cy2 x0 ND_CROSS_Z x0 x1 x2 y0 y1 y2 2D and 3D x0 y1 y0 x1 NV_CROSS_X x y Release 12 0 ANSYS Inc Janu
491. nd kp respectively in the Arrhenius form kp 1 2e8 39765 575 RT k 1 0e4T 1e 10464 625 RT The O atom concentration in the gas phase 0 is computed using the partial equilibrium assumption which states Oeq 36 6470 5 27123 0 RT O where O2 is the molar concentration of oxygen Here all units are in m gmol J sec Release 12 0 ANSYS Inc January 26 2009 2 1 07 DEFINE Macros The function so2_so3_rate is used to compute the forward and reverse rates for both SO and SOs3 The rate of release of SO from volatiles S50 volatile is given by LO00P volatile Y5 volatile Ys s02 Mw sV SSOz volatile where fyolatile is the rate of release of volatiles in kg sec Ys volatile is the mass fraction of sulfur species in volatiles Ys so is the mass fraction of fuel S that converts to SO2 Mw s is the molecular weight of sulfur in kg kg mol and V is the cell volume in m See Section 3 2 7 SO Macros for details about the SO macros e g POLLUT_EQN MOLECON ARRH that are used in pollutant rate calculations in this UDF peaa ooo o o kkk k kkk kkk kk kkk kkk kkk k UDF example of User Defined SOx Rate for ANSYS FLUENT 12 or later If used with the Replace with UDF radio button activated this UDF will replace the default fluent SOx rates The flag Pollut_Par gt pollut_io_pdf IN_PDF should always be used for rates other than that from char N so that if requested the contributions
492. ndary Secondary Gradient Source BOUNDARY_SECONDARY_GRADIENT_SOURCE The use of this macro first requires that cell geometry information be defined which can be readily ob tained by the use of a second macro BOUNDARY FACE GEOMETRY see Section 3 2 5 Bound ary Face Geometry BOUNDARY_FACE_GEOMETRY You will see these macros called in the UDF that defines the wall boundary condition for G To complete the implementation of the P1 model the radiation energy equation must be coupled with the thermal energy equation This is accomplished by modifying the source term and wall boundary condition of the energy equation Consider first how the energy equation source term must be modified The gradient of the incident radiation is proportional to the radiative heat flux A local increase or decrease in the radiative heat flux is attributable to a local decrease or increase in thermal energy via the absorption and emission mechanisms The gradient of the radiative heat flux is therefore a negative source of thermal energy The source term for the incident radiation Equation 8 2 7 is equal to the gradient of the radiative heat flux and hence its negative specifies the source term needed to modify the energy equation see Section 5 3 3 P 1 Radiation Model Theory in the separate Theory Guide for more details Now consider how the energy boundary condition at the wall must be modified Locally the only mode of energy transfer from the wall to the flu
493. ndex vap_rate mp Cp gas enthalpy source term dzdt gt energy hgas gas_index vap_rate P_total cvap_surf ns dens_total cvap_surf ns molwt gas_index multicomponent boiling P_total Z UNIVERSAL_GAS_CONSTANT Tp Release 12 0 ANSYS Inc January 26 2009 2 1 75 DEFINE Macros if P_total gt c gt pressure amp amp dydt 0 gt 0 real h_boil dydt 0 mp Cp keep particle temperature constant dydt 0 0 for ns 0 ns lt nc ns int gas_index TP_COMPONENT_INDEX_I p ns if gas_index gt 0 real boil_rate h_boil hvap gas_index cvap_surf ns molwt gas_index dens_total particle component mass source term dydt 1 ns boil_rate fluid species source dzdt gt species gas_index boil_rate fluid energy source dzdt gt energy hgas gas_index boil_rate Hooking a DPM Particle Heat and Mass Transfer UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_HEAT_MASS is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g multivap will become visible in the Set Injection Properties dialog box in ANSYS FLUENT See Section 6 4 5 Hooking DEFINE_DPM_HEAT_MASS UDFs for details on how to hook your DEFINE_DPM_HEAT_MASS UDF to ANSYS FLUENT 2 1 76 Release 12 0 ANSYS Inc Janua
494. ne Options viscous Heating Energy Prandtl Number none Law of the Wall user_log_law libudf Figure 6 2 37 The Viscous Model Dialog Box To hook the UDF select k epsilon from the Model list in the Viscous Model dialog box and select User Defined Wall Functions from the Near Wall Treatment list Then select the function name e g user_log_law libudf from the Law of the Wall drop down list and click OK See Section 2 3 28 DEFINE_WALL_FUNCTIONS for details about defining DEFINE_WALL_FUNCTIONS functions in ANSYS FLUENT 6 54 Release 12 0 ANSYS Inc January 26 2009 6 3 Hooking Multiphase UDFs 6 3 Hooking Multiphase UDFs This section contains methods for hooking UDFs to ANSYS FLUENT that have been defined using DEFINE macros described in Section 2 4 Multiphase DEFINE Macros and interpreted or compiled using methods described in Chapters 4 or 5 respectively 6 3 1 Hooking DEFINE_CAVITATION_RATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE CAVITATION RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Func tion Hooks dialog box Figure 6 3 2 in ANSYS FLUENT Note that cavitation rate UDFs can be applied only to the mixture multiphase model To hook the UDF to ANSYS FLUENT you will first need to open the Multiphase Model dialog
495. ned Functions Initialization init_bubbles libudf v Figure 6 4 6 The Injections Dialog Box 6 70 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 7 Hooking DEFINE_DPM_LAW UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_LAW UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Custom Laws dialog box Figure 6 4 7 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first create a particle injection in the Injections dialog box Define Injections Click Create in the Injections dialog box to open the Set Injection Properties dialog box Then enable the Custom option in the Laws group box in the Set Injection Properties dialog box in order to open the Custom Laws dialog box Figure 6 4 7 Custom Laws JEvapor_Swelling_Law slibudF First Law Inactive Second Law Inactive Third Law Inactive Fourth Law Inactive Fifth Law Inactive Sixth Law Inactive Seventh Law Inactive Eighth Law J Inactive Ninth Law Inactive Tenth Law Default Switching Figure 6 4 7 The Custom Laws Dialog Box In the Custom Laws dialog box select the function name e g Evapor_Swelling_Law libudf from the appropriate drop down list located to the left
496. need to get the integer ID of the zone by visiting the boundary condition dialog box e g Fluid and noting the zone ID You can also obtain the value of the Zone ID from the solver using RP_Get_Integer Note that in order to use RP_Get_Integer you will have had to define the zone ID variable first either in another UDF using RP_Set_Integer or on the Scheme side using rp var define see Section 3 6 Scheme Macros for details Next you supply the zone_ID as an argument to Lookup_Thread either as a hard coded integer e g 1 2 or as the variable assigned from RP_Get_Integer Lookup Thread returns the pointer to the thread that is associated with the given zone ID You can then assign the thread pointer to a thread_name and use it in your UDF Fa Note that when Lookup_Thread is utilized in a multiphase flow problem the domain pointer that is passed to the function depends on the UDF that it is contained within For example if Lookup Thread is used in an adjust function DEFINE ADJUST then the mixture domain is passed and the thread pointer returned is the mixture level thread Example Below is a UDF that uses Lookup_Thread In this example the pointer to the thread for a given zone_ID is retrieved by Lookup_Thread and is assigned to thread The thread pointer is then used in begin f loop to loop over all faces in the given thread and in F_CENTROID to get the face centroid value PERO FA AOR CCC I IOI OK AK AK AE ACA A A 1 1 KK KKK kkk
497. ng Model Specific UDFs Section 6 3 Hooking Multiphase UDF s Section 6 4 Hooking Discrete Phase Model DPM UDFs Section 6 5 Hooking Dynamic Mesh UDFs Section 6 6 Hooking User Defined Scalar UDS Transport Equation UDFs Section 6 7 Common Errors While Hooking a UDF to ANSYS FLUENT 6 1 Hooking General Purpose UDFs This section contains methods for hooking general purpose UDFs to ANSYS FLUENT General purpose UDFs are those that have been defined using macros described in Sec tion 2 2 General Purpose DEFINE Macros and then interpreted or compiled and loaded using methods described in Chapters 4 or 5 respectively Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking UDFs to ANSYS FLUENT 6 1 1 Hooking DEFINE_ADJUST UDFs After you interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_ADJUST UDF the name of the function you supplied as a DEFINE macro argument can be hooked using the User Defined Function Hooks dialog box Figure 6 1 1 Note that you can hook multiple adjust UDFs to your model if desired To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 1 1 Define User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data rone Execute at Exit Wall Heat Flux Figure
498. nitializing Injection s n I gt name loop p I gt p Standard ANSYS FLUENT Looping Macro to get particle streams in an Injection t cell P_CELL p Get the cell and thread that the particle is currently in cthread P_CELL_THREAD p Set up molecular weight amp mass fraction arrays mix THREAD_MATERIAL cthread mixture_species_loop mix sp i mw i yilil MATERIAL_PROP sp PROP_mwi C_YI cell cthread i area contact_area cell cthread REACTING_SURFACE_ID amp count Function that gets total area of REACTING_SURFACE faces in contact with cell count is the number of contacting faces and is needed to share the total bubble emission between the faces if count gt 0 if cell is in contact with REACTING_SURFACE P_FLOW_RATE p area MW_H2 STOIC_H2 reaction_rate cell cthread mw yi real count to get correct total flow rate when multiple faces contact the same cell Release 12 0 ANSYS Inc January 26 2009 2 1 79 DEFINE Macros P_DIAM p 1e 3 P_RHO p 1 0 P_MASS p P_RHO p M_PI pow P_DIAM p 3 0 6 0 else P_FLOW_RATE p 0 0 real contact_area cell_t c Thread t int s_id int n int i 0 real area 0 0 A ND_ND n 0 c_face_loop c t i if THREAD_ID C_FACE_THREAD c t i s_id n F_AREA A C_FACE c t i C_FACE_THREAD c t i area NV_MAG A return area Hooking
499. ns This is critical for optimal performance since this function gets called numerous times during an iteration cycle It should be noted that the value of the exponent n in the function a T will depend on the substance A table of values can be found in 1 for some common substances Alternatively 1 states that values of n are well correlated by the empirical equation n 0 4986 1 1735w 0 475w 8 2 14 where w is the acentric factor defined as w log 20 1 0 8 2 15 Pe In the above equation p T is the saturated vapor pressure evaluated at temperature T 0 7T Release 12 0 ANSYS Inc January 26 2009 8 49 Examples Derivatives of Specific Volume and Density The derivatives of specific volume with respect to temperature and pressure can be easily determined from Equation 8 2 12 using implicit differentiation The results are presented below OV a1 V a2 V as 8 2 16 Op T 3V2 T 2a V ag OV i a r V pg a2 V a3 r 8 2 17 oT p 3V2 2a1V ag where E RT RTbo a T a T b a F ay I ay P P R n da T b da T a T a r gt a2 7 a3 7 dT p aT n T The derivatives of density can be obtained from the above using the relations 3 5 Sa9 8 2 18 T Op j r Op OV a Ses ae 2 1 sr ar on p p Specific Heat and Enthalpy Following 1 enthalpy for a real gas can be written T b H HT pV RT a
500. ns and there fore may not provide satisfactory values of viscosity and thermal conductivity for certain applications You are encouraged to modify these functions in the UDRGM source code if alternate formulae are available for a given gas Using the Redlich Kwong Real Gas UDRGM Using the Redlich Kwong Real Gas UDRGM simply requires the modification of the top block of define macros to provide the appropriate parameters for a given substance An example listing for CO is given below The parameters required are MWT Molecular weight of the substance PCRIT Critical pressure Pa TCRIT Critical temperature K ZCRIT Critical compressibility factor VCRIT Critical specific volume m kg NRK Exponent of a T function CC1 CC2 CC3 CC4 CC5 Coefficients of Cp T polynomial curve fit P_REF Reference pressure Pa T_REF Reference temperature K The coefficients for the ideal gas specific heat polynomial were obtained from 8 coeff cients for other substances are also provided in 8 After the source listing is modified the UDRGM C code can be recompiled and loaded into ANSYS FLUENT in the manner described earlier Release 12 0 ANSYS Inc January 26 2009 8 53 Examples The variables below need to be set for a particular gas C02 REAL GAS EQUATION OF STATE MODEL BASIC VARIABLES ALL VARIABLES ARE IN SI UNITS define RGASU UNIVERSAL_GAS_CONSTANT define PI 3 141592654
501. ns group box e g Flength and click OK See Section 2 3 23 DEFINE_TRANS UDFs for details about DEFINE_TRANS functions Release 12 0 ANSYS Inc January 26 2009 6 49 Hooking UDFs to ANSYS FLUENT 6 2 24 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_TURB_PREMIX_SOURCE UDF the name of the function you sup plied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 33 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 33 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Turbulent Premixed Source faprmgr pamm Figure 6 2 33 The User Defined Function Hooks Dialog Box You must have a premixed combustion model enabled in the Species Model dialog box Select the function name e g turb_flame src libudf in the Turbulent Premixed Source Function drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 24 DEFINE_TURB_PREMIX_SOURCE for details about DEFINE_TURB_PREMIX_SOURCE functions 6 50 Release 12 0 ANSYS Inc January 26 2009 6 2 Hook
502. nuary 26 2009 3 77 Additional Macros for Writing UDFs 3 6 2 Accessing a Scheme Variable in the Text Interface After you define a Scheme variable in the text interface you can access the variable For example if you want to check the current value of the variable e g pres_av thread id on the Scheme side you can type the following command in the text window rpgetvar pres_av thread id i It is recommended that you use rpgetvar when you are retrieving an ANSYS FLUENT variable using a scheme command This will ensure that you access the current cached value 3 6 3 Changing a Scheme Variable to Another Value in the Text Interface Alternatively if you want to change the value of the variable you have defined pres_av thread id to say 7 then you will need to use rpsetvar and issue the follow ing command in the text window rpsetvar pres_av thread id 7 3 6 4 Accessing a Scheme Variable in a UDF After a new variable is defined on the Scheme side using a text command you will need to bring it over to the solver side to be able to use it in your UDF RP macros are used to access Scheme variables in UDFs and are listed below RP_Get_Real variable name Returns the double value of variable name RP_Get_Integer variable name Returns the integer value of variable name RP_Get_String variable name Returns the char value of variable name RP_Get_Boolean variable name Returns the Boolean value of variab
503. o ANSYS FLUENT 6 26 DEFINE_NOX_RATE UDFs defining 2 52 hooking to ANSYS FLUENT 6 28 DEFINE_ON_DEMAND UDFs defining 2 20 example 3 10 hooking to ANSYS FLUENT 6 10 DEFINE_PR_RATE UDFs defining 2 58 hooking to ANSYS FLUENT 6 29 DEFINE_PRANDTL UDFs defining 2 64 hooking to ANSYS FLUENT 6 31 DEFINE_PROFILE UDFs defining 2 72 example 8 16 8 45 hooking to ANSYS FLUENT 6 32 DEFINE_PROPERTY UDF s defining 2 87 example 8 31 hooking to ANSYS FLUENT 6 36 Release 12 0 ANSYS Inc January 26 2009 DEFINE_RW_FILE UDFs defining 2 23 hooking to ANSYS FLUENT 6 11 DEFINE_SCAT_PHASE_FUNC UDFs defining 2 95 hooking to ANSYS FLUENT 6 38 DEFINE_SDOF_PROPERTIES UDF s defining 2 221 hooking to ANSYS FLUENT 6 88 DEFINE_SOLAR_INTENSITY UDFs defining 2 98 hooking to ANSYS FLUENT 6 40 DEFINE SOURCE UDFs defining 2 100 example 8 25 hooking to ANSYS FLUENT 6 42 DEFINE_SOX_RATE UDFs defining 2 106 hooking to ANSYS FLUENT 6 44 DEFINE_SPECIFIC_HEAT UDFs defining 2 113 hooking to ANSYS FLUENT 6 46 DEFINE_SR_RATE UDFs defining 2 114 hooking to ANSYS FLUENT 6 47 DEFINE_TRANS UDFs defining 2 118 hooking to ANSYS FLUENT 6 49 DEF INE_TURB_PREMIX_SOURCE UDF s defining 2 122 hooking to ANSYS FLUENT 6 50 DEFINE_TURB_SCHMIDT UDF defining 2 124 DEF INE_TURB_SCHMIDT UDFs hooking to ANSYS FLUENT 6 51 DEF INE_TURBULENT_VISCOSITY UDFs defining 2 125 hooking to ANSYS FLUENT 6 52
504. o M_PI to get the desired value Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros 3 2 2 Node Macros A mesh in ANSYS FLUENT is defined by the position of its nodes and how the nodes are connected The macros listed in Table 3 2 1 and Table 3 2 2 can be used to return the real Cartesian coordinates of the cell node at the cell corner in SI units The variables are available in both the pressure based and the density based solver Definitions for these macros can be found in metric h The argument Node node for each of the variables defines a node Node Position Table 3 2 1 Macros for Node Coordinates Defined in metric h Macro Argument Types Returns NODE_X node Node node real x coordinate of node NODE_Y node Node node real y coordinate of node NODE_Z node Node node real z coordinate of node Number of Nodes in a Face F_NNODES The macro F_NNODES shown in Table 3 2 2 returns the integer number of nodes associated with a face Table 3 2 2 Macro for Number of Nodes Defined in mem h Macro Argument Types Returns F_NNODES f t face_t f Thread t int number of nodes in a face Release 12 0 ANSYS Inc January 26 2009 3 5 Additional Macros for Writing UDFs 3 2 3 Cell Macros The macros listed in Table 3 2 3 3 2 19 can be used to return real cell variables in SI units They are identified by the C_ prefix These variables are available in
505. o Section 1 10 1 Multiphase specific Data Types and in particular Figure 1 10 1 for a discussion on hierarchy of structures within ANSYS FLUENT 3 64 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros Phase Domain Pointer DOMAIN_SUB_DOMAIN There are two ways you can get access to a specific phase or subdomain pointer within the mixture domain You can use either the DOMAIN_SUB_DOMAIN macro described below or Get_Domain which is described below DOMAIN_SUB_DOMAIN has two arguments mixture_domain and phase domain_index The function returns the phase pointer subdomain for the given phase_domain_index Note that DOMAIN_SUB_DOMAIN is similar in implementation to the THREAD_SUB_THREAD macro described in Section 3 3 2 Phase Level Thread Pointer THREAD_SUB_THREAD int phase_domain_index 0 primary phase index is 0 Domain mixture_domain Domain subdomain DOMAIN_SUB_DOMAIN mixture_domain phase_domain_index mixture_domain is a pointer to the mixture level domain It is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that con tains a domain variable argument e g DEFINE_ADJUST and your UDF is hooked to the mixture Otherwise if the mixture_domain is not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 before calling sub_domain_loop phase_domain_index is an index of subdomain pointers It is an int
506. odel dialog box 6 44 SOx rate UDFs 2 106 6 44 Spalart Allmaras turbulence model 2 125 species diffusivity UDFs 2 34 species mass fraction 2 31 2 114 species net reaction rate UDFs 2 50 specific dissipation Prandtl number UDFs 2 68 specific heat 2 87 specific heat UDFs 2 113 specular reflectivity UDFs 2 39 spray collide UDFs 2 194 SQR 2 122 2 126 3 82 storage checking 3 81 sub_domain_loop 3 60 sub_thread_loop 3 62 subdomains 1 17 subthreads 1 17 superdomains 1 17 superthreads 1 17 Surface Monitor dialog box 8 21 surface reaction rate 1 3 surface reaction rate UDFs 2 114 swirl center UDFs defining 2 211 hooking to ANSYS FLUENT 6 82 switching custom laws for DPM 2 196 Syamlal drag law 2 141 T_SAT 2 150 temperature equation diffusion Prandtl number UDFs 2 69 temperature limit UDFs NOx model 2 52 SOx model 2 106 temperature dependent viscosity 8 30 text editor 1 1 thermal conductivity 2 87 thermal wall function Prandtl number UDFs 2 70 Thread data structure 1 10 thread pointer 1 11 3 2 to array of phase threads 3 2 term Index 15 Index thread storage parallel 7 9 THREAD C0 2 168 THREAD F WALL 2 156 THREADD 2 115 2 117 2 177 thread_loop_c 2 9 2 18 2 168 3 56 thread_loop_f 2 168 3 56 THREAD_MATERIAL 2 90 2 92 2 177 2 197 THREAD SHADOW 3 35 THREAD_STORAGE 2 168 2 197 THREAD_SUB_THREAD 2 141 2 143 2 150 2 152 3 66 THREAD_SUB_THREADS 3 67 THREAD_
507. of each of the six particle laws e g First Law and click OK See Section 2 5 7 DEFINE_DPM_LAW for details about DEFINE_DPM_LAW functions Release 12 0 ANSYS Inc January 26 2009 6 71 Hooking UDFs to ANSYS FLUENT 6 4 8 Hooking DEFINE_DPM_OUTPUT UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_OUTPUT UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Sample Trajectories dialog box Figure 6 4 8 in ANSYS FLUENT In order to hook the UDF you must first set up the discrete phase model e g create a particle injection After you have run the calculation and generated data open the Sample Trajectories dialog box Figure 6 4 8 gt Reyes Bei Set Up Sample Trajectories Boundaries B B Lines B B Release From Injections 8 B axis A line 14 injection 1 coflow F default interior jet jet_wall jet_wall shadow outlet pilot pilot _wall pilot_wall shadow Fan lt a C Append Files Accumulate Erosion Accretion Rates User Defined Functions Output mv Figure 6 4 8 The Sample Trajectories Dialog Box Select the appropriate injection in the Release From Injections list indicate where the sample will be written e g make a selection in the Lines list and select the function name e g discrete phase_sample
508. of integer variables and integer variable arrays respectively PRF_GRSUM1 x computes the global sum of a real variable x across all compute nodes The global sum is of type float when running a single precision version of ANSYS FLUENT and type double when running the double precision version Alternatively PRF_GRSUM x N iwork computes the global sum of a float variable array for single precision and double when running double precision Global Summations Macro Action PRF_GISUM1 x Returns sum of integer x over all compute nodes PRF_GISUM x N iwork Sets x to contain sums over all compute nodes PRF_GRSUM1 x Returns sum of x over all compute nodes float if single precision double if double precision PRF_GRSUM x N iwork Sets x to contain sums over all compute nodes float array if single precision double array if double precision Global Maximums and Minimums Macros that can be used to compute global maximums and minimums of variables are identified by the suffixes HIGH and LOW respectively PRF_GIHIGH1 and PRF_GIHIGH com pute the global maximum of integer variables and integer variable arrays respectively PRF_GRHIGH1 x computes the global maximum of a real variable x across all compute nodes The value of the global maximum is of type float when running the single precision version of ANSYS FLUENT and type double when running the double precision version PRF_GRHIGH x N iwork computes the global maximum of a real v
509. of type UDF Source Files Figure 4 2 2 The Select File Dialog Box In the Select File dialog box select the desired file e g udfexample c and click OK The Select File dialog box will close and the complete path to the file you selected will appear in the Source File Name text box in the Interpreted UDFs dialog box Figure 4 2 1 In the Interpreted UDFs dialog box specify the C preprocessor to be used in the CPP Command Name text box You can keep the default cpp or you can enable the Use Contributed CPP option to use the preprocessor supplied by ANSYS FLUENT Keep the default Stack Size setting of 10000 unless the number of local vari ables in your function will cause the stack to overflow In this case set the Stack Size to a number that is greater than the number of local variables used Enable the Display Assembly Listing option on if you want a listing of assembly language code to appear in the console when the function interprets This option will be saved in your case file so that when you read the case in a subsequent ANSYS FLUENT session the assembly code will be automatically displayed e Click Interpret to interpret your UDF Release 12 0 ANSYS Inc January 26 2009 4 3 Common Errors Made While Interpreting A Source File If the compilation is successful and you have enabled Display Assembly Listing then the assembler code will be displayed in the console If you chose not to display the listin
510. ointer ip is pointing The use of pointers is demonstrated by the following int a 1 int ip ip amp a amp a returns the address of variable a printf content of address pointed to by ip d n ip xip 4 xa 4 printf now a d n a Here an integer variable a is initialized to 1 Next ip is declared as a pointer to an integer variable The address of variable a is then assigned to pointer ip Next the integer value of the address pointed to by ip is printed using ip This value is 1 The value of variable a is then indirectly set to 4 using ip The new value of a is then printed Pointers can also point to the beginning of an array and are strongly connected to arrays in C Pointers as Function Arguments C functions can access and modify their arguments through pointers In ANSYS FLUENT thread and domain pointers are common arguments to UDFs When you specify these arguments in your UDF the ANSYS FLUENT solver automatically passes data that the pointers are referencing to your UDF so that your function can access solver data You do not have to declare pointers that are passed as arguments to your UDF from the solver For example one of the arguments passed to a UDF that specifies a custom profile defined by the DEFINE_PROFILE macro is the pointer to the thread applied to by the boundary condition The DEFINE_PROFILE function accesses the data pointed to by the thread pointer Release 12 0 A
511. ointer to turbulent reaction rate Function returns void There are eight arguments to DEFINE_VR_RATE name c t r mw yi rr and rr_t You supply name the name of the UDF c t r mw yi rr and rr_t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to set the values referenced by the real pointers rr and rr_t to the laminar and turbulent reaction rates respectively rr and rr_t defined by the UDF are computed and the lower of the two values is used when the finite rate eddy dissipation chemical reaction mechanism used Note that rr and rr_t are conversion rates in kmol m s These rates when multiplied by the respec tive stoichiometric coefficients yield the production consumption rates of the individual chemical components Release 12 0 ANSYS Inc January 26 2009 2 1 29 DEFINE Macros Example 1 The following UDF named vol_reac_rate specifies a volume reaction rate The function must be executed as a compiled UDF in ANSYS FLUENT pE aaa o kkk kkk kk kk kkk kkk kkk kk kk kkk kkk kkk kk kk kkk k k k UDF for specifying a volume reaction rate The basics of ANSYS FLUENT s calculation of reaction rates only an Arrhenius finite rate reaction rate is calculated from the inputs given by the user in the graphical user interface EEEE ooo o kk kkk k kkk kkk kkk include udf h DEFINE_VR_RATE vol_reac_rate c t r wk yk rate rr_t real ci prod int i Calculate
512. ompile a UDF Using the TUI 8 In the architecture directory create directories named after the ANSYS FLUENT versions for which you want to build shared libraries e g ultra 2d and ultra 3qd Possible versions are 2d or 3d single precision serial 2D or 3D 2ddp or 3ddp double precision serial 2D or 3D 2d_node and 2d_host single precision parallel 2D 3d_node and 3d_host single precision parallel 3D 2ddp_node and 2ddp host double precision parallel 2D 3ddp_node and 3ddp_host double precision parallel 3D Note that you must create two build directories for each parallel version of the solver two for the 3D version two for the 2D double precision version etc regardless of the number of compute nodes 5 3 2 Build the UDF Library After you have set up the folder structure and put the files in the proper places you can compile and build the shared library using the TUI Windows Systems 1 Using a text editor edit every user_nt udf file in each version folder to set the following parameters SOURCES VERSION and PARALLEL_NODE SOURCES the user defined source file s to be compiled Use the prefix SRC before each filename For example SRC udfexample c for one file and SRC udfexamplel c SRC udfexample2 c for two files VERSION the version of the solver you are running which will be the name of the build folder where user_nt udf is located 2d 3d 2ddp 3ddp 2d_host 2d_node 3d_host 3d_node 2ddp_host 2ddp_no
513. ompiled Chapter 5 Com piling UDFs your DEFINE_MASS_TRANSFER UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Phase Interaction dialog box Figure 6 3 6 To hook the UDF to ANSYS FLUENT first make a selection from the Model list of the Multiphase Model dialog box A Dees Edit Next open the Phase Interaction dialog box Figure 6 3 6 lt EMEC gt Interaction Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Number of Mass Transfer Mechanisms 4 I J Mass Transfer From To Phase Species Phase Species Mechanism i p hase 1 M phase 1 2 K user defined v lig_gas_source libudf 7 Figure 6 3 6 The Phase Interaction Dialog Box Click the Mass tab and then specify the Number of Mass Transfer Mechanisms greater than 0 The Mechanism drop down list will appear Next select user defined from the Mechanism drop down list to open the User Defined Functions dialog box Figure 6 3 7 6 60 Release 12 0 ANSYS Inc January 26 2009 6 3 Hooking Multiphase UDFs User Defined Fu Hliq_gas_ source libudF lt EE Figure 6 3 7 The User Defined Functions Dialog Box Select the function name e g liq_gas_source udf and click OK The UDF name will appear in the text box below the Mechanism drop down list in the Phase Interaction dialog bo
514. ompiled into an intermediate architecture independent machine code using a C preprocessor This machine code then executes on an internal emulator or interpreter when the UDF is invoked This extra layer of code incurs a performance penalty but allows an interpreted UDF to be shared effortlessly between different architectures operating systems and ANSYS FLUENT versions If execution speed does become an issue an interpreted UDF can always be run in compiled mode without modification Release 12 0 ANSYS Inc January 26 2009 4 1 Interpreting UDFs 4 1 1 Location of the udf h File UDFs are defined using DEFINE macros see Chapter 2 DEFINE Macros and the defi nitions for DEFINE macros are included in udf h header file Consequently before you can interpret a UDF source file udf h will need to be accessible in your path or saved locally within your working folder The location of the udf h file is path ANSYS Inc v120 fluent fluent12 0 2 src udf h where path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and z is replaced by the appropriate number for the release e g 9 for fluent12 0 9 i In general you should not copy udf h from the installation area The compiler is designed to look for this file locally in your current folder first If it is not found in your current folder the compiler will look in the src folder automatically In the event that you upgra
515. ompt NO fuel NOx and N20 intermediate pathway That is a NO rate UDF can contain up to four separate rate functions that are concatenated in a single source file which you hook to ANSYS FLUENT DEFINE_NOX_RATE may also be used to calculate the upper limit for the integration of the temperature PDF when temperature is accounted for in the turbulence interaction mod eling You can calculate a custom maximum limit Tmax for each cell and then assign it to the POLLUT_CTMAX Pollut Par macro see Section 3 2 7 NO Macros for further details about data access macros Example 2 demonstrates this use of DEFINE NOX RATE If you want to use DEFINE NOX RATE only for the purpose of specifying Timax then be sure that the user defined NO rate does not alter the internally calculated rate for the source term calculation 2 52 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Usage DEFINE NOX RATE name c t Pollut Pollut Par NOx Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the NO rate is to be applied Pollut Cell Pollut Pointer to the data structure that contains the common data at each cell Pollut Parameter Pollut_Par Pointer to the data structure that contains auxiliary data NOx Parameter NOx Pointer to the data structure that contains data specific to the NO model Function returns void There are six arguments to DEF
516. on You can use DEFINE DOM DIFFUSE REFLECTIVITY to modify the inter facial reflectivity computed by ANSYS FLUENT at diffusely reflecting semi transparent walls based on the refractive index values During execution a DEFINE_DOM_DIFFUSE_REFLECTIVITY function is called by ANSYS FLUENT for each semi transparent wall and also for each band in the case of a non gray discrete ordinates DO model Therefore the function can be used to modify diffuse reflectivity and diffuse transmissivity values at the interface Usage DEFINE DOM DIFFUSE REFLECTIVITY name t nb n_a n_b diff_ref_a diff_tran_a diff_ref_b diff_tran_b Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Argument Type Description symbol name UDF name Thread t Pointer to the thread on which the discrete ordinate diffusivity function is to be applied int nb Band number needed for the non gray discrete ordinates DO model real na Refractive index of medium a real n_b Refractive index of medium b real diff_ref_a Diffuse reflectivity at the interface facing medium a real diff_tran_a Diffuse transmissivity at the interface facing medium a real diff_ref_b Diffuse reflectivity at the interface facing medium b real diff_tran_b Diffuse transmissivity at the interface facing medium b Function returns void There are nine argumen
517. on 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources This feature is not available in the GUI Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box describes how you can load and unload multiple UDF libraries using the UDF Library Manager dialog box The capability of loading more than one UDF library into ANSYS FLUENT raises the possibility of data contention if multiple libraries use the same user defined scalar UDS and user defined memory UDM locations These clashes can be avoided if libraries reserve UDS or UDM prior to usage See Sections 3 2 8 and 3 2 9 respectively for details e Section 5 1 Introduction e Section 5 2 Compiling a UDF Using the GUI e Section 5 3 Compile a UDF Using the TUI e Section 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources e Section 5 5 Load and Unload Libraries Using the UDF Library Manager Dialog Box e Section 5 6 Common Errors When Building and Loading a UDF Library e Section 5 7 Special Considerations for Parallel ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 5 1 Compiling UDFs 5 1 Introduction Compiled UDFs are built in the same way that the ANSYS FLUENT executable itself is built Internally a script called Makefile is used to invoke the system C compiler to build an object code library that contains the native machine language translation of your higher level C source code The object library is specific to th
518. on is occurring any extra heat flux that you add in a heat flux UDF can have a detrimental effect on the solution of the energy equation These effects will likely show up in conjugate heat transfer problems To avoid this you will need to make sure that your heat flux UDF excludes the walls adjacent to solids or includes only the necessary walls adjacent to fluid zones Usage DEFINE_HEAT_FLUX name f t c0 t0 cid cir Argument Type Description symbol name UDF name face_t f Index that identifies a wall face Thread t Pointer to wall face thread on which heat flux function is to be applied cell_t cO Cell index that identifies the cell next to the wall Thread t0O Pointer to the adjacent cell s thread real cid Array of fluid side diffusive heat transfer coefficients real cir Array of radiative heat transfer coefficients Function returns void There are seven arguments to DEFINE_HEAT_FLUX name f t c0 tO cid and cir You supply name the name of the UDF f t c0 and tO are variables that are passed by the ANSYS FLUENT solver to your UDF Arrays cir and cid contain the linearizations of the radiative and diffusive heat fluxes respectively computed by ANSYS FLUENT based on the activated models These arrays allow you to modify the heat flux in any Release 12 0 ANSYS Inc January 26 2009 2 45 DEFINE Macros way that you choose ANSYS FLUENT computes the heat flux at the wall using these arrays aft
519. on of state described in 1 The equations used in this UDRGM will be listed in the sections below The following nomenclature applies to this section Redlich Kwong temperature function speed of sound specific heat enthalpy exponent in function a T pressure universal gas constant molecular weight temperature entropy specific volume density Q 4 ee SHYT AOS l The superscript 0 designates a reference state and the subscript c designates a critical point property 8 48 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Specific Volume and Density The Redlich Kwong equation of state can be written in the following form RT a T 8 2 12 yeh V V b cae where i pat R27 V a T ao ao 0 42747 _ p T Pe RT RT bo 0 08664 gt C ao bo Ve b bo Co Pe Pe Vvet Since the real gas model in ANSYS FLUENT requires a function for density as a function of pressure and temperature Equation 8 2 12 must be solved for the specific volume from which the density can be easily obtained For convenience Equation 8 2 12 can be written as a cubic equation for specific volume as follows E T E 8 213 where T RTb T T b P P P P Equation 8 2 13 is solved using a standard algorithm for cubic equations see 10 for details In the UDRGM code the cubic solution is coded to minimize the number of floating point operatio
520. ons Continued Function DEFINE Macro Dialog Box Activated In wall thermal conditions heat flux heat generation rate temperature heat transfer coefficient external emissivity external radiation and free stream temperature wall radiation internal emissivity irradiation wall momentum shear stress x y z components swirl component moving wall velocity components roughness height roughness constant wall species mass fractions wall user defined scalar boundary value wall discrete phase boundary value density as function of temperature density as function of pressure for compressible liquids viscosity mass diffusivity thermal conductivity thermal diffusion coefficient DEF INE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Table 2 3 4 Quick Reference Guide for Model Specific DEFINE Functions Continued Function DEFINE Macro Dialog Box Activated In ab
521. onsult a C programming language manual for more details The format string for Message is similar to printf the standard C I O function see Section A 13 3 Standard I O Functions for details In the example below the text Volume integral of turbulent dissipation will be displayed in the console and the value of the replacement variable sum_diss will be substituted in the message for all instances of g Example Message Volume integral of turbulent dissipation g n sum_diss g represents floating point number in f or e format n denotes a new line i It is recommended that you use Message instead of printf in compiled UDFs UNIX only Release 12 0 ANSYS Inc January 26 2009 3 79 Additional Macros for Writing UDFs Error You can use Error when you want to stop execution of a UDF and print an error message to the console Example if table_file NULL Error error reading file i Error is not supported by the interpreter and can be used only in compiled UDFs 3 8 Miscellaneous Macros N_UDS You can use N_UDS to access the number of user defined scalar UDS transport equations that have been specified in ANSYS FLUENT The macro takes no arguments and returns the integer number of equations It is defined in models h N_UDM You can use N_UDM to access the number of user defined memory UDM locations that have been used in ANSYS FLUENT The macro takes no arguments and returns th
522. ontinuous Phase _ Unsteady Particle Tracking Tracking Physical Models UDF Numerics Parallel Tracking Parameters Drag Parameters Max Number of Steps Drag Law a zae 500 5 dF particle_drag_force libudF Specify Length Scale Length Scale m 0 01 Figure 6 4 3 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the Tracking tab in the Discrete Phase Model dialog box Select the function name e g particle drag_force libudf from the Drag Law drop down list in the Drag Pa rameters group box Figure 6 4 3 and click OK Note that function names listed in the drop down list are preceded by the word udf as in udf particle_ drag_force libudf See Section 2 5 3 DEFINE_DPM_DRAG for details about DEFINE_DPM_DRAG functions 6 66 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs 6 4 4 Hooking DEFINE_DPM_EROSION UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_EROSION UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Discrete Phase Model dialog box Figure 6 4 4 in ANSYS FLUENT To hook the UDF first open the Discrete Phase Model dialog box Vere DEZA Edit Discrete Phase Mode
523. op down list in the Create Edit Materials dialog box This will open the User Defined Functions dialog box Release 12 0 ANSYS Inc January 26 2009 6 23 Hooking UDFs to ANSYS FLUENT where you must select the name of the function e g user_gray_band_abs libudf and click OK Finally click Change Create in the Create Edit Materials dialog box See Section 23 8 DEFINE GRAY BAND ABS COEFF for details about DEFINE GRAY BAND ABS COEFF functions 6 2 9 Hooking DEFINE HEAT FLUX UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_HEAT_FLUX UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 11 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 11 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Figure 6 2 11 The User Defined Function Hooks Dialog Box i The Energy Equation must be enabled Select the function name e g user_heat_flux libudf in the Wall Heat Flux drop down list in the User Defined Function Hooks dialog box and click OK
524. op down list of the Create Edit Materials dialog box Figure 6 2 3 The User Defined Functions dialog box Figure 6 2 4 will open 6 16 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs User Defined Fu mean age diff libudf Figure 6 2 4 The User Defined Functions Dialog Box Select the name of your UDF e g mean_age_diff libudf and click OK in the User Defined Functions dialog box The name will then be displayed in the field below the Mass Diffusivity drop down list in the Create Edit Materials dialog box Click Change Create to save your settings e To hook a single diffusion coefficient UDF so that it applies to all UDS equations first set the number and options of the user defined scalars using the User Defined Scalars dialog box Define User Defined Scalars Then select user defined from the UDS Diffusivity drop down list in the Create Edit Materials dialog box Figure 6 2 5 Next select the name of your UDF e g mean_age_diff libudf in the User Defined Functions dialog box that opens Figure 6 2 4 and click OK The name will then be displayed in the field below the UDS Diffusivity drop down list in the Create Edit Materials dialog box Click Change Create to save your settings See Section 2 3 3 DEFINE_DIFFUSIVITY for details about defining DEFINE_DIFFUSIVITY UDFs and the User s Guide for general information about UDS diffusivit
525. open the Discrete Phase Model dialog box eee beer Edit Discrete Phase Model Interaction Particle Treatment Interaction with Continuous Phase Unsteady Particle Tracking k with Fl ow Time Step C Update DPM Sources Every Flow Iteration Tract Number of Continuous Phase 10 a Inject Particles at Iterations per DPM Iteration ice Particle Time Step Fluid Flow Time Step Particle Time Step Size 5s 0 001 Number of Time Steps 4 g Clear Particles Tracking Physical Models UDF Numerics Parallel User Defined Functions User variables Body Force Number of Scalars a none v 0 5 Scalar Update hone J Source none v Spray Collide Function mempen v DPM Time Step none v Figure 6 4 13 The Discrete Phase Model Dialog Box Click the Injections button to open the Injections dialog box Create an injection and then click Close in the Injections dialog box Next click the Physical Models tab in the Discrete Phase Model dialog box and enable the Droplet Collision option in the Spray Model group box Then click the UDF tab and Release 12 0 ANSYS Inc January 26 2009 6 77 Hooking UDFs to ANSYS FLUENT select the function name e g mean_spray_collide libudf from the Spray Collide Function drop down list in the User Defined Functions group box Figure 6 4 3 and click OK See Section 2 5 12 DEFINE DPM SPRAY _COLLIDE for details abo
526. or The identifiers correspond to the phases you select in the Phase Interaction dialog box in the graphical user interface An index of 0 corresponds to the primary phase and is incremented by one for each secondary phase int first_column_phase_index See int second_column_phase_index Function returns real 2 1 40 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros There are five arguments to DEFINE_EXCHANGE_PROPERTY name c mixture_thread second_column_phase_index and first_column_phase_index You supply name the name of the UDF c mixture_thread second_column_phase_index and first_column phase_index are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value of the lift coefficient drag exchange coefficient heat or mass transfer to the solver Example 1 Custom Drag Law The following UDF named custom_drag can be used to customize the default Syamlal drag law in ANSYS FLUENT The default drag law uses 0 8 for void lt 0 85 and 2 65 void gt 0 85 for bfac This results in a minimum fluid velocity of 25 cm s The UDF modifies the drag law to result in a minimum fluid velocity of 8 cm s using 0 28 and 9 07 for the bfac parameters DCR RR RK 2K 2K K FK aK FK FK 2k K 2k 6 2k K 2k ak UDF for customizing the default Syamlal drag law in ANSYS FLUENT BER AAR RI I I I OKRA A A A A 21 KK KEK KEK A AK A A A KK KK kkk kk k kkk k include
527. or boundary faces e g wall zones your UDF will also need to calculate interior face values from the cell values of adjacent cells This is most easily done using the arithmetic mean method Vector arithmetic can be coded in C using the NV_ and ND_ macros see Chapter 3 Additional Macros for Writing UDFs Note that if you had to implement the default advection term in a UDF without the fluid density in the definition of y see above you could simply put the following line in your DEFINE_UDS_FLUX UDF return F_FLUX f t rho where the denominator p can be determined by averaging the adjacent cell s density values C_R F_CO f t THREAD_TO t and C_R F_C1 f t THREAD_T1 t Example The following UDF named my_uds_f1lux returns the mass flow rate through a given face The flux is usually available through the ANSYS FLUENT supplied macro F_FLUX t Section 3 2 4 Face Macros The sign of flux that is computed by the ANSYS FLUENT solver is positive if the flow direction is the same as the face area normal direction as determined by F_AREA see Section 3 2 4 Face Area Vector F_AREA and is negative if the flow direction and the face area normal directions are opposite By convention face area normals always point out of the domain for boundary faces and they point in the direction from cell cO to cell c1 for interior faces The UDF must be executed as a compiled UDF 2 232 Release 12 0 ANSYS Inc January 26 2009
528. or every user defined scalar that you allo cate in the graphical user interface For example if you specify 2 as the Number of User Defined Scalars then two variables with default names User Scalar 0 and User Scalar 1 will be defined and the variables with these default names will appear in setup and postprocessing dialog boxes You can change the default names if you wish using Set_User_Scalar_Name as described below The default name that appears in the graphical user interface and on plots in ANSYS FLUENT for user defined scalars e g User Scalar 0 can now be changed using the function Set_User_Scalar_Name void Set_User_Scalar_Name int i char name i is the index of the scalar and name is a string containing the name you wish to assign It is defined in sg_udms h Set_User_Scalar_Name should be used only once and is best used in an EXECUTE_ON_LOADING UDF see Section 2 2 6 DEFINE_EXECUTE_ON_LOADING Due to the mechanism used UDS variables cannot be renamed after they have been set so if the name is changed in a UDF for example and the UDF library is reloaded then the old name could remain In this case restart ANSYS FLUENT and load the library again 3 44 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros F_UDSI You can use F_LUDSI when you want to access face variables that are computed for user defined scalar transport equations Table 3 2 35 See Section 3 2 9 Example UDF that Utilizes UDM
529. orce on a particle and is a variation of the body force UDF presented in Section 2 5 2 DEFINE_DPM_BODY_FORCE The flow is the same but a different curve is used to describe the particle drag DEFINE_DPM_DRAG is called at every particle time step in ANSYS FLUENT and requires a significant amount of CPU time to execute For this reason the UDF should be executed as a compiled UDF DORA OGG AAA AA AAA AK a aC KCK UDF for computing particle drag coefficient 18 Cd Re 24 curve as suggested by R Clift J R Grace and M E Weber Bubbles Drops and Particles 1978 AOA AAO AAA AAA AIR A aK KKK a include udf h DEFINE_DPM_DRAG particle_drag_force Re p real w drag_force if Re lt 0 01 drag_force 18 0 return drag_force else if Re lt 20 0 w log10 Re drag_force 18 0 2 367 pow Re 0 82 0 05 w return drag_force else Note suggested valid range 20 lt Re lt 260 2 1 66 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros drag_force 18 0 3 483 pow Re 0 6305 return drag_force Hooking a DPM Drag Coefficient UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_DRAG is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model dialog box in ANSYS FLUE
530. os for Writing UDFs for details Every UDF must contain the udf h file inclusion directive include udf h at the beginning of the source code file which allows definitions of DEFINE macros and other ANSYS FLUENT provided macros and functions to be included during the compilation process See Section 1 4 1 Including the udf h Header File in Your Source File for details Note that values that are passed to a solver by a UDF or returned by the solver to a UDF are specified in SI units Source files containing UDFs can be either interpreted or compiled in ANSYS FLUENT For interpreted UDFs source files are interpreted and loaded directly at runtime in a single step process For compiled UDFs the process involves two separate steps A shared object code library is first built and then it is loaded into ANSYS FLUENT See Chapter 4 Interpreting UDFs and Chapter 5 Compiling UDFs After being interpreted or compiled UDFs will become visible and selectable in ANSYS FLUENT dialog boxes and can be hooked to a solver by choosing the function name in the appropriate dialog box This process is described in Chapter 6 Hooking UDFs to ANSYS FLUENT In summary UDFs e are written in the C programming language Appendix A e must have an include statement for the udf h file Section 1 4 1 Including the udf h Header File in Your Source File e must be defined using DEFINE macros supplied by ANSYS FLUENT Chapter 2 DEFINE Macros e utilize pr
531. ou to hook the function to your model Note that the UDF name you supply cannot contain a number as the first character The equation that is defined by the function will be applied to all cell faces identified by f in the face loop on a given boundary zone identified by thread The thread is defined automatically when you hook the UDF to a particular boundary in the ANSYS FLUENT GUI The index is defined automatically through the begin_f_loop utility In this UDF the begin f_loop macro Section 3 3 Looping Macros is used to loop through all cell faces in the boundary zone For each face the coordinates of the face centroid are accessed by F_CENTROID Section 3 2 4 Face Centroid F_CENTROID The y coordinate y is used in the parabolic profile equation and the returned velocity is assigned to the face through F_PROFILE begin f_loop and F_PROFILE Section 3 2 6 Set Boundary Condition Value F_PROFILE are ANSYS FLUENT supplied macros Refer to Chapter 3 Additional Macros for Writing UDFs for details on how to utilize predefined macros and functions supplied by ANSYS FLUENT to access ANSYS FLUENT solver data and perform other tasks 8 1 4 Step 3 Start ANSYS FLUENT and Read or Set Up the Case File After you have created the source code for your UDF you are ready to begin the problem setup in ANSYS FLUENT 1 Start ANSYS FLUENT in Windows using FLUENT Launcher with the following settings e Specify the folder that contains your case
532. our UDF Input arguments belong to the following ANSYS FLUENT data types Node node pointer to a node cellt c cell identifier facet f face identifier Thread t pointer to a thread Thread pt pointer to an array of phase threads Below is an example of a UDF that assigns initial temperature which utilizes two data access macros C_T and C_CENTROID and two looping macros begin end_c_loop_all and thread_loop_c Two looping macros are used to set the cell temperature of each cell in every thread in the computational domain begin end_c_loop_all is used to loop over all the cells in a cell thread to get the cell centroid and set the cell temperature and thread_loop_c allows this loop to be repeated over all cell threads in the domain C_CENTROID has three arguments xc c and t Cell identifier c and cell thread pointer t are input arguments and the argument array xc the cell centroid is output as an argument to the solver and used in the UDF in a conditional test 3 2 Release 12 0 ANSYS Inc January 26 2009 3 1 Introduction C_T is used to set the cell temperature to the value of 400 or 300 depending on the outcome of the conditional test It is passed the cell s ID c and thread pointer t and returns the real value of the cell temperature to the ANSYS FLUENT solver Example POR CAO AA AAR I I kk kkk kkk kkk kk kk kkk k k 4 24 k UDF for initializing flow field variables Example of C_T and C_CENTROID usage BO
533. p vfact4 8 sqrt vfac vfac 2 24 0 k_g_s 1 void_g rho_s fdrgs taup return k_gs 2 1 42 Release 12 0 ANSYS Inc January 26 2009 2 4 Multiphase DEF INE Macros Example 2 Heat Transfer The following UDF named heat_udf specifies a coefficient that when multiplied by the temperature difference between the dispersed and continuous phases is equal to the net rate of heat transfer per unit volume include udf h define PR_NUMBER cp mu k cp mu k define IP_HEAT_COEFF vof k nu d vof 6 k Nu d d static real heat_ranz_marshall cell_t c Thread ti Thread tj real h real d C_PHASE_DIAMETER c tj real k C_K_L c ti real NV_VEC v vel Re Pr Nu NV_DD v C_U c tj C_V c tj C_W c tj C_U c ti C_V c ti C_W c ti vel NV_MAG v Re RE_NUMBER C_R c ti vel d C_MU_L c ti Pr PR_NUMBER C_CP c ti C_MU_L c ti k Nu 2 0 6 sqrt Re pow Pr 1 3 h IP_HEAT_COEFF C_VOF c tj k Nu d return h DEFINE_EXCHANGE_PROPERTY heat_udf c t i j Thread ti THREAD_SUB_THREAD t i Thread tj THREAD_SUB_THREAD t j real val val heat_ranz_marshall c ti tj return val Release 12 0 ANSYS Inc January 26 2009 2 1 43 DEFINE Macros Hooking an Exchange Property UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_ EXCHANGE_PROPERTY is interpreted Chapter 4 Interpreting UDFs or compiled Chapter
534. p 2 Create a C Source File 2 aora ee ee 8 4 8 1 4 Step 3 Start ANSYS FLUENT and Read or Set Up the Case File os a ppe aa be oe e ee Sw ee 8 5 8 1 5 Step 4 Interpret or Compile the Source File 8 6 8 1 6 Step 5 Hook the UDF to ANSYS FLUENT 8 11 8 1 7 Step 6 Rum the Calculation s ec scet adadi te 544244 8 12 8 1 8 Step 7 Analyze the Numerical Solution and Compare to Expected Results 4 Roe sc nea eee ba ee hewn eee ees 8 12 Release 12 0 ANSYS Inc January 26 2009 IX CONTENTS 8 2 Detailed UDF Examples seoran 44244 44 wee KY wee ee eS 8 13 g2 1 Boundary Conditions se s lt e soe s momia e wba ead O42 8 14 8 2 2 Source Tetms a wc ewe erissa pr kA ke ya g 8 25 8 2 3 Physical Properties 42450484 a siei Sa gie D ani s 8 30 8 24 Reaction Rates 2 28 sesi p ae SR bee ee ee E a oe CaS 8 35 8 2 5 User Defined Scalars 2 aa ee 8 40 8 2 6 User Defined Real Gas Models 8 48 A C Programming Basics A 1 A1 Introduction seresa sd sraid ESR OE EH OR EEG HESS A 1 A2 Commenting your Code e seq cs sat 6 YR RY we KON So A 2 A3 C Data Types in ANSYS FLUENT ea 3 ee ae Blew ORR i HRS A 2 AA Constants sao ara ae dai OH we ER ee Ee oo A e A 3 AD Varnables orama Aaea EE eG ARS OE Oe oO ERO a A 3 A 5 1 Declaring Variables 68 bso deo we eee eR we HES A 4 A 5 2 External Variables 2 42 40 4 0 one A EE ER Se ER eS ERS A 4 Ae Static Variables s se koe 24 Sho Ma who ea baw OH ASS A
535. p and ci are variables that are passed by the ANSYS FLUENT solver to your UDF Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Release 12 0 ANSYS Inc January 26 2009 2 1 81 DEFINE Macros Example The following UDF named Evapor_Swelling Law models a custom law for the evapo ration swelling of particles The source code can be interpreted or compiled in ANSYS FLUENT See Section 2 5 13 Example for another example of DEFINE_DPM_LAW usage DOR OO OO I RI FK FK 2K 2K FK 2K 2K K 2K 2K K 2k 2 K 2k 2K 2k K 2k 2K 2k K 2k 2k K 2k 2k 2k UDF that models a custom law for evaporation swelling of particles EEEE ooo ooo ooo kkk kk kkk kkk kkk include udf h DEFINE_DPM_LAW Evapor_Swelling_Law p ci real swelling_coeff 1 1 first call standard evaporation routine to calculate the mass and heat transfer VaporizationLaw p compute new particle diameter and density P_DIAM p P_INIT_DIAM p 1 swelling coeff 1 P_INIT_MASS p P_MASS p DPM_VOLATILE_FRACTION p P_INIT_MASS p P_RHO p P_MASS p 3 14159 P_DIAM p P_DIAM p P_DIAM p 6 P_RHO p MAX 0 1 MIN 1e5 P_RHO p J Hooking a Custom DPM Law to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_LAW is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling
536. p cell thread humidity myHumidity cell thread min MIN min humidity max MAX max humidity C_UDMI cell thread UDM_RH humidity end_c_loop cell thread J Message nRelative Humidity set in udm d UDM_RH Message range f 7 f n min max end if for enough UDSs and UDMs DEFINE_ON_DEMAND set_relhum adj_relhum Get_Domain 1 Hooking a DPM Switching UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_SWITCH is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become vis ible in the Custom Laws dialog box in ANSYS FLUENT See Section 6 4 13 Hooking DEFINE_DPM_SWITCH UDFs for details on how to hook your DEFINE_DPM_SWITCH UDF to ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 2 201 DEFINE Macros 2 5 14 DEFINE_DPM_TIMESTEP Description You can use DEFINE DPM TIMESTEP to change the time step for DPM particle tracking based on user specified inputs The time step can be prescribed for special applications where a certain time step is needed It can also be limited to values that are required to validate physical models Usage DEFINE DPM TIMESTEP name p ts Argument Type Description symbol name UDF name Tracked Particle p Pointer to the Tracked Particle data structure which contains data related to the particle being tracked real
537. p_dot is the positive mass source to the continuous phase Difference in mass between entry and exit from cell multiplied by strength Number of particles s in stream mp_dot P_MASSO p P_MASS p strength C_DPMS_YI c t 0 mp_dot dpm_relax C_DPMS_ENERGY c t mp_dot dpm_relax MATERIAL_PROP sp PROP_Cp C_T c t 298 15 C_DPMS_ENERGY c t mp_dot dpm_relax MATERIAL_PROP sp PROP_latent_heat define UDM_RH O define N_REQ_UDM 1 define CONDENS_LIMIT 1 0e 10 DEFINE_DPM_SWITCH dpm_switch p coupled cell_t c P_CELL p Thread t P_CELL_THREAD p if C_UDMI c t UDM_RH gt 1 0 P_CURRENT_LAW p DPM_LAW_USER_1 else if P_MASS p lt CONDENS_LIMIT P_CURRENT_LAW p DPM_LAW_INITIAL_INERT_HEATING else P_CURRENT_LAW p DPM_LAW_VAPORIZATION DEFINE_ADJUST adj_relhum domain cell_t cell Thread thread set dpm source underrelaxation 2 200 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros dpm_relax Domainvar_Get_Real ROOT_DOMAIN_ID dpm relax if sg_udm lt N_REQ_UDM Message nNot enough user defined memory allocated d required n N_REQ_UDM else real humidity min max min 1e10 max 0 0 thread_loop_c thread domain Check if thread is a Fluid thread and has UDMs set up on it if FLUID_THREAD_P thread amp amp NNULLP THREAD_STORAGE thread SV_UDM_I begin_c_loo
538. para h for definition of this loop PRF_CRECV_INT i amp n_faces 1 i n_faces now value for node i Reallocate memory for arrays for node i p_array real realloc p_array n_faces xsizeof real x_array real ND_ND realloc x_array ND_ND n_faces sizeof real Receive data PRF_CRECV_REAL i p_array n_faces i PRF_CRECV_REAL i x_array 0 ND_ND n_faces i for j 0 j lt n_faces j if RP_3D Message0 12 4e 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 x_array j 2 p_arrayl j else 2D Message0 12 4e 12 4e 12 4e n x_array j 0 x_array j 1 p_array j endif endif RP_NODE free p_array Each array has to be freed before function exit free x_array endif RP_HOST 7 32 Release 12 0 ANSYS Inc January 26 2009 7 6 Limitations of Parallel UDFs 7 5 9 Macros for Exchanging Data Between Compute Nodes EXCHANGE_SVAR_MESSAGE and EXCHANGE_SVAR_FACE_MESSAGE can be used to exchange storage variables SV_ between compute nodes EXCHANGE_SVAR_MESSAGE exchanges cell data between compute nodes while EXCHANGE_SVAR_FACE_MESSAGE exchanges face data Note that compute nodes are virtually synchronized when an EXCHANGE macro is used receiving compute nodes wait for data to be sent before continuing Compute Node Exchange Macros EXCHANGE_SVAR_FACE_MESSAGE domain SV_P SV_NULL EXCHANGE_SVAR_MESSAGE domain
539. particle mixture material int nc TP_N_COMPONENTS p number of particle components real Tp P_T p particle temperature real molwt_cond 0 reciprocal molecular weight of the particle for is 0 is lt nc ist int gas_index TP_COMPONENT_INDEX_I p is index of vaporizing component in the gas phase if gas_index gt 0 the molecular weight of particle material molwt gas_index MATERIAL_PROP MIXTURE_COMPONENT gas_mix gas_index PROP_mwi molwt_cond TP_COMPONENT_I p is molwt gas_index prevent division by zero molwt_cond MAX molwt_cond DPM_SMALL for is 0 is lt nc is gas species index of vaporization int gas_index TP_COMPONENT_INDEX_I p is if gas_index gt 0 condensed material Material cond_c MIXTURE_COMPONENT cond_mix is condensed component molefraction 2 206 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros real xi_cond TP_COMPONENT_I p is molwt gas_index molwt_cond particle saturation pressure real p_saturation DPM_vapor_pressure p cond_c Tp if p_saturation lt 0 0 p_saturation 0 0 vapor pressure over the surface this is the actual Raoult law cvap_surf is xi_cond p_saturation UNIVERSAL_GAS_CONSTANT Tp compressibility for ideal gas Z 1 0 J Hooking a DPM Vapor Equilibrium UDF to ANSYS FLU
540. particle time P_DT p Tracked_Particle p time step P_FLOW_ RATE p Tracked_Particle p flow rate of particles in a stream in kg s see below for details P_LF p Tracked_Particle p liquid fraction wet combusting particles only P_VFF p Tracked Particle p volatile fraction combusting particles only 3 36 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros P_FLOW_RATE p Each particle in a steady flow calculation represents a stream of many particles that follow the same path The number of particles in this stream that passes a particular point in a second is the strength of the stream P_FLOW_RATE returns the strength multiplied by P_MASS p at the current particle position Table 3 2 27 Macros for Particles at Entry to Current Cell Defined in dpm h Macro Argument Types Returns P_POSO p i P_VELO p i P_DIAMO p P_TO p P_RHOO p P_MASSO p P_TIMEO p P_LFO p Tracked Particle Tracked Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle Tracked_Particle p int i p int i p p p p p p position i 0 1 2 velocity i 0 1 2 diameter temperature density mass particle time at entry liquid fraction wet combusting particles only Note that when you are the using the macros listed in Table 3 2 27 to track transient particles the particle state is the beginning of the fluid flow time step
541. path in the Win 32 text box or click to browse for a batch file 5 4 Release 12 0 ANSYS Inc January 26 2009 5 2 Compiling a UDF Using the GUI By default the FLUENT Launcher dialog box is set to use udf bat file that is that is saved in your computer as part of the ANSYS FLUENT installation It is recommended that you keep the default batch file which is tested with the latest MS Visual Studio C compilers at the time of the ANSYS FLUENT release date 5 2 Compiling a UDF Using the GUI The general procedure for compiling a UDF source file and building a shared library for the resulting objects and loading the compiled UDF library into ANSYS FLUENT using the graphical user interface GUI is as follows i Note that in order to compile a UDF when running serial or parallel AN SYS FLUENT on a Windows system then you must have Microsoft Visual Studio installed on your machine preferably on the C drive 1 Make sure that the UDF source file you want to compile is in the same folder that contains your case and data files i Note that if you wish to compile a UDF while running ANSYS FLUENT on a Windows parallel network then you must share the working folder where the UDF is located so that all computers on the cluster can see this folder To share the working folder open Windows Explorer and browse to the folder right click on the working folder select Sharing and Security from the menu click Share this folder and cl
542. pdT Release 12 0 ANSYS Inc January 26 2009 8 89 Examples FUNCTION RKEOS_Cp_ideal_gas Returns ideal gas specific heat given T 7 7 eee double RKEOS_Cp_ideal_gas double temp int i double cpi cp 0 i temp cp 1 i temp cp 2 i temp cp 3 i temp cp 4 i if cpi lt SMLL cpi 1 0 return cpi FUNCTION RKEOS_H_ideal_gas Returns ideal gas specific enthalpy given T double RKEOS_H_ideal_gas double temp int i double h temp cp 0 Li temp 0 5 cp 1 i temp 0 333333 cp 2 i temp 0 25 cp 3 i temp 0 2 cp 4 i if h lt SMLL h 1 0 return h FUNCTION RKEOS_vol_specific_heat Returns constant volume specific heat given T and rho double RKEOS_vol_specific_heat double temp double density int i double afun a0 i pow tcrit i temp nrk i double v 1 density double Cv0 RKEOS_Cp_ideal_gas temp i rgas i int npi ark i 1 b0 i if Cv0 lt SMLL CvO 1 return CvO nrk i np1i afun log 1 0 b0 i v temp 8 90 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples FUNCTION RKEOS_
543. pecify The first argument is the format string It specifies how the remaining arguments are to be displayed in the console The format string is defined within quotes The value of the replacement variables that follow the format string will be substituted in the display for all instances of Ztype The character is used to designate the character type Some common format characters are d for integers f for floating point numbers and e for floating point numbers in exponential format with e before the exponent The format string for printf is the same as for fprintf and fscanf In the example below the text Content of variable a is will be displayed in the console and the value of the replacement variable a will be substituted in the message for all instances of d Example int a 5 printf Content of variable a is d n a n denotes a new line i UNIX only It is recommended that you use the ANSYS FLUENT Message utility instead of printf for compiled UDFs See Section 3 7 Message for details on the Message macro fprintf int fprintf FILE fp char format The function fprintf writes to a file that is pointed to by fp in a format that you specify The first argument is the format string It specifies how the remaining arguments are to be written to the file The format string for fprintf is the same as for printf and fscanf Release 12 0 ANSYS Inc January 26 2009 A 15 C Programming Basics
544. perature granular flux granular temperature user scalar boundary value discrete phase boundary value species boundary condition DEF INE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEF INE_PROFILE DEFINE_PROFILE DEF INE_PROFILE DEFINE_PROFILE DEFINE _DPM_BC DEFINE_PROFILE mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture mixture secondary phase s secondary phase s mixture mixture phase dependent Release 12 0 ANSYS Inc January 26 2009 C 3 Eulerian Model Laminar Flow Table C 2 3 DEFINE Macro Usage for the Mixture Model Variable Macro Phase Specified On Material Properties cavitation surface tension coefficient cavitation vaporization pressure particle or droplet diameter granular diameter granular solids pressure granular radial distribution granular elasticity modulus granular viscosity granular temperature DEF INE_PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY phase interaction phase interaction secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s Other slip velocity drag coefficient mass transfer coefficient heterog
545. perbolic cosine of x double sinh double x returns the hyperbolic sine of x double tanh double x returns the hyperbolic tangent of x A 13 2 Miscellaneous Mathematical Functions The C functions shown on the left below correspond to the mathematical functions shown on the right double sqrt double x yT double pow double x double y x double exp double x e7 double log double x ln x double log10 double x logio x double fabs double x z double ceil double x smallest integer not less than x double floor double x largest integer not greater than x Release 12 0 ANSYS Inc January 26 2009 A 13 C Programming Basics A 13 3 Standard I O Functions A number of standard input and output I O functions are available in C and in ANSYS FLUENT They are listed below All of the functions work on a specified file except for printf which displays information that is specified in the argument of the function The format string argument is the same for printf fprintf and fscanf Note that all of these standard C I O functions are supported by the interpreter so you can use them in either interpreted or compiled UDFs For more information about standard I O functions in C you should consult a reference guide e g 6 Common C I O Functions fopen filename mode opens a file fclose fp closes a file printf format formatted print to the console fprintf fp format formatt
546. piling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my_init_func will become visible and selectable via the User Defined Function Hooks dialog box in ANSYS FLUENT Note that you can hook multiple init functions to your model See Section 6 1 5 Hooking DEFINE_INIT UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 19 DEFINE Macros 2 2 9 DEFINE_ON_DEMAND Description DEFINE_ON_DEMAND is a general purpose macro that you can use to specify a UDF that is executed on demand in ANSYS FLUENT rather than having ANSYS FLUENT call it automatically during the calculation Your UDF will be executed immediately after it is activated but it is not accessible while the solver is iterating Note that the domain pointer d is not explicitly passed as an argument to DEFINE_ON_DEMAND Therefore if you want to use the domain variable in your on demand function you will need to first retrieve it using the Get_Domain utility provided by ANSYS FLUENT shown in the example below See Section 3 2 6 Domain Pointer Get_Domain for details on Get_Domain Usage DEF INE_ON_DEMAND name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE_ON_DEMAND name You supply name the name of the UDF Example The following UDF named on_demand_calc computes and prints the minimum maxi mum and average temperatures for the current dat
547. ples of UDFs that can be used to customize user defined scalar UDS transport equations See Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros in the UDF Manual for information on how you can define UDFs in ANSYS FLUENT See Section 1 3 User Defined Scalar UDS Transport Equations in the separate Theory Guide for UDS equation theory and details on how to set up scalar equations Postprocessing Using User Defined Scalars Below is an example of a compiled UDF that computes the gradient of temperature to the fourth power and stores its magnitude in a user defined scalar The computed tem perature gradient can for example be subsequently used to plot contours Although the practical application of this UDF is questionable its purpose here is to show the method ology of computing gradients of arbitrary quantities that can be used for postprocessing RTT CC CCL OL ICLoLrreCrrrr recor er error ererrorerrrrerrorrererrrerrre rere UDF for computing the magnitude of the gradient of T74 VEEEEEEEEEEEEEEEEEEEEEEEEE EEEE EEEE include udf h 8 40 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Define which user defined scalars to use enum T4 MAG_GRAD_T4 N_REQUIRED_UDS DEFINE_ADJUST adjust_fcn domain Thread t cell_t c face_t f Make sure there are enough user defined scalars if n_uds lt N_REQUIRED_UDS Internal_Error not enough user defined
548. pressure temperature turbulence kinetic energy turbulence dissipation rate e mass flux e target mass flow rate as a function of physical flow time e species mass fraction species transport e volume fraction multiphase models e wall thermal conditions temperature heat flux heat generation rate heat transfer coefficients and external emissivity etc e wall roughness conditions e wall shear and stress conditions e porosity e porous resistance direction vector e wall adhesion contact angle VOF multiphase model Note that DEFINE_PROFILE allows you to modify only a single value for wall heat flux Sin gle values are used in the explicit source term which ANSYS FLUENT does not linearize If you want to linearize your source term for wall heat flux and account for conductive and radiative heat transfer separately you will need to use DEFINE_HEAT_FLUX to specify your UDF Some examples of boundary profile UDFs are provided below For an overview of the ANSYS FLUENT solution process which shows when a DEFINE_PROFILE UDF is called refer to Figures 1 9 1 1 9 2 and 1 9 3 2 72 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Usage DEFINE _PROFILE name t i Argument Type Description symbol name UDF name Thread t Pointer to thread on which boundary condition is to be applied int i Index that identifies the variable that is to be defined i is set when you hook the UDF with
549. propriate material from the Material selection list and click the Create Edit button to open the Create Edit Materials dialog box Figure 6 2 22 6 38 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs Create Edit Materials Name air Material Type fluid Chemical Formula fi era Properties Absorption Coefficient 1 m Sa FLUENT Fluid Materials lair 0 Scattering Coefficient 1 m defined ScatPhiB2 Scattering Phase Function isotropic Refractive Index constant 1 Order Materials by l Name 1 Chemical Formula E __FLUENT Database User Defined Database v Figure 6 2 22 The Create Edit Materials Dialog Box Open the User Defined Functions dialog box Figure 6 2 23 from the Create Edit Material dialog box by selecting user defined in the drop down list for the Scattering Phase Function property Then select the function name e g ScatPhiB2 from the list of UDFs displayed in the User Defined Functions dialog box and click OK The name of the function will subsequently be displayed under the Scattering Phase Function property in the Create Edit Materials dialog box Release 12 0 ANSYS Inc January 26 2009 6 39 Hooking UDFs to ANSYS FLUENT User Defined Fu Scat PhB ScatPhiB1 ScatPhiF3 ScatPhiF2 ScatIso Figure 6 2 23 The User Def
550. pter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT whenever the Compo sition PDF Transport model is enabled See Section 6 2 2 Hooking DEFINE_CPHI UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 33 DEFINE Macros 2 3 3 DEFINE DIFFUSIVITY Description You can use DEFINE DIFFUSIVITY to specify the diffusivity for the species transport equations e g mass diffusivity or for user defined scalar UDS transport equations For details about UDS diffusivity see Section 8 6 User Defined Scalar UDS Diffusivity in the separate User s Guide Usage DEFINE DIFFUSIVITY name c t i Argument Type Description symbol name UDF name cellt c Cell index Thread t Pointer to cell thread on which the diffusivity function is to be applied int i Index that identifies the species or user defined scalar Function returns real There are four arguments to DEFINE_DIFFUSIVITY name c and t and i You supply name the name of the UDF c t and i are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the diffusivity only for a single cell and return the real value to the solver Note that diffusivity UDFs are called by ANSYS FLUENT from within a loop on cell threads Consequently your UDF will not need to loop over cells in a th
551. ptions UDS Index a Gls Solution Zones all Fluid zones v Flux Function iny uds flux slibudF v Figure 6 6 3 The User Defined Scalars Dialog Box To hook the UDF to ANSYS FLUENT first specify the Number of User Defined Scalars e g 2 in the User Defined Scalars dialog box Figure 6 6 3 As you enter the number of user defined scalars the dialog box will expand to show the User Defined Scalars Options group box Next for each scalar you have defined increment the UDS Index and select the Solution Zones e g all fluid zones and the name of the function e g my uds flux libudf from the Flux Function drop down list and click OK Release 12 0 ANSYS Inc January 26 2009 6 93 Hooking UDFs to ANSYS FLUENT 6 6 3 Hooking DEFINE_UDS_UNSTEADY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_UDS_UNSTEADY UDF the name of the argument that you sup plied as the first DEFINE macro argument will become visible and selectable in the User Defined Scalars dialog box in ANSYS FLUENT Make sure that you have selected Transient from the Time list in the Solver group box of the General task page To hook the UDF to ANSYS FLUENT first open the User Defined Scalars dialog box Define User Defined gt Scalars User Defined Scalars Number of User Defined Scalars 2 a v Inlet Diffusion User Defined Scalars
552. pyright 1900 11 09 ANSYS Inc AA y o include include include include if RP_D define else define endif define define define Here THIS 8 76 Copyright 1988 1998 ANSYS Inc All Rights Reserved This is unpublished proprietary source code of ANSYS Inc It is protected by U S copyright law as an unpublished work and is furnished pursuant to a written license agreement It is considered by ANSYS Inc to be confidential and may not be used copied or disclosed to others except in accordance with the terms and conditions of the license agreement Warning Including udf h is for getting definitions for ANSYS FLUENT constructs such as Domain You must NOT reference any ANSYS FLUENT globals directly from within this module nor link this against any ANSYS FLUENT libs doing so will cause dependencies on a specific ANSYS FLUENT binary such as f1551 exe and thus won t be version independent udf h stdio h ctype h stdarg h OUBLE SMLL 1 e 20 SMLL 1 e 10 NSPECIE_NAME 80 RGASU UNIVERSAL_GAS_CONSTANT 8314 34 SI units J Kmol K PI 3 141592654 input the number of species in the mixture IS A USER INPUT Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples define n_specs 5 static int usersMessage char static void usersError char static double ref_p
553. r gt nfstreams Number of fuel streams 2 54 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Pollut_Par gt nfspeli Number of fuel species in stream i NOx gt equiv_ratio i Equivalence ratio for stream i NOx gt c_number i Carbon number for stream i Pollut_Par gt fuel_idx j i Index of jth species in stream i Pollut_Par gt fuel_dup j li Fuel species duplication check Pollut_Par gt uni_R Universal gas constant in SI units Pollut gt temp_m Mean gas temperature K Pollut gt press Pressure in SI units Pollut gt oxy_order Oxygen order please refer to user manual POLLUT_FRATE Pollut POLLUT_RRATE Pollut 0 0 0 0 switch Pollut_Par gt pollut_io_pdf case IN_PDF Included source terms other than those from char if POLLUT_EQN Pollut_Par EQ_NO Prompt NOx if NOx gt prompt_nox amp amp NOx gt prompt_udf_replace int ifstream real f 0 rf Rate_Const K_PM 6 4e6 0 0 36483 49436 for ifstream 0 ifstream lt Pollut_Par gt nfstreams ifstreamt int ij real xc_fuel 0 eqr NOx gt equiv_ratiolifstream for i 0 i lt Pollut_Par gt nfspelifstream i if Pollut_Par gt fuel_dup i ifstream xc_fuel MOLECON Pollut Pollut_Par gt fuel_idx i L ifstream f 4 75 0 0819 NOx gt c_number ifstream 23 2keqr 32 0 pow eqr 2 12 2 pow eqr 3 xc_f
554. r are contained in header files Header files are identified by the h suffix as in mem h metric h and dpm h and are stored in the source code folder path ANSYS Inc v120 fluent fluent12 0 2 src udf h where path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and z is replaced by the appropriate number for the release e g 9 for fluent12 0 9 The header files unless explicitly noted are included in the udf h file so your UDF does not need to contain a special include compiler directive You must however remember to include the include udf h directive in any UDF that you write Access to data from an ANSYS FLUENT solver is accomplished by hooking your UDF C function after it is compiled or interpreted to the code through the graphical user interface GUI After the UDF is correctly hooked the solver s data is passed to the function and is available to use whenever it is called These data are automatically passed by the solver to your UDF as function arguments Note that all solver data regardless of whether they are passed to your UDF by the solver or returned to the solver by the UDF are specified in SI units Macros in this chapter are listed with their arguments argument types returned value s if applicable and header file Each function behind a macro either outputs a value to the solver as an argument or returns a value that is then available for assignment in y
555. r detecting whether the current iteration is the first in the time step PROC o ooo kkk I I I A I kk KAKA A ACA A A kkk kkk kk k kk Example UDF that uses N_TIME BER AAR A AAR I I I A A I KK 1 21 21 2 A 4 24 24 21 21 kkk k kkk kkk kkk static int last_ts 1 Global variable Time step is never lt 0 DEFINE_ADJUST first_iter_only domain int curr_ts curr_ts N_TIME if last_ts curr_ts last_ts curr_ts things to be done only on first iteration of each time step can be put here i There is a new variable named first iteration that can be used in the above if statement first_iteration is true only at the first iteration of a timestep Since the adjust UDF is also called before timestepping begins the two methods vary slightly as to when they are true You must decide which behavior is more appropriate for your case 3 76 Release 12 0 ANSYS Inc January 26 2009 3 6 Scheme Macros 3 6 Scheme Macros The text interface of ANSYS FLUENT executes a Scheme interpreter which allows you to define your own variables that can be stored in ANSYS FLUENT and accessed via a UDF This capability can be very useful for example if you want to alter certain parameters in your case and you do not want to recompile your UDF each time Suppose you want to apply a UDF to multiple zones in a mesh You can do this manually by accessing a particular Zone ID in the graphical user interface hardcoding the integer ID i
556. r limit for the temperature PDF integration see below i Pollut_Par is a pointer to the Pollut Parameter data structure that con tains auxiliary data common to all pollutant species and SOx is a pointer to the SOx_Parameter data structure that contains data specific to the SO model e POLLUT_EQN Pollut Par returns the index of the pollutant equation currently being solved The indices are EQ S02 for SO and EQ_S03 for SOs etc e MOLECON Pollut SPE returns the molar concentration of a species specified by SPE SPE is either the name of the species or IDX i when the species is a pollutant like SO2 For example for O2 molar concentration you should call MOLECON Pollut 02 whereas for SO molar concentration the call should be MOLECON Pollut IDX S02 3 42 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros e ARRH Pollut K returns the Arrhenius rate calculated from the constants specified by K K is defined using the Rate_Const data type and has three elements A B and C The Arrhenius rate is given in the form of R AT exp C T where T is the temperature Note that the units of K must be in m gmol J s e POLLUT_CTMAX Pollut_Par can be used to modify the Tnax value used as the upper limit for the integration of the temperature PDF when temperature is accounted for in the turbulence interaction modeling You must make sure not to put this macro under any conditions within
557. r solids pressure granular radial distribution granular elasticity modulus turbulent viscosity DEF INE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEF INE_PROPERTY DEF INE_TURBULENT_ VISCOSITY secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s secondary phase s mixture primary and secondary phase s Other drag coefficient lift coefficient heat transfer coefficient mass transfer coefficient heterogeneous reaction rate DEFINE EXCHANGE DEF INE_EXCHANGE DEFINE_PROPERTY DEFINE_MASS_TRANS phase interaction phase interaction phase interaction FER phase interaction DEFINE HET RXN_RATE phase interaction C 5 Eulerian Model Dispersed Turbulence Flow Tables C 5 1 C 5 3 list the variables that can be customized using UDFs for the dispersed turbulence flow Eulerian multiphase model the DEFINE macros that are used to define the UDFs and the phase that the UDF needs to be hooked to for the given variable C 10 Release 12 0 ANSYS Inc January 26 2009 C 5 Eulerian Model Dispersed Turbulence Flow Table C 5 1 DEFINE Macro Usage for the Eulerian Model Dispersed Tur bulence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magn
558. rations Recall that from Section 7 2 Cells and Faces in a Partitioned Mesh a face may appear in one or two partitions but in order that summation operations don t count it twice it is officially allocated to only one of the partitions The tests above are used with the neighboring cell s partition ID to determine if it belongs to the current partition The convention that is used is that the smaller numbered compute node is assigned as the principal compute node for that face PRINCIPAL_FACE_P returns TRUE if the face is located on its principal compute node The macro can be used as a test condition when you want to perform a global sum on faces and some of the faces are partition boundary faces The macro returns TRUE for the serial process Below is the definition of PRINCIPAL FACE P from para h See Section 7 2 Cells and Faces in a Partitioned Mesh for more information about PRINCIPAL_FACE_P predicate definitions from para h header file define PRINCIPAL_FACE_P f t TWO_CELL_FACE_P f t PRINCIPAL_TWO_CELL_FACE_P f t define PRINCIPAL_TWO_CELL_FACE_P f t I_LAM_NODE_MORE_P C_PART F_CO f t THREAD_TO t T_AM_NODE_MORE_P C_PART F_C1 f t THREAD_T1 t 7 5 4 Global Reduction Macros Global reduction operations are those that collect data from all of the compute nodes and reduce the data to a single value or an array of values These include operations such as global summations global max
559. read begin_c_loop c c_thread loops over cells in a cell thread end_c_loop c c_thread Example Loop over cells in a thread to get information stored in cells begin_c_loop c c_thread C_T gets cell temperature The will cause all of the cell temperatures to be added together temp C_T c c_thread end_c_loop c c_thread Looping Over Faces in a Face Thread begin end_f_loop You can use begin_f_loop and end_f_loop when you want to loop over all faces in a given face thread It contains a begin and end loop statement and performs operation s on each face in the face thread as defined between the braces This loop is usually nested within thread_loop_f when you want to loop over all faces in all face threads in a domain face_t f Thread f_thread begin_f_loop f f_thread loops over faces in a face thread end_f_loop f f_thread Release 12 0 ANSYS Inc January 26 2009 3 57 Additional Macros for Writing UDFs Example Loop over faces in a face thread to get the information stored on faces begin_f_loop f f_thread F_T gets face temperature The will cause all of the face temperatures to be added together temp F_T f f_thread end_f_loop f f_thread Looping Over Faces of a Cell c_face_loop The following looping function loops over all faces of a given cell It consists of a single loop statement followed by the actio
560. read since ANSYS FLUENT is doing it outside of the function call 2 34 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example The following UDF named mean_age_diff computes the diffusivity for the mean age of air using a user defined scalar Note that the mean age of air calculations do not require that energy radiation or species transport calculations have been performed You will need to set uds 0 0 0 at all inlets and outlets in your model This function can be executed as an interpreted or compiled UDF PROC kkk kk kkk kk kk kk kk kk k kkk k kk k k I k I I k k k k k k kk k A A Kk k k kk k k 4 4 2k UDF that computes diffusivity for mean age using a user defined scalar FRR RA a A ak a 3k 2k ak 2k 2k a 3k 2k 2k a 2k 2k 2 ak 2k 2k a ak include udf h DEFINE_DIFFUSIVITY mean_age_diff c t i return C_R c t 2 88e 05 C_MU_EFF c t 0 7 Hooking a Diffusivity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DIFFUSIVITY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified in the DEFINE macro argument e g mean_age_diff will become visi ble and selectable in the Create Edit Materials dialog box in ANSYS FLUENT See Sec tion 6 2 3 Hooking DEFINE DIFFUSIVITY UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 35 DEFINE Macros 2 3 4 DEFINE_DOM_DIFFUSE_REFLECTIVITY Descripti
561. receding it udf unsteady_pressure from the Gauge Pressure drop down list Click OK to accept the new boundary condition and close the dialog box The user defined profile will be used in the subsequent solution calculation EME eee comellia cimos gt Edit Pressure Outlet Zone Name pressure outlet 5 Momentum Thermal Radiation Species DPM Multiphase UDS Gauge Pressure pascal udf unsteady_pressure Backflow Direction Specification Method Normal to Boundary C Target Mass Flow Rate Figure 8 2 7 The Pressure Outlet Dialog Box The time stepping parameters are set in the Run Calculation task page Figure 8 2 8 8 20 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Ma Run Calculation Run Calculation Check Case Pre Time Stepping Method Time Step Size s Fixed 0 0314 Number of Time Steps 300 a v Options C Extrapolate variables C Data Sampling for Time Statistics Max Iterations Time Ste Reporting Interval 20 a 20 a v v Profile Update Interval 1 7 Data File Quantities Calculate Figure 8 2 8 The Run Calculation Task Page In this example a Time Step Size of 0 0314 s is used so that 20 time steps will complete a full period of oscillation in the outlet velocity The Profile Update Interval is set to 1 so that the pre
562. ree arguments to DEFINE_TRANS_RETHETA_T name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the transition onset momentum thickness Reynolds number to the solver Example The following functions which are concatenated into a single C source code file demon strate this usage 2 1 20 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros include udf h DEFINE_TRANS_FLENGTH user_Flength c t real Flength 31 468 return Flength J DEFINE_TRANS_RETHETA_C user_Re_thetac c t real Re_thetac 176 396 return Re_thetac J DEFINE_TRANS_RETHETA_T user_Re_thetat c t real Re_thetat 210 return Re_thetat Hooking a Transition Correlation UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_TRANS is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the DEFINE macro argument e g user_Re_thetat will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Sec tion 6 2 23 Hooking DEFINE_TRANS UDFs for details Release 12 0 ANSYS Inc January 26 2009 2 1 21 DEFINE Macros 2 3 24 DEFINE_TURB_PREMIX_SOURCE Description You can use DEFINE_TURB_PREMIX_SOURCE to customize the turbulent flame speed and source term
563. ref_T static char gas n_specs NSPECIE_NAME static property parameters static double cp 5 n_specs specific heat polynomial coefficients static double mw n_specs molecular weights static double hf n_specs formation enthalpy static double tcrit n_specs critical temperature static double pcrit n_specs critical pressure static double vcrit n_specs critical specific volume static double nrk n_specs exponent n of function a T in Redlich Kwong equation of state static double omega n_specs acentric factor Static variables associated with Redlich Kwong Model static double rgas n_specs aO n_specs bO n_specs cO n_specs bb n_specs cp_int_ref n_specs void Mw void Cp_Parameters void Hform void Tcrit void Pcrit void Vcrit void NRK void Omega double RKEOS_spvol double temp double press int i double RKEOS_dvdp double temp double density int i double RKEOS_dvdt double temp double density int i double RKEOS_H_ideal_gas double temp int i double RKEOS_specific_heat double temp double density int i double RKEOS_enthalpy double temp double density int i double RKEOS_entropy double temp double density int i double RKEOS_viscosity double temp int i double RKEOS_thermal_conductivity double temp int i double RKEOS_vol_specific_heat double temp double density int i Release 12 0
564. responding elements on the compute nodes are TRUE By contrast PRF_GLAND x computes the global logical AND across all compute nodes and PRF_GLAND x N iwork computes the global logical AND of variable array x The elements of x are set to TRUE if all of the corresponding elements on the compute nodes are TRUE Release 12 0 ANSYS Inc January 26 2009 7 21 Parallel Considerations Global Logicals Macro Action PRF_GLOR1 x TRUE when variable x is TRUE for any of the compute nodes PRF_GLOR x N work TRUE when any of the elements in variable array x is TRUE PRF_GLAND1 x TRUE when variable x is TRUE for all compute nodes PRF_GLAND x N iwork TRUE when every element in variable array x is TRUE Global Synchronization PRF_GSYNC can be used when you want to globally synchronize compute nodes before proceeding with the next operation When you insert a PRF_GSYNC macro in your UDF no commands beyond it will execute until the preceding commands in the source code have been completed on all of the compute nodes Synchronization may also be useful when debugging your function 7 5 5 Looping Macros There are three types of cell looping macros that are available for parallel coding one that loops over interior cells only exterior cells only and both interior and exterior cells Looping Over Cells A partitioned mesh in parallel ANSYS FLUENT is made up of interior cells and exterior cells see Figure 7 2 1 There is a set of c
565. rgument will become visible and selectable in ANSYS FLUENT There are various dialog boxes in which you can activate a DEFINE_PROPERTY UDF e g Phase Interaction dialog box Secondary Phase dialog box and so the method for hooking it will depend on the property being defined The following is an example of hooking a UDF that defines viscosity First open the Materials task page lt BWEarlS Select the appropriate material from the Material selection list and click the Create Edit button to open the Create Edit Materials dialog box Figure 6 2 20 6 36 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs Create Edit Materials Name liguid_metal Material Type fluid Order Materials by v Name Chemical Formula O Chemical Formula FLUENT Fluid Materials E FLUENT Database liquid_metal Properties Density kg m3 arctan 8000 Cp Specific Heat j kg k r 680 constant Thermal Conductivity w m k 30 Viscosity kg m s user defined v cell_viscosity User Defined Database v Figure 6 2 20 The Create Edit Materials Dialog Box Next open the User Defined Functions dialog box Figure 6 2 21 by choosing user defined in the drop down list for the appropriate property e g Viscosity in the Create Edit Materials dialog box Then select the function name e
566. rgy RP_Get_Real spark duration vol return source else return 0 else return 0 endif i Interpreted UDFs cannot be used while running in parallel with an Infini band interconnect The compiled UDF approach should be used in this case 7 7 Process Identification Each process in parallel ANSYS FLUENT has a unique integer identifier that is stored as the global variable myid When you use myid in your parallel UDF it will return the integer ID of the current compute node including the host The host process has an ID of node host 999999 and is stored as the global variable node_host Compute node 0 has an ID of 0 and is assigned to the global variable node_zero Below is a list of global variables in parallel ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 7 35 Parallel Considerations Global Variables in Parallel ANSYS FLUENT int node_zero 0 int node_host 9 int node_one 1 int node_serial 1000000 99999 int node_last returns the id of the last compute node int compute_node_count returns the number of compute nodes int myid returns the id of the current compute node and host myid is commonly used in conditional if statements in parallel UDF code Below is some sample code that uses the global variable myid In this example the total number of faces in a face thread is first computed by accumulation Then if myid is not compute node
567. rho_t drho dT const p RKEOS_rho_p drho dp const T RKEOS_enthalpy_t dh dT const p RKEOS_enthalpy_p dh dp const T UDRGM Example Multiple Species Real Gas Model This is a simple example for multiple species real gas model that provide you with a template which you can use to write a more complex multiple species UDRGM In this example a fluid material is defined in the setup function as a mixture of four species H20 N2 O2 CO2 The equation of state was the simple ideal gas equation of state The other thermodynamic properties where defined by an ideal gas mixing law Other auxiliary functions are written to provide individual species property to the prin ciple function set dp dp dh dh The example also provide numerical method of computing F dp dT and dp sccs id real_ideal c 1 10 Copyright 1900 11 09 ANSYS Inc Copyright 1988 1998 ANSYS Inc All Rights Reserved Release 12 0 ANSYS Inc January 26 2009 8 65 Examples This is unpublished proprietary source code of ANSYS Inc It is protected by U S copyright law as an unpublished work and is furnished pursuant to a written license agreement It is considered by ANSYS Inc to be confidential and may not be used copied or disclosed to others except in accordance with the terms and conditions of the license agreement Windows Warning Including udf h is for getting
568. riables are introduced temp the value of C_T cell thread and mu_lam the laminar viscosity computed by the function The value of the temperature is checked and based upon the range into which it falls the appropriate value of mu_lam is computed At the end of the function the computed value for mu_lam is returned to the solver K k k k k 2k 2k CCA RA AK K 2K 2K FK 2K 2K 2K 2K 2K 2K K K 2K FK 2K 2K 2K 2K AK AK 2K K 2k 2K 2K 2k FK 2K 2k 2k 2K 2k 2k K 2k 2k FK FK UDF for specifying a temperature dependent viscosity property BER ooo A A IK KK KK o kkk kk kkk kk kkk include udf h DEFINE_PROPERTY cell_viscosity cell thread real mu_lam real temp C_T cell thread if temp gt 288 mu_lam 5 5e 3 else if temp gt 286 mu_lam 143 2135 0 49725 temp else mu_lam 1 return mu_lam Release 12 0 ANSYS Inc January 26 2009 8 31 Examples This function can be executed as an interpreted or compiled UDF in ANSYS FLUENT Follow the procedure for interpreting source files using the Interpreted UDFs dialog box Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box or compiling source files using the Compiled UDFs dialog box Section 5 2 Compiling a UDF Using the GUI To make use of the user defined property in ANSYS FLUENT you will need to open the Create Edit Materials dialog box Figure 8 2 18 by selecting the liquid metal material in the Materials task page and c
569. rn intensity Hooking a Solar Intensity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_SOLAR_INTENSITY is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name that you specified e g sol_direct_intensity in the DEFINE macro argument will be come visible and selectable for Direct Solar Irradiation and Diffuse Solar Irradiation in the Radiation Model dialog box in ANSYS FLUENT Note that the solar load model must be enabled See Section 6 2 18 Hooking DEFINE_SOLAR_INTENSITY UDF for details Release 12 0 ANSYS Inc January 26 2009 2 99 DEFINE Macros 2 3 19 DEFINE_SOURCE Description You can use DEFINE SOURCE to specify custom source terms for the different types of solved transport equations in ANSYS FLUENT except the discrete ordinates radiation model including e mass e momentum e k e energy also for solid zones e species mass fractions e PI radiation model e user defined scalar UDS transport e granular temperature Eulerian Mixture multiphase models Usage DEFINE _SOURCE name c t dS eqn Argument Type Description symbol name UDF name cellt c Index that identifies cell on which the source term is to be applied Thread t Pointer to cell thread real dS Array that contains the derivative of the source term with respect to the dependent variable of the transport equation int eqn Equation number Function returns real 2 1
570. roperties and variables are needed a sum over phases the superdomain is used for those quantities while the subdomain carries the information for individual phases In single phase the concept of a mixture is used to represent the sum over all the species components while in multiphase it represents the sum over all the phases This distinction is important because ANSYS FLUENT has the capability of handling multiphase multi components where for example a phase can consist of a mixture of species Since solver information is stored in thread data structures threads must be associated with the superdomain as well as with each of the subdomains In other words for each cell or face thread defined in the superdomain there is a corresponding cell or face thread defined for each subdomain Some of the information defined in one thread of the superdomain is shared with the corresponding threads of each of the subdomains Threads associated with the superdomain are referred to as superthreads while threads associated with the subdomain are referred to as phase level threads or subthreads The domain and thread hierarchy are summarized in Figure 1 10 1 Release 12 0 ANSYS Inc January 26 2009 1 17 Overview Mixture level thread e g inlet zone Mixture level thread e g fluid zone Mixture domain domain_id 1 Interaction domains domain_id 5 6 7 Primary phase domain domain_id
571. ros e Section 2 5 Discrete Phase Model DPM DEFINE Macros e Section 2 6 Dynamic Mesh DEFINE Macros e Section 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros 2 1 Introduction DEFINE macros are predefined macros provided by ANSYS Inc that must be used to define your UDF A listing and discussion of each DEFINE macros is presented below Refer to Section 1 4 Defining Your UDF Using DEFINE Macros for general information about DEFINE macros Definitions for DEFINE macros are contained within the udf h file For your convenience they are provided in Appendix B For each of the DEFINE macros listed in this chapter a source code example of a UDF that utilizes it is provided where available Many of the examples make extensive use of other macros presented in Chapter 3 Additional Macros for Writing UDFs Note that not all of the examples in the chapter are complete functions that can be executed as stand alone UDFs in ANSYS FLUENT Examples are intended to demonstrate DEFINE macro usage only Special care must be taken for some serial UDFs that will be run in parallel ANSYS FLUENT See Chapter 7 Parallel Considerations for details Note that all of the arguments to a DEFINE macro need to be placed on the same line in your source code Splitting the DEFINE statement onto several lines will result in a compilation error Release 12 0 ANSYS Inc January 26 2009 2 1 DEFINE Macros i Make sure that there are no
572. ros They can send messages indirectly to the host through compute node 0 For example if you want your parallel UDF to send data from all of the compute nodes to the host for postprocessing purposes the data will first have to be passed from each compute node to compute node 0 and then from compute node 0 to the host In the case where the compute node processes send a message to compute node 0 compute node 0 must have a loop to receive the N messages from the N nodes Below is an example of a compiled parallel UDF that utilizes message passing macros PRF_CSEND and PRF_CRECV Refer to the comments in the code for details about the function Example Message Passing include udf h define WALLID 3 DEFINE_ON_DEMAND face_p_list if RP_HOST Host will do nothing in this udf Serial will face_t f Thread tf Domain domain real p_array real x ND_ND x_array ND_ND int n_faces i j domain Get_Domain 1 Each Node will be able to access its part of the domain tf Lookup_Thread domain WALLID Get the thread from the domain The number of faces of the thread on nodes 1 2 needs to be sent to compute node O so it knows the size of the arrays to receive from each n_faces THREAD_N_ELEMENTS_INT tf 7 30 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs No need to check for Principal Faces as this UDF will be used for boundary zones only if RP_N
573. rrrrrretrrrrrrretrrrrrrrrree et ts 9 include udf h define CON 20 0 DEFINE_SOURCE cell_x_source cell thread dS eqn real source if C_T cell thread lt 288 source CON C_U cell thread dS eqn CON else source dS eqn 0 return source To make use of this UDF in ANSYS FLUENT you will first need to interpret or compile the function and then hook it to ANSYS FLUENT using the graphical user interface Follow the procedure for interpreting source files using the Interpreted UDFs dialog box Section 4 2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box 8 26 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples or compiling source files using the Compiled UDFs dialog box Section 5 2 Compiling a UDF Using the GUID To include source terms in the calculation you will first need to open the Fluid dialog box Figure 8 2 13 by selecting the fluid zone in the Cell Zone Conditions task page and clicking Edit Aeon ne Edit Zone Name fluid 8 1 Material Name iquid_metal C Porous Zone Source Terms C Fixed values Motion eea Reaction Source Terms Fixed Values Mass ka m3 s 9 sources X Momentum njm3 fy source Y Momentum n m3 0 sources Energy wim3 0 sources Figure 8 2 13 The Fluid Dialog Box Enable the Source Terms option in the Fluid dialog box and cli
574. rs for an example 3 2 6 Special Macros The macros listed in this section are special macros that are used often in UDFs e Lookup_Thread THREAD_ID Get_Domain F_PROFILE THREAD_SHADOW Thread Pointer for Zone ID Lookup_Thread You can use Lookup_Thread when you want to retrieve the pointer t to the thread that is associated with a given integer zone ID number for a boundary zone The zone_ID that is passed to the macro is the zone number that ANSYS FLUENT assigns to the boundary and displays in the boundary condition dialog box e g Fluid Note that this macro does the inverse of THREAD_ID see below There are two arguments to Lookup_Thread domain is passed by ANSYS FLUENT and is the pointer to the domain structure You supply the integer value of zone_ID For example the code int zone_ID 2 Thread thread_name Lookup_Thread domain zone_ID passes a zone ID of 2 to Lookup_Thread A zone ID of 2 may for example correspond to a wall zone in your case Now suppose that your UDF needs to operate on a particular thread in a domain instead of looping over all threads and the DEFINE macro you are using to define your UDF doesn t have the thread pointer passed to it from the solver e g DEFINE_ADJUST You can use Lookup_Thread in your UDF to get the desired thread pointer This is a two step process Release 12 0 ANSYS Inc January 26 2009 3 29 Additional Macros for Writing UDFs First you will
575. ry 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros 2 5 6 DEFINE_DPM_INJECTION_INIT Description You can use DEFINE _DPM_INJECTION_INIT to initialize a particle s injection properties such as location diameter and velocity Usage DEFINE_DPM_INJECTION_INIT name T Argument Type Description symbol name UDF name Injection I Pointer to the Injection structure which is a container for the particles being created This function is called twice for each Injection before the first DPM iteration and then called once for each Injection before the particles are injected into the domain at each subsequent DPM iteration Function returns void There are two arguments to DEFINE_DPM_INJECTION_INIT name and I You supply name the name of the UDF I is a variable that is passed by the ANSYS FLUENT solver to your UDF Example The following UDF named init_bubbles initializes particles on a surface injection due to a surface reaction This function must be executed as a compiled UDF and can be used only on UNIX and Linux systems Note that if you are going to use this UDF in a transient simulation to compute transient particles you will need to replace loop p I gt p with loop p I gt p_init Transient particle initialization cannot be performed with a loop over I gt p Release 12 0 ANSYS Inc January 26 2009 2 1 77 DEFINE Macros peaa o kkk kkk kkk kkk k kk kkk kkk kk kkk kkk kk A kk kk kkk k k 4 k UDF tha
576. ry phase defined for your multiphase model you will need to use the PHASE_DOMAIN_INDEX utility to retrieve the corresponding phase_domain_index for the given domain See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details 3 66 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros Phase Thread Pointer Array THREAD_SUB_THREAD The THREAD_SUB_THREADS macro can be used to retrieve the pointer array pt whose elements contain pointers to phase level threads subthreads THREADS_SUB_THREADS has one argument mixture_thread Thread mixture_thread Thread pt initialize pt pt THREAD_SUB_THREADS mixture_thread mixture_thread is a pointer to a mixture level thread which can represent a cell thread or a face thread It is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a variable thread argument e g DEFINE PROFILE and the function is hooked to the mixture Otherwise if the mixture thread pointer is not explicitly passed to your UDF then you will need to use another method to retrieve it For example you can use the Lookup_Thread utility macro see Section 3 2 6 Thread Pointer for Zone ID Lookup Thread pti an element in the array is a pointer to the corresponding phase level thread for the ith phase where i is the phase_domain_index You can use pt i as an argument to some cell variable macros when you want to retrieve specific phas
577. s 6 1 4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs 6 1 5 Hooking DEFINE INIT UDPS s sess 426404 ha o4 4 4 6 1 6 Hooking DEFINE ON DEMAND UDFs 48 6 5s5 4 45 40684 6 1 7 Hooking DEFINE RW FILE UDES gp c t miet og t 8 lt 0ive s 6 1 8 User Defined Memory Storage aoaaa e 6 2 Hooking Model Specific UDFs a a aaa aa 6 21 Hooking DEFINE CHEM STEP UDFs 4 oc hk eo eke ok ws 6 2 2 Hooking DEFINE CPHI UDFs o 2 4 525 ba be ee eee 6 2 5 Hooking DEFINE DIFFUSIVITY UDPS s ssi at rateta 6 2 4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs 6 2 5 Hooking DEFINE DOM SOURCE UDFs ca 2 406 komi wor poena 6 2 6 Hooking DEFINE DOM_SPECULAR REFLECTIVITY UDFs 6 2 7 Hooking DEFINE EMISSIVITY WEIGHTING FACTOR UDFs 6 2 8 Hooking DEFINE_GRAY_BAND_ABS_COEFF UDFs Release 12 0 ANSYS Inc January 26 2009 CONTENTS 6 29 Hooking DEFINE FEAT FLX UDPS s essa ee mist ana ee eS 6 24 6 2 10 Hooking DEFINE_IGNITE_SOURCE UDFs 6 25 6 2 11 Hooking DEFINE NET REACTION RATE UDFs 6 26 6 2 12 Hooking DEFINE NOX RATE UDES gt a o sei sa eh Yat areas 6 28 6 2 13 Hooking DEFINE PRRATE UDFs aaanaa ee be we aaa 6 29 6 2 14 Hooking DEFINE PRANDTL UDFs 2 2 444 44454 44 4 6 31 6 2 15 Hooking DEFINE PROFILE UDFS lt vs4 4 4248 4 6 32 6 2 16 Hooking DEFINE PROPERTY UDPSe oc d 4 eeu roepa k p ewh 6 36 6 2 17 Hooking DEFINE_SCAT_PHASE_FUNC UDFs 6 38 6 2 18 Hoo
578. s These are the only functions called from ANSYS FLUENT Code DOR aaao ooa ooo oo kkk k kkk kk k kkk void MIXTURE_Setup Domain domain cxboolean vapor_phase char specielist int messagefunc char format void errorfunc char format This function will be called from ANSYS FLUENT after the UDF library has been loaded User must enter the number of species in the mixture and the name of the individual species int i usersMessage messagefunc usersError errorfunc ref_p ABS_P RP_Get_Real reference pressure op_pres Release 12 0 ANSYS Inc January 26 2009 8 67 Examples ref_T RP_Get_Real reference temperature if ref_p 0 0 MessageO n MIXTURE_Setup reference pressure was not set by user n MessageO n MIXTURE_Setup setting reference pressure to 101325 Pa n ref_p 101325 0 e e a e a a e a T User Input Section XSSSSSSSSSSS esas SSS aS SSS SSS SS esas e SSeS sSSSSesasa Define Number of species amp Species name DO NOT use space for naming species n_specs 4 void strcpy gas 0 H20 void strcpy gas 1 N2 void strcpy gas 2 02 void strcpy gas 3 C02 End Of User Input Section S Message0 n MIXTURE_Setup RealGas mixture initialization n MessageO n MIXTURE_Setup Number of Species d n n_specs for i 0 i lt
579. s 6 79 Release 12 0 ANSYS Inc January 26 2009 Hooking UDFs to ANSYS FLUENT 6 4 15 Hooking DEFINE_DPM_VP_EQUILIB UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_VP_EQUILIB UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable from the Create Edit Materials dialog box in ANSYS FLUENT To hook the UDF first set up your species transport and combustion models in the Species Model dialog box A Seets Edit Then create a particle injection using the Injections dialog box Define gt lnjections Click Create in the Injections dialog box to open the Set Injection Properties dialog box Set up the particle injection making sure to select Multicomponent for the Particle Type Next open the Materials task page lt aterials Select the appropriate material in the Materials list e g particle mixture template and click Create Edit to open the Create Edit Materials dialog box Figure 6 4 16 Create Edit Materials Name 7 Material Type Order Materials by particle mixture template particle mixture g Name 1 chemical Formula tile BELL FLUENT Particle Mixture Materials particle mixture template v FLUENT Database f User Defined Database Properties Density kg m3 ondak 1 Cp Spe
580. s it is best to consider how the aforementioned calculations are evaluated Assuming that the gradient of a scalar is available the face value of a scalar can be approximated by os po Vo dr 3 2 1 where dr is the vector that connects the cell centroid with the face centroid The gradient in this case is evaluated at the cell centroid where o is also stored The diffusive flux Dp across a face f of a scalar is given by D T Vo A 3 2 2 where I is the diffusion coefficient at the face In ANSYS FLUENT s unstructured solver the gradient along the face normal direction may be approximated by evaluating gradients along the directions that connect cell centroids and along a direction confined within the plane of the face Given this Ds may be approximated as iG AA gt A D T I Vo A Vo amp 3 2 3 f d Ig 4 9 Ae where the first term on the right hand side represents the primary gradient directed along the vector and the second term represents the cross diffusion term In this equation A is the area normal vector of face f directed from cell cO to c1 ds is the distance between the cell centroids and amp is the unit normal vector in this direction V is the average of the gradients at the two adjacent cells For boundary faces the variable is the gradient of the c0 cell This is shown in Figure 3 2 2 Release 12 0 ANSYS Inc January 26 2009 3 25 Additiona
581. s spe lam Figure 8 2 23 The Outline of the 2D Duct Through the inlet on the left gas that is purely species a enters with an x velocity of 0 1 m s The gas enters both the open region on the top of the porous medium and the porous medium itself where there is an inertial resistance of 5 m in each of the two coordinate directions The laminar flow field Figure 8 2 24 shows that most of the gas is diverted from the porous region into the open region The flow pattern is further substantiated by the vector plot shown in Figure 8 2 25 The flow in the porous region is considerably slower than that in the open region 8 36 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples wi ANSYS 1 46e 0 1 30e 0 1 14e 0 9 73e 01 8 11e 0 6 49e 01 4 87e 0 3 24e 01 1 62e 01 0 00e 00 Contours of Stream Function kg s FLUENT 12 0 2d pbns spe lam Figure 8 2 24 Streamlines for the 2D Duct with a Porous Region 2 32e0 ANSYS 2 09e 01 1 86e 01 1 63e 01 1 39e 01 SSS SSS SSS 1 16 01 9 31e 02 6 99e 02 4 68e 02 2 36e 02 4 40e 04 Velocity Vectors Colored By Velocity Magnitude m s FLUENT 12 0 2d pbns spe lam Figure 8 2 25 Velocity Vectors for the 2D Duct with a Porous Region Release 12 0 ANSYS Inc January 26 2009 8 37 Examples The source code rate c that
582. s about DEFINE_DOM_SOURCE functions 6 20 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 6 Hooking DEFINE_DOM_SPECULAR_REFLECTIVITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_SPECULAR_REFLECTIVITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 8 in ANSYS FLUENT The discrete ordinates DO radiation model must be enabled from the Radiation Model dialog box To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 8 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Chemistry Step Cavitation Mass Rate DO Source DO Diffuse Reflectivity DO Specular Reflectivity Pmp ibudF DO Emissivity Weighting Factor Figure 6 2 8 The User Defined Function Hooks Dialog Box Select the function name e g user_dom_spec_refl libudf in the DO Specular Reflectivity drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 4 DEFINE_DOM_DIFFUSE_REFLECTIVITY for details about DEFINE_DOM_SPECULAR_REFLECTIVITY functions Release 12 0 ANSYS Inc January 26 2009 6
583. s at a fixed reference pressure p the entropy is given by COT T S T p S T p L 8 2 28 Note that the pressure term is zero since the entropy is evaluated at the reference pres sure Using the polynomial expression for specific heat Equation 8 2 21 Equation 8 2 28 becomes S T p S T p C1 n T CT Ox O TOT f T 8 2 29 where f T is a constant which can be absorbed into the reference entropy S T p Speed of Sound The speed of sound for a real gas can be determined from the thermodynamic relation Op C y r 2 8 2 30 Ob s A Se Noting that OV Vo G sT p 5 8 2 31 p T we can write the speed of sound as Cp 1 c V 5 e3 8 2 32 Op T Viscosity and Thermal Conductivity The dynamic viscosity of a gas or vapor can be estimated using the following formula from 2 u T 6 3 x 10 M25 0 6666 T15 w Pe r 8 2 33 701666 T 0 8 8 52 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples Here T is the reduced temperature T a 8 2 34 and Maw is the molecular weight of the gas This formula neglects the effect of pressure on viscosity which usually becomes significant only at very high pressures Knowing the viscosity the thermal conductivity can be estimated using the Eucken formula 4 a c R 8 2 35 It should be noted that both Equation 8 2 33 and 8 2 35 are simple relatio
584. s depends on 1 the selected Solver density based or pressure based 2 the selected Model 3 the order of discretizations 4 whether the temporary solver memory is being retained to keep temporary memory go to solve gt set gt expert and type YES for Keep temporary solver memory from being freed How to use showgrad Read in your case amp data file Compile showgrad c UDF Load library libudf Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Attach the showgrad UDF in the Execute on Demand dialog box Run your solution Click the Execute button in the Execute on Demand dialog box A list of available Grads and Recon Grads will be displayed in the console EFEFEF o o 2004 Laith Zori include udf h DEFINE_ON_DEMAND showgrad Domain domain Thread t domain Get_Domain 1 if Data_Valid_P return Message0 gt gt gt entering show grad n thread_loop_c t domain Material m int nspe int nspm THREAD_MATERIAL t MIXTURE_NSPECIES m nspe 1 Message0 n Message0 Reconstruction Gradients Peis Ani D MessageO n if NNULLP THREAD_STORAGE t SV_P_RG Message0 show grad Reconstruction Gradient of P is available n if NNULLP THREAD_STORAGE t SV_U_RG ge Message0 show grad Reconstruction Gradient of U is available n if NNULLP THREAD_STORAGE t SV_V_RG Release 12 0
585. s in Chapter 2 DEFINE Macros In addition a step by step example mini tutorial and detailed examples can be found in Chapter 8 Examples 1 3 Limitations Although the UDF capability in ANSYS FLUENT can address a wide range of applica tions it is not possible to address every application using UDFs Not all solution variables or ANSYS FLUENT models can be accessed by UDFs If you are unsure whether a par ticular problem can be handled using a UDF contact your technical support engineer for assistance i Note that you may need to update your UDF when using a new version of ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 1 3 Overview 1 4 Defining Your UDF Using DEFINE Macros UDFs are defined using ANSYS FLUENT supplied function declarations These function declarations are implemented in the code as macros and are referred to in this document as DEFINE all capitals macros Definitions for DEFINE macros are contained in the udf h header file see Appendix B for a listing For a complete description of each DEFINE macro and an example of its usage refer to Chapter 2 DEFINE Macros The general format of a DEFINE macro is DEFINE_MACRONAME udf_name passed in variables where the first argument in the parentheses is the name of the UDF that you supply Name arguments are case sensitive and must be specified in lowercase The name that you choose for your UDF will become visible and selectable in drop down lists in
586. s not included in udf h You will need to include this file in your UDF using the include directive i The use of BOUNDARY SECONDARY GRADIENT SOURCE first requires that cell geometry information be defined which can be readily obtained by the use of the BOUNDARY_FACE_GEOMETRY macro described previously in this section See Section 8 2 5 Implementing ANSYS FLUENT s P 1 Radiation Model Using User Defined Scalars for an example BOUNDARY_SECONDARY_GRADIENT_SOURCE can be called to retrieve some of the terms needed to evaluate Equation 3 2 3 real source the cross diffusion term of the diffusive flux i e the second term on the right side of Equation 3 2 3 real n the average of the facial gradient V in Equation 3 2 3 real dphi ND_ND a dummy scratch variable array that stores the facial gradient value during the computation real dx ND_ND the unit normal vector in the direction from centroid of cell c0 to the face centroid real A byes the value oo real k the diffusion coefficient at the face T p in Equation 3 2 3 3 28 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros i Note that the average of the facial gradient supplied for n is not always allocated and so your UDF must verify its status using the NULLP or NNULLP function as described in Section 3 8 NULLP amp NNULLP and assign a value as necessary See Section 8 2 5 Implementing ANSYS FLUENT s P 1 Radiation Model Using User Defined Scala
587. s number is to be applied Thread t Pointer to cell thread Function returns real There are three arguments to DEFINE_TRANS_RETHETA_C name c and t You supply name the name of the UDF c and t are variables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to return the real value for the critical momentum thickness Reynolds number to the solver Example An example of a TRANS RETHETA C UDF is provided at the end of this section Release 12 0 ANSYS Inc January 26 2009 2 1 19 DEFINE Macros Hooking a Transition Correlation UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_TRANS_RETHETA_C is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the DEFINE macro argument e g user_Re_thetac will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 23 Hooking DEFINE_TRANS UDFs for details DEF INE_TRANS_RETHETA_T Description You can use DEFINE_TRANS_RETHETA_T to specify the transition onset momentum thick ness Reynolds number for the Transition SST turbulence model Usage DEFINE_TRANS_RETHETA_T name c t Argument Type Description symbol name UDF name cell_t c Index that identifies the cell on which the transition onset momentum thickness Reynolds number is to be applied Thread t Pointer to cell thread Function returns real There are th
588. s used by the sampler then plane is NULL Function returns void There are six arguments to DEFINE_DPM_OUTPUT name header fp p t and plane You supply name the name of the UDF header fp p t and plane are variables that are passed by the ANSYS FLUENT solver to your UDF The output of your UDF will be written to the file indicated by fp Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Release 12 0 ANSYS Inc January 26 2009 2 1 83 DEFINE Macros Example The following UDF named discrete_phase_sample samples the size and velocity of dis crete phase particles at selected planes downstream of an injection For 2d axisymmetric simulations it is assumed that droplets particles are being sampled at planes lines cor responding to constant x For 3d simulations the sampling planes correspond to constant z To remove particles from the domain after they have been sampled change the value of REMOVE_PARTICLES to TRUE In this case particles will be deleted following the time step in which they cross the plane This is useful when you want to sample a spray immediately in front of an injector and you don t wish to track the particles further downstream This UDF works with unsteady and steady simulations that include droplet break up or collisions Note that the discrete phase must be traced in an unst
589. s_mix sp ns molwt ns MATERIAL_PROP sp PROP_mwi molecular weight of gas species molwt_bulk c gt yi ns molwt ns average molecular weight prevent division by zero molwt_bulk MAX molwt_bulk DPM_SMALL 2 1 74 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros for ns 0 ns lt nc nst 4 int gas_index TP_COMPONENT_INDEX_I p ns gas species index of vaporization if gas_index gt 0 condensed material Material cond_c MIXTURE_COMPONENT cond_mix ns vaporization temperature real vap_temp MATERIAL_PROP cond_c PROP_vap_temp diffusion coefficient real D MATERIAL_PROP_POLYNOMIAL cond_c PROP_binary_diffusivity c gt temp Schmidt number real Sc c gt mu c gt rho D mass transfer coefficient real k 2 0 6 sqrt p gt Re pow Sc 1 3 D Dp bulk gas concentration ideal gas real cvap_bulk c gt pressure UNIVERSAL_GAS_CONSTANT c gt temp x c gt yilgas_index molwt_bulk solver_par molWeight gas_index vaporization rate real vap_rate k molwt gas_index Ap x cvap_surf ns cvap_bulk no vaporization below vaporization temperature no condensation if Tp lt vap_temp vap_rate lt 0 0 vap_rate 0 dydt 1t ns vap_rate dzdt gt species gas_index vap_rate aT dt dh dt m Cp dydt 0 hvap gas_i
590. scattering coefficient Function returns void There are nine arguments to DEFINE_DOM_SOURCE name c ni nb emission in scattering abs_coeff and scat_coeff You supply name the name of the UDF c ni nb emission in scattering abs_coeff and scat_coeff are variables that are passed by the ANSYS FLUENT solver to your UDF DEFINE_DOM_SOURCE is called by ANSYS FLUENT for each cell 2 38 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example In the following UDF named dom the emission term present in the radiative transport equation is modified The UDF is called for all the cells and increases the emission term by 5 UDF to alter the emission source term in the DO model include udf h DEFINE_DOM_SOURCE dom c t ni nb emission in_scattering abs_coeff scat_coeff increased the emission by 5 xemission 1 05 Hooking a DOM Source UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DOM_SOURCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g dom will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT Note that you can hook multiple discrete ordinate source term functions to your model See Section 6 2 5 Hooking DEFINE DOM SOURCE UDFs for details 2 3 6 DEFINE DOM SPECULAR REFLECTIVITY
591. se volatiles char and ash left cf cf Gnp mpo vf 1 1 vf mp mp0 return 1 0 return 1 0 Hooking a DPM Material Property UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_PROPERTY is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Create Edit Materials dialog box in ANSYS FLUENT See Section 6 4 9 Hooking DEFINE_DPM_PROPERTY UDFs for details on how to hook your DEFINE_DPM_PROPERTY UDF to ANSYS FLUENT 2 5 10 DEFINE_DPM_SCALAR_UPDATE Description You can use DEFINE_DPM_SCALAR_UPDATE to update scalar quantities every time a parti cle position is updated The function allows particle related variables to be updated or integrated over the life of the particle Particle values can be stored in an array associ ated with the Tracked_Particle accessed with the macro P_USER_REAL p i Values calculated and stored in the array can be used to color the particle trajectory During ANSYS FLUENT execution the DEFINE DPM _SCALAR_UPDATE function is called at the start of particle integration when initialize is equal to 1 and then after each time step for the particle trajectory integration Release 12 0 ANSYS Inc January 26 2009 2 1 89 DEFINE Macros Usage DEFINE DPM SCALAR UPDATE name c t initialize p Argument Type
592. se models 3 64 mesh definitions 1 8 ZERO_COMPUTE_NODE_P 7 17 zone ID 1 9 3 29 3 31 3 77 zones definition of 1 9 ID 3 29 Index 18 Release 12 0 ANSYS Inc January 26 2009
593. se you have the added benefit of specifying UDFs on a per phase basis in both fluid and solid zones Additionally you can specify a UDF for each source term you define for a given scalar equation as well as boundary conditions on wall inflow and outflow boundaries Diffusion Coefficient UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply a unique user defined function UDF for isotropic and anisotropic diffusivity for both fluid and solid materials Recall that ANSYS FLUENT computes the diffusion coefficient in the UDS equation Isotropic diffusivity UDFs are defined using the DEFINE_DIFFUSIVITY macro Section 2 3 3 DEFINE_DIFFUSIVITY and anisotropic coefficients UDFs are defined using DEFINE ANISOTROPIC DIFFFUSIVITY Section 2 7 2 DEFINE ANISOTROPIC DIFFUSIVITY Additional pre defined macros that you can use when coding UDS functions are provided in Section 3 2 8 User Defined Scalar UDS Transport Equation Macros Release 12 0 ANSYS Inc January 26 2009 2 225 DEFINE Macros Flux UDFs For each of the N scalar equations you have specified in your ANSYS FLUENT model using the User Defined Scalars dialog box you can supply a unique user defined function or UDF for the advective flux term Recall that ANSYS FLUENT computes the flux in the UDS equation UDS Flux UDFs are defined using the DEFINE_UDS_FLUX macro Section 2 7 3 DEFINE_U
594. sition such that w x 10 4Yxsin26 178t x gt 0 02 2 6 3 wyr 0 x lt 0 02 2 6 4 where w x is the y component of the angular velocity at a position x The node position is updated based on rt P xr At 2 6 5 where Q is the angular velocity and 7 is the position vector of a node on the dynamic zone POR OC AA oo o kkk kk kkk kkk kkk kkk node motion based on simple beam deflection equation compiled UDF BER ooo o kk k kkk kkk kkk include udf h DEFINE_GRID_MOTION beam domain dt time dtime Thread tf DT_THREAD dt face_t f Node v real NV_VEC omega NV_VEC axis NV_VEC dx real NV_VEC origin NV_VEC rvec real sign int n set deforming flag on adjacent cell zone SET_DEFORMING_THREAD_FLAG THREAD_TO tf sign 5 0 sin 26 178 time Message time f omega f n time sign NV_S omega 0 0 NV_D axis 0 0 1 0 0 0 Release 12 0 ANSYS Inc January 26 2009 2 219 DEFINE Macros NV_D origin 0 0 0 0 0 152 begin_f_loop f tf f_node_loop f tf n t v F_NODE f tf n update node if x position is greater than 0 02 and that the current node has not been previously visited when looping through previous faces if NODE_X v gt 0 020 amp amp NODE_POS_NEED_UPDATE v indicate that node position has been update so that it s not updated more than once NODE_POS_UPDATED v omega 1 sign pow NODE_
595. solved see below MOLECON Pollut SPE molar concentration of species specified by SPE see below NULLIDX Pollut_Par SPE TRUE if the species specified by SPE doesn t exist in ANSYS FLUENT case i e in the Species dialog box ARRH Pollut K Arrhenius rate calculated from the constants specified by K see below POLLUT_FRATE Pollut production rate of the pollutant species being solved POLLUT_RRATE Pollut reduction rate of the pollutant species being solved POLLUT_QRATE Pollut quasi steady rate of N20 formation if the quasi steady model is used POLLUT_FLUCTDEN Pollut fluctuating density value or if no PDF model is used mean density at a given cell POLLUT_FLUCTTEM Pollut fluctuating temperature value or if no PDF model is used mean temperature at a given cell POLLUT_FLUCTYI Pollut SPE fluctuating mass fraction value or if no PDF model is used mean mass fraction at a given cell of the species given by index SPE POLLUT_CTMAX Pollut_Par upper limit for the temperature PDF integration see below i Pollut_Par is a pointer to the Pollut Parameter data structure that con tains auxiliary data common to all pollutant species and NOx is a pointer to the NOx_Parameter data structure that contains data specific to the NO model 3 40 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros e POLLUT_EQN Pollut_Par returns the index of the pollutant equation currently being
596. sorption coefficient scattering coefficient laminar flow speed rate of strain speed of sound function user defined mixing law for mixture materials density viscosity thermal conductivity scattering phase function solar intensity mass source momentum source energy source turbulence kinetic energy source turbulence dissipation rate source species mass fraction source user defined scalar source P1 radiation model source SO formation rate and upper limit for temperature PDF specific heat and sensible enthalpy surface reaction rate transition correlation numbers turbulent premixed source turbulent Schmidt number turbulent viscosity volume reaction rate wall function DEFINE_PROPERTY DEF INE_PROPERTY DEFINE PROPERTY DEFINE PROPERTY DEFINE_PROPERTY DEF INE_PROPERTY DEFINE _SCAT_PHASE_ FUNC DEFINE_SOLAR_INTENSITY DEFINE_SOURCE DEFINE_SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE_SOURCE DEF INE_SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE_SOX_RATE DEF INE_SPECIFIC_HEAT DEFINE _SR_RATE DEFINE_TRANS DEF INE_TURB_PREMIX_ SOURCE DEFINE_TURB_SCHMIDT DEF INE_TURBULENT_ VISCOSITY DEF INE_VR_RATE DEFINE _WALL_FUNCTIONS Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Create Edit Materials Radiation Model cell zone condition cell zone condition cell zone condition cell zone condition cell zone con
597. source case and data files so that all of the compute nodes in the cluster can see it To share the working folder open Windows Explorer and browse to the folder right click on the working folder select Sharing and Security from the menu click Share this folder and click OK 2 For UNIX Linux start ANSYS FLUENT from the directory that contains your case data and UDF source files For Windows start ANSYS FLUENT using FLUENT Launcher being sure to specify the folder that contains your case data and UDF source files in the Working Directory text box in the General Options tab 3 Read or set up your case file 4 Interpret the UDF using the Interpreted UDFs dialog box Figure 4 2 1 Define gt User Defined Functions Interpreted Interpreted UDFs Source File Name imywork udfexample c Browse CPP Command Name cpp Stack Size a 10000 B C Display Assembly Listing Cluse Contributed CPP Figure 4 2 1 The Interpreted UDFs Dialog Box Release 12 0 ANSYS Inc January 26 2009 4 3 Interpreting UDFs a Indicate the UDF source file you want to interpret by clicking the Browse button This will open the Select File dialog box Figure 4 2 2 Select File O mywork E udexampie c My Recent Documents kot on LEBKTHOMP UDF Source File udfexample c b My Network Files
598. spaces between the macro e g DEFINE_PROFILE and the first parenthesis of the arguments as this will cause an error in Windows Fal Do not include a DEFINE macro statement e g DEFINE PROFILE within a comment in your source code This will cause a compilation error 2 2 General Purpose DEFINE Macros The DEFINE macros presented in this section implement general solver functions that are independent of the model s you are using in ANSYS FLUENT Table 2 2 1 provides a quick reference guide to these DEFINE macros the functions they are used to define and the dialog boxes where they are activated or hooked to ANSYS FLUENT Definitions of each DEFINE macro are contained in udf h can be found in Appendix B e Section 2 2 1 DEFINE_ADJUST e Section 2 2 2 DEFINE_DELTAT e Section 2 2 3 DEFINE_EXECUTE_AT_END e Section 2 2 4 DEFINE EXECUTE_AT_EXIT e Section 2 2 5 DEFINE_EXECUTE_FROM_GUI e Section 2 2 6 DEFINE_EXECUTE_ON_LOADING e Section 2 2 7 DEFINE_EXECUTE_AFTER_CASE DATA e Section 2 2 8 DEFINE_INIT e Section 2 2 9 DEFINE_ON_DEMAND e Section 2 2 10 DEFINE RW_FILE Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Table 2 2 1 Quick Reference Guide for General Purpose DEFINE Macros Function DEFINE Macro Dialog Box Activated In manipulates variables time step size for time dependent solutions executes at end of iteration executes at end of an ANSYS FLUENT
599. specific_heat Returns specific heat given T and rho double RKEO0S_specific_heat double temp double density int i double delta_Cp press v dvdt dadt double afun a0 i pow tcrit i temp nrk i press RKEOS_pressure temp density i v 1 density dvdt RKEOS_dvdt temp density i dadt nrk i afun temp delta_Cp press dvdt rgas i dadt 1 nrk i b0 i log v b0 i v afun 1 4 nrk i dvdt v v b0 i return RKEOS_Cp_ideal_gas temp i t delta_Cp J Kg K FUNCTION RKEOS_enthalpy Returns specific enthalpy given T and rho double RKEOS_enthalpy double temp double density int i double delta_h press v double afun a0 i pow tcrit i temp nrk i press RKEOS_pressure temp density i v 1 density delta_h press v rgas i xtemp afun 1 nrk i b0 i log v b0 i v return H_REF RKEOS_H_ideal_gas temp i delta_h J Kg FUNCTION RKEOS_entropy Returns entropy given T and rho Release 12 0 ANSYS Inc January 26 2009 8 91 Examples double RKEOS_entropy double temp double density int i double delta_s v v0 dadt cp_integral double afun a0 i pow tcrit i temp nrk i cp_integral cp 0 i log t
600. ssure will be updated every iteration After 300 time steps or 15 periods are complete you can examine the pressure and velocity magnitude across the pressure outlet To collect this information during the calculation open the Surface Monitor dialog box Figure 8 2 9 before beginning the calculation Release 12 0 ANSYS Inc January 26 2009 8 21 Examples gt UA l Create Surface Monitors Surface Monitor Name Report Type monitor 1 4rea Weighted Average Field Variable Pressure Options Print to Console L Plot Static Pressure window Surfaces 2 a centerline Curves ji Axes E its larkas Write ressure inlet 4 File Name monitor 1 out symmetry 2 x Axis Flow Time Get Data Every a 1 S Time Step Figure 8 2 9 The Surface Monitor Dialog Box The Surface Monitor dialog box will display the default settings You can rename the surface monitor by entering monitor 1 in the Name text box Then set the parameters in the Options group box Enable Print to Console to see the changing values of the selected quantity in the console Enable Plot so that the selected quantity will be plotted as the calculation proceeds Enable Write so that the information will be written to a file which will be given the name you enter in the File Name text box monitor 1 out Select Flow Time from the X Axis drop down list and select Time
601. st create two build folders for each parallel version of the solver two for the 3D version two for the 2D double precision version etc regardless of the number of compute nodes 6 Copy user_nt udf from path ANSYS Inc v120 fluent fluent12 0 src to all the version subfolders you have made e g Libudf ntx86 3d Note that path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and x is replaced by the appropriate number for the release e g 9 for fluent12 0 9 7 Copy makefile_nt udf from path ANSYS Inc v120 fluent fluent12 0 rt src to all the version subfolders you have made e g libudf ntx86 3d and rename it makefile Note that path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and x is replaced by the appropriate number for the release e g 9 for fluent12 0 9 Release 12 0 ANSYS Inc January 26 2009 5 11 Compiling UDFs UNIX and Linux Systems For compiled UDFs on UNIX systems two ANSYS FLUENT files are required to build your shared UDF library makefile udf and makefile udf2 The file makefile has a user modifiable section that allows you to specify source file parameters The procedure below outlines steps that you need to follow in order to set up the directory structure required for the shared library 5 12 In your working directory make a directory that will store your UDF library e
602. stom particle surface reaction for the multiple surface reactions particle model During ANSYS FLUENT execution the same UDF is called sequentially for all particle surface reactions so DEFINE_PR_ RATE can be used to define custom reaction rates for a single reaction or for multiple reactions The volumetric and wall surface reactions are not affected by the definition of this macro and will follow the designated rates Note that a DEFINE_PR_RATE UDF is not called with the coupled solution option so you will need to disable the Coupled Heat Mass Solution option in the Discrete Phase Model dialog box when using it The auxiliary function zbrent_pr_rate which is provided below can be used when there is no analytical solution for the overall particle reaction rate 2 58 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Usage DEFINE PR_RATE name c t r mw ci p sf dif_index cat_index rr Argument Type symbol name cell tc Thread t Reaction r real mw real ci Tracked_Particle p real sf int dif_index int cat_index real rr Function returns void Description UDF name Cell index of current particle Pointer to cell thread for particle Pointer to data structure that represents the current reaction Pointer to array containing gaseous and surface species molecular weights Pointer to array containing gas partial pressures Pointer to Tracked_Particle data structure that contains
603. straight on to the host if I_AM_NODE_ZERO_P compute_node_loop_not_zero pe PRF_CRECV_INT pe amp size 1 pe array real malloc size sizeof real PRF_CRECV_REAL pe array size pe PRF_CSEND_INT node_host amp size 1 myid PRF_CSEND_REAL node_host array size myid free char array endif RP_NODE if RP_HOST compute_node_loop pe only acts as a counter in this loop Receive data sent by each node and write it out to the file PRF_CRECV_INT node_zero amp size 1 node_zero array real malloc size sizeof real PRF_CRECV_REAL node_zero array size node_zero 7 42 Release 12 0 ANSYS Inc January 26 2009 7 9 Writing Files in Parallel for i 0 i lt size i fprintf fp g n arraylil free array endif RP_HOST if RP_NODE SERIAL or HOST fclose fp Close the file that was only opened if on SERIAL or HOST Message Done n endif Release 12 0 ANSYS Inc January 26 2009 7 43 Parallel Considerations 7 44 Release 12 0 ANSYS Inc January 26 2009 Chapter 8 Examples This chapter provides examples of UDFs that range from simple to complex It begins with a step by step process that takes you through the seven basic steps of programming and using a UDF in ANSYS FLUENT Some examples for commonly used applications are subsequently presented e Section 8 1 Step By Step UDF Example e Section 8 2
604. t F_UDSI f t 0 F_VOF f t end_f_loop f t DEF INE_ON_DEMAND store_gradient Domain domain cell_t c Thread t domain Get_Domain 1 Fill the UDM with magnitude of gradient thread_loop_c t domain begin_c_loop c t C_UDMI c t 0 NV_MAG C_UDSI_G c t 0 end_c_loop c t 3 50 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros Reserving UDM Variables Using Reserve User Memory Vars The capability of loading more than one UDF library into ANSYS FLUENT raises the possibility of user defined memory UDM clashes If for example you want to use one UDF library that has a fixed 2D magnetic field stored in User Memory 0 and User Memory 1 and you want to use another UDF library that models the mass exchange between phases using User Memory 0 for the exchange rates and these two libraries are loaded at the same time then the two models are going to interfere with each other s data in User Memory 0 To avoid data contention problems ANSYS FLUENT has a macro that will allow a UDF library to reserve UDM locations prior to usage Note that there are other methods you can use within UDFs to hardcode the offset for UDMs to prevent contention that are not discussed here int Reserve_User_Memory_Vars int num The integer given as an argument to the macro num specifies the number of UDMs needed by the library The integer returned by the function is the starting point or o
605. t MIXTURE _mv molecular_weight MIXTURE_speed_of_sound speed_of_sound MIXTURE_viscosity viscosity MIXTURE_thermal_conductivity thermal_conductivity MIXTURE_rho_t drho dT const p MIXTURE_rho_p drho dp const T MIXTURE_enthalpy_t dh dT const p MIXTURE_enthalpy_p dh dp const T MIXTURE_enthalpy_prime enthalpy Release 12 0 ANSYS Inc January 26 2009 8 93 Examples 8 94 Release 12 0 ANSYS Inc January 26 2009 Appendix A A 1 C Programming Basics This chapter contains an overview of C programming basics for UDFs e Section A 1 e Section A 2 e Section A 3 e Section A 4 e Section A 5 e Section A 6 e Section A 7 e Section A 8 e Section A 9 e Section A 10 e Section A 11 e Section A 12 e Section A 13 e Section A 14 e Section A 14 e Section A 15 Introduction Introduction Commenting Your C Code C Data Types in ANSYS FLUENT Constants Variables User Defined Data Types Casting Functions Arrays Pointers Control Statements Common C Operators C Library Functions Macro Substitution Directive Using define File Inclusion Directive Using include Comparison with FORTRAN This chapter contains some basic information about the C programming language that may be helpful when writing UDFs in ANSYS FLUENT It is not intended to be used as a primer on C and assumes that you are an experienced programmer in C There are
606. t Tmax for the integration of the temperature PDF for each cell Note that this UDF does not alter the internally calculated SO rate See Section 3 2 7 SO Macros for details about the SO macro POLLUT_CTMAX used in this UDF POR ooo oo o k A A I A KK aK aK ak k k 4 4 4 k UDF example of User Defined Tmax value 2 1 10 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Arguments char sox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the SOx rate is to be applied Pollut_Cell Pollut Pointer to Pollut_Cell structure Pollut_Parameter Pollut_Par Pointer to Pollut_Parameter structure SOx_Parameter SOx Pointer to S0x_Parameter structure ANSYS FLUENT Version 12 0 or later FOO RK RK a ak a kk ak ak include udf h int ud_sox_do_once 1 enum CELL_TMAX 0 N_REQUIRED_UDM Compute assign Tmax at each cell real ud_eval_cell_tmax cell_t c Thread t real tmax 0 Compute cell based Tmax value tmax 1 1 C_T c t This is only an example return tmax DEFINE_SOX_RATE user_sox c t Pollut Pollut_Par SOx Assign cell based Tmax value POLLUT_CTMAX Pollut_Par ud_eval_cell_tmax c t Release 12 0 ANSYS Inc January 26 2009 2 1 11 DEFINE Macros POLLUT_CTMAX Pollut_Par C_UDMI c t CELL_TMAX DEF INE_ON_DEMAND init_tmax Domain domai
607. t initializes particles on a surface injection due to a surface reaction BOO E k k kkk kkk k kkk k kkk kkk k kkk k kk k kkk k kkk kkk k kkk k k Kk kkk k kkk 2k KK k KKK a include udf h include surf h RP_CELL and RP_THREAD are defined in surf h define REACTING_SURFACE_ID 2 define MW_H2 2 define STOIC_H2 1 ARRHENIUS CONSTANTS define PRE_EXP 1e 15 define ACTIVE 1e 08 define BETA 0 0 real arrhenius_rate real temp return PRE_EXP pow temp BETA exp ACTIVE UNIVERSAL_GAS_CONSTANT temp Y Species numbers Must match order in ANSYS FLUENT dialog box define HF 0 Reaction Exponents define HF_EXP 2 0 Reaction Rate Routine used in UDF real reaction_rate cell_t c Thread cthread real mw real yil Note that all arguments in the reaction_rate function call in your c source file MUST be on the same line or a compilation error will occur real concenHF C_R c cthread yi HF mw HF return arrhenius_rate C_T c cthread pow concenHF HF_EXP J 2 1 78 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros real contact_area cell_t c Thread t int s_id int n DEFINE_DPM_INJECTION_INIT init_bubbles I int count i real area mw MAX_SPE_EQNS yi MAX_SPE_EQNS MAX_SPE_EQNS is an ANSYS FLUENT constant in materials h Particle p cell_t cell Thread cthread Material mix sp Message I
608. t number to the solver 2 1 24 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example The following example sets Sc to be inversely proportional to the species index Hence the first species in the materials list will have the smallest turbulent diffusion and the last species will have the largest turbulent diffusion include udf h DEFINE_TURB_SCHMIDT udf_sct c t i return 1 real it 1 Hooking a Turbulent Schmidt Number UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_TURB_SCHMIDT is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g udf_sct in the above example will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT See Section 6 2 25 Hooking DEFINE_TURB_SCHMIDT UDFs for details 2 3 26 DEFINE_TURBULENT_VISCOSITY Description You can use DEFINE_TURBULENT_VISCOSITY to specify a custom turbulent viscosity func tion for the Spalart Allmaras k e and k w turbulence models for single phase applica tions In addition for 3d versions of ANSYS FLUENT you can specify a subgrid scale turbulent viscosity UDF for the large eddy simulation model For Eulerian multiphase flows turbulent viscosity UDFs can be assigned on a per phase basis and or to the mixture depending on the turbulence model See Table 2 3 6 for deta
609. t real origin 3 0 0 0 0 0 0 static const real axis 3 0 0 0 0 1 0 diffusivities in radial tangential and axial directions static const real diff 3 1 0 0 01 0 01 DEFINE_ANISOTROPIC_DIFFUSIVITY cyl_ortho_diff c t i dmatrix real x 3 3 principal direction matrix for cell in cartesian coords real xcent ND_ND real R C_CENTROID xcent c t NV_VV x 0 xcent origin if RP_3D NV_V x 2 axis endif if RP_3D R NV_DOT x 0 x 2 NV_VS x 0 x 2 R endif R NV_MAG x 0 if R gt 0 0 NV_S x 0 R if RP_3D N3V_CROSS x 1 x 2 x 0 else 2 228 Release 12 0 ANSYS Inc January 26 2009 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros x 1 0 x 0 1 x 1 1 x 0 0 endif dmatrix is computed as xT diff x dmatrix 0 0 diff 0 x 0 0 x 0 0 diff 1 x 1 0 x 1 0 if RP_3D diff 2 x 2 0 x 2 0 endif dmatrix 1 1 diff 0 x 0 1 x 0 1 diff 1 x 1 1 x 1 1 if RP_3D diff 2 x 2 1 x 2 1 endif dmatrix 1 0 diff 0 x 0 1 x 0 0 diff 1 x 1 1 x 1 0 if RP_3D diff 2 x 2 1 x 2 0 endif dmatrix 01 11 dmatrix 1 0 if RP_3D dmatrix 2 2 diff 0 x 0 2 x 0 2 diff 1 x 1 2 x 1 2 diff 2 x 2 2 x 2 2 dmatrix 0 2 ditt 0 x 0 0 x 0 2 diff 1 x
610. t time ca half in_cyn_ca_period 2 0 quart in_cyn_ca_period 4 0 time DYNAMESH_CURRENT_TIME ca TIME_TO_ABSOLUTE_CRANK_ANGLE time temp int ca half abs_ca ca temp half Release 12 0 ANSYS Inc January 26 2009 2 215 DEFINE Macros lh controls the layering height if abs_ca lt quart lh 0 5 abs_ca quart 0 8 else lh 0 5 half abs_ca quart 0 8 Hooking a Variable Cell Layering Height UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DYNAMIC_ZONE_PROPERTY is compiled as described in Chapter 5 Compiling UDFs the name of the argument that you sup plied as the first DEFINE macro argument will become visible in the Dynamic Mesh Zones dialog box in ANSYS FLUENT See Section 6 5 2 Hooking DEFINE_DYNAMIC_ZONE_PROPERTY UDFs for details on how to hook your DEFINE_DYNAMIC_ZONE_PROPERTY UDF to ANSYS FLUENT 2 6 3 DEFINE_GEOM Description You can use DEFINE_GEOM to specify the geometry of a deforming zone By default ANSYS FLUENT provides a mechanism for defining node motion along a planar or cylindrical surface When ANSYS FLUENT updates a node on a deforming zone e g through spring based smoothing or after local face re meshing the node is repositioned by calling the DEFINE_GEOM UDF Note that UDFs that are defined using DEFINE_GEOM can only be executed as compiled UDFs Usage DEFINE_GEOM name d dt position
611. t velocity RG vector C_V_RG c t cell_t c Thread t velocity RG vector C_W_RG c t cell_t c Thread t velocity RG vector CT RG c 6 cell t c Thread t temperature RG vector CH RG c t cell _t c Thread t enthalpy RG vector C_NUT_RG c t cell_t c Thread t turbulent viscosity for Spalart Allmaras RG vector C_K_RG c t cell_t c Thread t turbulent kinetic energy RG vector C DRG c t cell t c Thread t turbulent kinetic energy dissipation rate RG vector C_YI_RG c t i cell_t c Thread t int i species mass fraction RG vector note int i is species index Note that you can access vector components by using the integer index i for each macro listed in Table 3 2 10 For example C_T_RG c t Ci will access a component of the temperature reconstruction gradient vector Release 12 0 ANSYS Inc January 26 2009 3 15 Additional Macros for Writing UDFs C_P_RG can be used in the pressure based solver only when the second order discretization scheme for pressure is specified i C_YI_RG can be used only in the density based solver As stated previously the availability of reconstruction gradient variables is affected by your solver selection which models are turned on the setting for the spatial discretization and whether the temporary solver memory is freed To make it easy for you to verify which reconstruction gradient variables are available for your particular case and data files a UDF named showgrad c h
612. tal_area if you don t exclude the host this operation will result in a division by zero and error Remember that host has no data so its total will be zero endif You will need to use the if RP_NODE directive when you want to exclude compute nodes from operations for which they do not have data 7 12 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs Below is a list of parallel compiler directives and what they do Note that if either RP_HOST or RP_NODE are true then PARALLEL is also true DOR k kkk k kk k kkk k kkk I k kk k kkk k KKK k kK k k Kk A 2k 2 2k K 2k 26 2k 2k 2k 2k 2k 2k 2 2k kK k Compiler Directives DCR OC OO I k I kkk k kkk k kkk kkk k 2k 2 2k kkk k kkk k kkk kkk if RP_HOST only host process is involved endif if RP_NODE only compute nodes are involved endif if PARALLEL both host and compute nodes are involved but not serial equivalent to if RP_HOST RP_NODE endif CORO OOO BC kkk kkk k kkk k kkk kkk k kkk k kkk k kkk k Negated forms that are more commonly used paaa aaao ooo ooo oo o ICA A A A KK 1 21 21 21 A A A A A KKK kkk kk if RP_HOST either serial or compute node process is involved endif if RP_NODE either serial or host process is involved endif if PARALLEL only serial process is involved endif The following simple UDF shows the use of compiler directives The adjust function is us
613. tc return sum Example 3 Surface Tension Coefficient UDF DEFINE PROPERTY can also be used to define a surface tension coefficient UDF for the multiphase VOF model The following UDF specifies a surface tension coefficient as a quadratic function of temperature The source code can be interpreted or compiled in ANSYS FLUENT DRO OG FK 2K 2K K FK 2K 2K FK FK 2K K FK 2K 2K A FK FK RK FK 2K 2K K 2K 24 2k FK 2k 2K 2k FK 2k 2K 2k FK 2k ok Surface Tension Coefficient UDF for the multiphase VOF Model ROCCO ooo o kkk k kkk 4 24 243k 3k include udf h DEFINE_PROPERTY sfc c t 2 92 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros real T C_T c t return 1 35 0 004 T 5 0e 6 T T FA Note that surface tension UDFs for the VOF and Mixture multiphase mod els are both hooked to ANSYS FLUENT in the Phase Interaction dialog box but in different ways For the VOF model the function hook is located in the Surface Tension tab in the dialog box For the Mixture model however the function hook is located in the Mass tab and will become visible upon selecting the Cavitation option Example 4 Density Function for Compressible Liquids Liquid density is not a constant but is instead a function of the pressure field In order to stabilize the pressure solution for compressible flows in ANSYS FLUENT an extra term related to the speed of sound is needed in the pressure correction equation Conseq
614. te node 0 to host char string int string_length real vel ND_ND node_to_host_string string string_length node_to_host_real vel ND_ND node_to_host macros do not need to be protected by compiler directives e g if RP_NODE since they automatically do the following e send the variable value if the node is compute node 0 and the function is compiled as a node version e do nothing if the function is compiled as a node version but the node is not compute node 0 e receive and set variables if the function is compiled as the host version e do nothing for the serial version 7 16 Release 12 0 ANSYS Inc January 26 2009 7 5 Macros for Parallel UDFs The most common usage for this set of macros is to pass global reduction results from compute node 0 to the host process In cases where the value that is to be passed is computed by all of the compute nodes there must be some sort of collection such as a summation of the data from all the compute nodes onto compute node 0 before the single collected summed value can be sent Refer to the example UDF in Section 7 8 Parallel UDF Example for a demonstration of usage and Section 7 5 4 Global Reduction Macros for a full list of global reduction operations 7 5 3 Predicates There are a number of macros available in parallel ANSYS FLUENT that expand to logical tests These logical macros referred to as predicates are denoted by the suffix P and can be used
615. ted with its cells or faces in a set of arrays For example pressure is stored in an array and the pressure for cell c is obtained by accessing element c of that array Storage for exterior cell and face data occurs at the end of every thread data array as shown in Figure 7 2 3 7 3 Parallelizing Your Serial UDF ANSYS FLUENT s serial solver contains Cortex and only a single ANSYS FLUENT process The parallel solver on the other hand contains three types of executable Cortex host and compute node or simply node for short When ANSYS FLUENT runs in parallel an instance of Cortex starts followed by one host and n compute nodes thereby giving a total of n 2 running processes For this reason when you are running in parallel you will need to make sure that your function will successfully execute as a host and a node process At first it may appear that you should write three different versions of your UDF one for serial host and node Good programming practice however would suggest that you write a single UDF that when compiled can execute on any of the three versions This process is referred to in this manual as parallelizing your serial UDF You can do this by adding special macros for parallel as well as compiler directives to your UDF as described below Compiler directives e g if RP_NODE RP_HOST PARALLEL and their Release 12 0 ANSYS Inc January 26 2009 7 9 Parallel Considerations THREAD_N_ELEM
616. ter define DEFINE_DYNAMIC_ZONE_PROPERTY name dt height void name Dynamic_Thread dt real height define DEFINE_GEOM name d dt position void name Domain d Dynamic_Thread dt real position define DEFINE_GRID_MOTION name d dt time dtime void name Domain d Dynamic_Thread dt real time real dtime define DEFINE_SDOF_PROPERTIES name properties dt time dtime void name real properties Dynamic_Thread dt real time real dtime Release 12 0 ANSYS Inc January 26 2009 B 5 DEFINE Macro Definitions B 5 Discrete Phase Model DEFINE Macros The following definitions for DPM DEFINE macros see Section 2 5 Discrete Phase Model DPM DEFINE Macros are taken from the dpm h header file Note that dpm h is included in the udf h header file define DEFINE_DPM_BC name p t f normal dim int name Tracked_Particle p Thread t face_t f real normal int dim define DEFINE_DPM_BODY_FORCE name p i real name Tracked_Particle p int i define DEFINE_DPM_DRAG name Re p real name real Re Tracked_Particle p define DEFINE_DPM_EROSION name p t f normal alpha Vmag mdot void name Tracked_Particle p Thread t face_t f real normal real alpha real Vmag real mdot define DEFINE_DPM_HEAT_MASS name p Cp hgas hvap cvap_surf dydt dzdt void name Tracked_Particle p real Cp real hgas real hvap real cvap_surf real dydt dpms_t dzdt define D
617. the Run Calculation task page Ma Run Calculation Select Adaptive in the Time Stepping Method drop down list and click the Settings button to open the Adaptive Time Step Settings dialog box Figure 6 1 3 Release 12 0 ANSYS Inc January 26 2009 6 3 Hooking UDFs to ANSYS FLUENT Adaptive Time Step Settings Ending Time 5 User Defined Time Step mydeltat libudf v Figure 6 1 3 The Adaptive Time Step Settings Dialog Box Select the function name e g mydeltat libudf in the User Defined Time Step drop down list and click OK Note that when you are using the VOF Multiphase Model you will need to select Variable as the Time Stepping Method in the Run Calculation task page and then hook the time step UDF in the Variable Time Step Setting dialog box in a similar manner to the Adaptive Time Step Settings dialog box See Section 2 2 2 DEFINE_DELTAT for details about defining DEFINE_DELTAT functions Release 12 0 ANSYS Inc January 26 2009 6 1 Hooking General Purpose UDFs 6 1 3 Hooking DEFINE_EXECUTE_AT_END UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_EXECUTE_AT_END UDF it is ready to be hooked to ANSYS FLUENT Note that you can hook multiple at end UDFs to your model if desired To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 1 4 Define
618. the Tracked_Particle data structure which contains data related to the particle being tracked Particle p Pointer to the Particle data structure where particles p are stored in a linked list Function returns void There are three arguments to DEFINE_DPM_SPRAY_COLLIDE name tp and p You supply name the name of the UDF tp and p are variables that are passed by the ANSYS FLUENT solver to your UDF When collision is enabled this linked list is ordered by the cell that the particle is currently in As particles from this linked list are tracked they are copied from the particle list into a Tracked_Particle structure 2 1 94 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros Example The following UDF named mean_spray_collide is a simple and non physical exam ple that demonstrates the usage of DEFINE_SPRAY_COLLIDE The droplet diameters are assumed to relax to their initial diameter over a specified time t_relax The droplet velocity is also assumed to relax to the mean velocity of all droplets in the cell over the same time scale PRR AA A oo o kkk k k kkk kk kkk k kkk DPM Spray Collide Example UDF EEEE EE ooo kkk k kkk kkk kkk kkk kkk include udf h include dpm h include surf h DEFINE_DPM_SPRAY_COLLIDE mean_spray_collide tp p non physical collision UDF that relaxes the particle velocity and diameter in a cell to the mean over the specified time scal
619. the mixture domain and provides the pointers of the phase level cell threads asso ciated with each mixture level thread This is nearly identical to the thread_loop_c macro Section 3 3 Looping Over Cell Threads in a Domain thread_loop_c when applied to the mixture domain The difference is that in addition to stepping through each cell thread the macro also returns a pointer array pt that identifies the corre sponding phase level threads The pointer to the cell thread for the ith phase is pt i where i is the phase_domain_index pt i can be used as an argument to macros re quiring the phase level thread pointer phase_domain_index can be retrieved using the PHASE_DOMAIN_INDEX macro See Section 3 3 2 Phase Domain Index PHASE_DOMAIN_INDEX for details 3 62 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros Thread pt Thread cell_threads Domain mixture_domain mp_thread_loop_c cell_threads mixture_domain pt The variable arguments to mp_thread_loop_c are cell_threads mixture_domain and pt cell_threads is a pointer to the cell threads and mixture_domain is a pointer to the mixture level domain pt is an array pointer whose elements contain pointers to phase level threads mixture domain is automatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE_ADJUST and your UDF is hooked to the mixture If mixture_domain is
620. the pressure based and the density based solver The quantities that are returned are available only if the corresponding physical model is active For example species mass fraction is available only if species transport has been enabled in the Species Model dialog box in ANSYS FLUENT Definitions for these macros can be found in the referenced header file e g mem h Cell Centroid C_CENTROID The macro listed in Table 3 2 3 can be used to obtain the real centroid of a cell C_CENTROID finds the coordinate position of the centroid of the cell c and stores the coordinates in the x array Note that the x array is always one dimensional but it can be x 2 or x 3 depending on whether you are using the 2D or 3D solver Table 3 2 3 Macro for Cell Centroids Defined in metric h Macro Argument Types Outputs C_CENTROID x c t real x ND_ND cell_t c Thread t x cell centroid See Section 2 2 8 DEFINE_INIT for an example UDF that utilizes C_CENTROID Cell Volume C_VOLUME The macro listed in Table 3 2 4 can be used to obtain the real cell volume for 2D 3D and axisymmetric simulations Table 3 2 4 Macro for Cell Volume Defined in mem h Macro Argument Types Returns C_VOLUME c t cell_t c Thread t real cell volume for 2D or 3D real cell volume 2z for axisymmetric See Section 2 7 4 DEFINE_UDS_UNSTEADY for an example UDF that utilizes C_VOLUME Release 12 0 ANSYS Inc Janu
621. the pressure oscillates around the equilibrium value 101325 Pa with an amplitude of 5 Pa as expected Release 12 0 ANSYS Inc January 26 2009 8 23 Examples 101330 7 ANSYS 101329 101328 101327 101326 Area 101325 Weighted 101324 l i prestige 101322 101321 101320 Wy 0 00 1 00 2 00 3 00 4 00 5 00 6 00 7 00 8 00 9 00 10 00 Flow Time 1 D Unsteady Flow in a Tube Convergence history of Static Pressure on pressure outlet 5 in SI units Time 9 4200e 00 FLUENT 12 0 2d pbns transient Figure 8 2 11 Average Static Pressure at the Pressure Outlet Area Weighted Average Velocity Magnitude 0 00 1 00 2 00 3 00 4 00 5 00 6 00 7 00 8 00 9 00 10 00 Flow Time 1 D Unsteady Flow in a Tube Convergence history of Velocity Magnitude on pressure outlet 5 in SI unts Time 9 4200e 00 NT 12 0 2d pbns transient Figure 8 2 12 Average Velocity Magnitude at the Pressure Outlet 8 24 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples 8 2 2 Source Terms This section contains an application of a source term UD
622. the udf h File 5 1 1 Location of the udf h File UDFs are defined using DEFINE macros see Chapter 2 DEFINE Macros and the defini tions for DEFINE macros are included in udf h Consequently before you compile your source file the udf h header file will need to be accessible in your path or saved locally within your working folder The location of the udf h file is path ANSYS Inc v120 fluent fluent12 0 2 src udf h where path is the folder in which you have installed ANSYS FLUENT by default the path is C Program Files and z is replaced by the appropriate number for the release e g 9 for fluent12 0 9 i In general you should not copy udf h from the installation area The compiler is designed to look for this file locally in your current folder first If it is not found in your current folder the compiler will look in the src folder automatically In the event that you upgrade your release area but do not remove an old copy of udf h from your working folder you will not be accessing the most recent version of this file i You should not under any circumstances alter the udf h file There may be instances when will want to include additional header files in the compi lation process Make sure that all header files needed for UDFs are located in the src folder Release 12 0 ANSYS Inc January 26 2009 5 3 Compiling UDFs 5 1 2 Compilers The graphical and text interface processes for a compiled
623. these high level macros when you need to pass data between compute nodes or pass data from all of the compute nodes to compute node 0 In these cases you can use special message passing macros described in this section Note that the higher level communication macros expand to functions that perform a number of lower level message passing operations which send sections of data as single arrays from one process to another process These lower level message passing macros can be easily identified in the macro name by the characters SEND and RECV Macros that are used to send data to processes have the prefix PRF_CSEND whereas macros that are used to receive data from processes have the prefix PRF_CRECV Data that is to be sent or received can belong to the following data types character CHAR integer INT REAL and logical BOOLEAN BOOLEAN variables are TRUE or FALSE REAL variables are assigned as float data types when running a single precision version of ANSYS FLUENTand double when running double precision Message passing macros are defined in the prf h header file and are listed below message passing macros PRF_CSEND_CHAR to buffer nelem tag PRF_CRECV_CHAR from buffer nelem tag PRF_CSEND_INT to buffer nelem tag PRF_CRECV_INT from buffer nelem tag PRF_CSEND_REAL to buffer nelem tag PRF_CRECV_REAL from buffer nelem tag PRF_CSEND_BOOLEAN to buffer nelem tag PRF_CRECV_BOOLEAN from buffer nelem tag
624. they are used to define and the dialog boxes in which they are activated in ANSYS FLUENT Definitions of each DEFINE macro are listed in the udf h header file see Appendix C Appendix B contains a list of general purpose DEFINE macros that can also be used to define UDFs for multiphase cases For example the general purpose DEFINE_PROPERTY macro is used to define a surface tension coefficient UDF for the multiphase VOF model See Section 2 3 16 DEFINE PROPERTY UDFs for details e Section 2 4 1 DEFINE_CAVITATION_RATE Section 2 4 2 DEFINE EXCHANGE PROPERTY Section 2 4 3 DEFINE_HET_RXN_RATE Section 2 4 4 DEFINE_MASS_TRANSFER Section 2 4 5 DEFINE_VECTOR_EXCHANGE_PROPERTY Release 12 0 ANSYS Inc January 26 2009 2 1 35 DEFINE Macros Table 2 4 1 Quick Reference Guide for Multiphase DEFINE Macros Model Function DEFINE Macro Dialog Box Activated VOF mass transfer DEFINE_MASS_TRANSFER Phase Interaction heterogeneous DEFINE_HET_RXN_RATE Phase Interaction reaction rate Mixture mass transfer DEFINE_MASS_TRANSFER Phase Interaction drag coefficient DEFINE EXCHANGE PROPERTY Phase Interaction slip velocity DEFINE _VECTOR_EXCHANGE_ Phase Interaction PROPERTY cavitation rate DEFINE CAVITATION RATE User Defined Function Hooks heterogeneous DEFINE HET RXN_RATE Phase Interaction reaction rate Eulerian mass transfer DEFINE_MASS_TRANSFER Phase Interaction heat transfer DEFINE_EXCHANGE_PROPERTY
625. tion Time s n if NULLP p return X y r P_POS p 0 P_POS p 1 sqrt SQR x SQR y par_fprintf fp d hd he A Af hf KE he he hf he AE n P_INJ_ID P_INJECTION p p gt part_id P_TIME p r P_VEL p 0 P_VEL p 1 P_VEL p 2 P_DIAM p P_N p P_T p P_INIT_DIAM p p gt time_of_birth endif if REMOVE_PARTICLES p gt stream_index 1 endif Release 12 0 ANSYS Inc January 26 2009 2 1 85 DEFINE Macros Hooking a DPM Output UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_OUTPUT is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Sample Trajectories dialog box in ANSYS FLUENT See Section 6 4 8 Hooking DEFINE_DPM_OUTPUT UDF s for details on how to hook your DEFINE_DPM_OUTPUT UDF to ANSYS FLUENT 2 5 9 DEFINE_DPM_PROPERTY Description You can use DEFINE DPM PROPERTY to specify properties of discrete phase materials For example you can model the following dispersed phase properties with this type of UDF e particle emissivity e vapor pressure e vaporization temperature particle scattering factor boiling point particle viscosity particle surface tension Usage DEFINE_DPM PROPERTY name c t p Argument Type Description symbol name UDF name cellt c Index that identifies the cell
626. tion group box and enable Stiff Chemistry Solver in the Options group box e To enable the EDC model select Species Transport enable Volumetric in the Re actions group box and select Eddy Dissipation Concept in the Turbulence Chemistry Interaction group box e To enable the PDF Transport model select Composition PDF Transport and enable Volumetric in the Reactions group box e To enable the surface chemistry model select Species Transport and enable Volu metric and Wall Surface in the Reactions group box Next open the User Defined Function Hooks dialog box Figure 6 2 13 Define User Defined Function Hooks User Defined Function Hooks Initialization none Adjust none Execute at End E Read Case i none Write Case i none Read Data e Write Data none Execute at Exit none Wall Heat Flux Net Reaction Rate net rxn bud volume Reaction Rate Surface Reaction Rate Figure 6 2 13 The User Defined Function Hooks Dialog Box Release 12 0 ANSYS Inc January 26 2009 6 27 Hooking UDFs to ANSYS FLUENT Select the function name e g net_rxn libudf in the Net Reaction Rate Function drop down list and click OK See Section 2 3 11 DEFINE NET REACTION RATE for details about DEFINE NET REACTION RATE functions 6 2 12 Hooking DEFINE NOX RATE UDFs After you have compiled Chapter 5 Compiling UDFs your DEFINE NOX RATE UDF in ANSYS FLUENT the function name
627. tion name e g user_mu_t libudf from the Turbulence Viscosity drop down list under User Defined Functions in the Viscous Model dialog box and click OK See Section 2 3 26 DEFINE TURBULENT _ VISCOSITY for details about DEFINE_TURBULENT_VISCOSITY functions 6 52 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 27 Hooking DEFINE_VR_RATE UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_VR_RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 36 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first set up an appropriate reaction model in the Species Model dialog box A Seets Edit Select Species Transport from the Model list in the Species Model dialog box and enable the Volumetric option in the Reactions group box Make sure that Stiff Chemistry Solver is disabled in the Options group box and click OK Next open the User Defined Function Hooks dialog box Figure 6 2 36 Define User Defined Function Hooks Initialization Adjust Execute at End m Read Case Write Case Read Data ro Write Data Execute at Exit Wall Heat Flux Volume Reaction Rate pay yaRN ier v Figure 6 2 36 The User
628. tion of a physical property UDF It is executed as an interpreted UDF in ANSYS FLUENT Solidification via a Temperature Dependent Viscosity UDFs for properties as well as sources are called from within a loop on cells For this reason functions that specify properties are only required to compute the property for a single cell and return the value to the ANSYS FLUENT solver 8 30 Release 12 0 ANSYS Inc January 26 2009 8 2 Detailed UDF Examples The UDF in this example generates a variable viscosity profile to simulate solidification and is applied to the same problem that was presented in Section 8 2 2 Adding a Mo mentum Source to a Duct Flow The viscosity in the warm T gt 288 K fluid has a molecular value for the liquid 5 5 x10 kg m s while the viscosity for the cooler re gion T lt 286 K has a much larger value 1 0 kg m s In the intermediate temperature range 286 K lt T lt 288 K the viscosity follows a linear profile Equation 8 2 3 that extends between the two values given above u 143 2135 0 497257 8 2 3 This model is based on the assumption that as the liquid cools and rapidly becomes more viscous its velocity will decrease thereby simulating solidification Here no correction is made for the energy field to include the latent heat of freezing The C source code for the UDF is shown below The function named cell viscosity is defined on a cell using DEFINE PROPERTY Two real va
629. tion you supplied as a DEFINE macro argument will become visible and selectable in ANSYS FLUENT To hook the UDF to ANSYS FLUENT you will first need to open the Materials task page lt BWEcarlS Select the appropriate material from the Material selection list and click the Create Edit button to open the Create Edit Materials dialog box Figure 6 2 29 Create Edit Materials Name Material Type Order Materials by air fluid vi Name Chemical Formula Chemical Formula FLUENT Database User Defined Database FLUENT Fluid Materials air Properties Density kg m3 Fear 1 225 Cp Specific Heat j kg k Fa defined my_user_cp libudf Thermal Conductivity w m k pre 0 0242 Viscosity kg m s constant 1 7894e 05 v Figure 6 2 29 The Create Edit Materials Dialog Box Next select user defined from the drop down list for Cp to open the User Defined Functions dialog box Figure 6 2 30 Select the name you defined in the UDF e g my user cp libudf and click OK The name of the function will subsequently be displayed under the Cp prop erty in the Create Edit Materials dialog box See Section 2 3 21 DEFINE_SPECIFIC_HEAT for details about defining DEFINE_SPECIFIC_HEAT UDFs 6 46 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs User Defined Fu my user cp libudf
630. tions Release 12 0 ANSYS Inc January 26 2009 6 83 Hooking UDFs to ANSYS FLUENT 6 84 Hooking a Variable Cell Layering Height UDF After you have compiled your DEFINE_DYNAMIC_ZONE_PROPERTY UDF as described in Chapter 5 Compiling UDFs the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Dynamic Mesh Zones dialog box Fig ure 6 5 3 Since the DEFINE_DYNAMIC_ZONE_PROPERTY UDF is a function of time or crank angle you must make sure that you have selected Transient from the Time list in the Solver group box of the General task page before proceeding To hook the UDF to ANSYS FLUENT you will first need to enable the Dynamic Mesh option in the Dynamic Mesh task page DaN Dynamic Mesh Then enable the Layering option in the Mesh Methods list and click the Settings button to open the Mesh Methods Settings dialog box In the Layering tab select Height Based from the Options list and set the Split Factor and Collapse Factor to appropriate values Then click OK Next specify the meshing options in the Dynamic Mesh Zones dialog box Figure 6 5 3 gt OANA Create Edit Dynamic Mesh Zones Zone Names Dynamic Mesh Zones defautt interior v default interior Fluid move Type wall Stationary O Rigid Body O Deforming O User Defined Motion Attributes Geometry Definition Meshing Options Adj
631. tiphase flow For example there will be no differences between the C code for a single phase boundary profile defined using DEFINE_PROFILE and the code for a multiphase profile assuming that the function is accessing data only from the phase level domain to which it is hooked in the graphical user interface If your UDF is not explicitly passed a pointer to the thread or domain structure that it requires you will need to use a special multiphase specific macro e g THREAD_SUB_THREAD to retrieve it This is discussed in Chapter 3 Additional Macros for Writing UDFs See Appendix B for a complete list of general purpose DEFINE macros and multiphase specific DEFINE macros that can be used to define UDFs for multiphase model cases 1 10 1 Multiphase specific Data Types In addition to the ANSYS FLUENT specific data types presented in Section 1 8 Data Types in ANSYS FLUENT there are special thread and domain data structures that are specific to multiphase UDFs These data types are used to store properties and variables for the mixture of all of the phases as well as for each individual phase when a multiphase model i e Mixture VOF Eulerian is used In a multiphase application the top level domain is referred to as the superdomain Each phase occupies a domain referred to as a subdomain A third domain type the interaction domain is introduced to allow for the definition of phase interaction mechanisms When mixture p
632. titions 7 1 phase domain subdomain pointer 3 65 phase domain index 3 68 Phase Interaction dialog box 6 57 6 60 6 61 phase thread subthread pointer 3 66 phase level threads 1 17 3 67 PHASE_DOMAIN_INDEX 3 62 3 63 3 65 3 68 Release 12 0 ANSYS Inc January 26 2009 phase_domain_index 1 18 3 66 3 68 pointer array 3 62 3 67 pointers 1 11 A 8 domain 1 11 phase domain 3 66 3 68 phase thread 3 66 thread 1 11 POLLUT_CTMAX 3 40 3 41 3 43 POLLUT_EQN 3 40 3 42 POLLUT_FLUCTDEN 3 40 3 41 POLLUT_FLUCTTEM 3 40 3 41 POLLUT_FLUCTYI 3 40 3 41 POLLUT_FRATE 3 40 3 41 POLLUT_QRATE 3 40 POLLUT_RRATE 3 40 3 41 postprocessing UDF example 8 40 postprocessing UDF parallel 7 40 Prandtl number UDFs specific dissipation 2 68 temperature equation diffusion term 2 69 thermal wall function 2 70 turbulence kinetic energy 2 65 turbulent dissipation 2 64 predicates parallel UDFs 7 17 premixed combustion model UDFs source term 2 122 turbulent flame speed 2 122 Pressure Outlet dialog box 8 20 pressure outlet transient profile UDF 8 19 PRF_CRECV 7 29 PRF_CRECV_INT 7 40 PRF_CRECV_REAL 7 40 PRF_CSEND 7 29 PRF_CSEND_INT 7 40 PRF_CSEND_REAL 7 40 PRF_GIHIGH 7 18 7 20 PRF_GILOW 7 20 PRF_GISUM 7 18 7 20 PRF_GLAND 7 21 PRF_GLOR 7 21 PRF_GRHIGH 7 20 Index 13 Index PRF_GRLOW 7 20 PRF_GRSUM 7 20 PRF_GRSUM1 7 39 PRF_GSYNC 7 22 PRINCIPAL_FACE_P 7 9 7 26 7 39 printf 2 9 2 23
633. to get the complete advective term return flux Hooking a UDS Flux Function to ANSYS FLUENT After the UDF that you have defined using DEFINE_UDS_FLUX is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g my _uds_flux will become visible and selectable in the User Defined Scalars dialog box in ANSYS FLUENT See Section 6 6 2 Hooking DEFINE_UDS_FLUX UDFs for details 2 7 4 DEFINE_UDS_UNSTEADY Description You can use DEFINE_UDS_UNSTEADY to customize unsteady terms in your user defined scalar UDS transport equations See Section 9 1 User Defined Scalar UDS Trans port Equations in the separate User s Guide for details on setting up and solving UDS transport equations Usage DEFINE _UDS_UNSTEADY name c t i apu su Argument Type Description symbol name UDF name cell tc Cell index Thread t Pointer to cell thread on which the unsteady term for the user defined scalar transport equation is to be applied int i Index that identifies the user defined scalar for which the unsteady term is to be set real apu Pointer to central coefficient real su Pointer to source term Function returns void 2 234 Release 12 0 ANSYS Inc January 26 2009 2 7 User Defined Scalar UDS Transport Equation DEFINE Macros There are six arguments to DEFINE_UDS_UNSTEADY name c t i apu
634. to write the melting index at sample planes and surfaces The macro NULLP which expands to p NULL checks if its argument is a null pointer 2 1 90 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros PK kkk OC OO I FK 2K K A K FK 2K OA 3K 2K K a 2K 2k FK 2k 2K FK FK 2k K FK 2k 24 2k FK 2k 2K 2k FK 2k UDF for computing the melting index along a particle trajectory BE AAR ooo kkk kk kkk kkk kkk kkk kkk include udf h DEFINE_INIT melt_setup domain if memory for the particle variable titles has not been allocated yet do it now if NULLP user_particle_vars Init_User_Particle_Vars now set the name and label strcpy user_particle_vars 0 name melting index strcpy user_particle_vars 0 label Melting Index strcpy user_particle_vars 1 name melting index 0 strcpy user_particle_vars 1 label Melting Index 0 update the user scalar variables DEFINE_DPM_SCALAR_UPDATE melting_index cell thread initialize p cphase_state_t c amp p gt cphase if initialize this is the initialization call set P_USER_REAL p 0 contains the melting index initialize to 0 P_USER_REAL p 1 contains the viscosity at the start of a time step P_USER_REAL p 0 0 P_USER_REAL p 1 c gt mu else use a trapezoidal rule to integrate the melting index P_USER_REAL p 0 P_DT p 5 1 P_USER_REAL p 1 1 c gt mu
635. ts to DEFINE_DOM_DIFFUSE_REFLECTIVITY name t nb n_a n_b diff _ref_a diff_tran_a diff_ref_b and diff_tran_b You supply name the name of the UDF t nb n_a n_b diff_ref_a diff_tran_a diff_ref_b and diff_tran_b are variables that are passed by the ANSYS FLUENT solver to your UDF 2 36 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros Example The following UDF named user_dom_diff_ref1 modifies diffuse reflectivity and trans missivity values on both the sides of the interface separating medium a and b The UDF is called for all the semi transparent walls and prints the value of the diffuse reflectivity and transmissivity values for side a and b i Note that in the example that follows the DEFINE DOM DIFFUSE REFLECTIVITY statement is broken up into two lines for the sake of readability In your source file you must make sure that the DEFINE statement is on one line only UDF to print the diffuse reflectivity and transmissivity at semi transparent walls include udf h DEFINE_DOM_DIFFUSE_REFLECTIVITY user_dom_diff_refl t nband n_a n_b diff_ref_a diff_tran_a diff_ref_b diff_tran_b printf diff_ref_a f diff_tran_a f n diff_ref_a diff_tran_a printf diff_ref_b f diff_tran_b f n diff_ref_b diff_tran_b Hooking a Discrete Ordinates Model DOM Diffuse Reflectivity UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DOM_DIFFUSE_REFLECTI
636. uel rf ARRH Pollut K_PM rf pow Pollut_Par gt uni_R Pollut gt temp_m Pollut gt press 1 Pollut gt oxy_order rf pow MOLECON Pollut 02 Pollut gt oxy_order rf MOLECON Pollut N2 POLLUT_FRATE Pollut fxrf Release 12 0 ANSYS Inc January 26 2009 2 55 DEFINE Macros break case QUT_PDF Char Contributions must be included here break default Not used break Example 2 The following compiled UDF named nox_func_name specifies a custom maximum limit Tmax for the integration of the temperature PDF for each cell Note that this UDF does not alter the internally calculated NO rate See Section 3 2 7 NO Macros for details about the NO macro POLLUT_CTMAX used in this UDF POR COCA AAA kkk I A A kK 21 21 kkk kk 4 4 2k UDF example of User Defined Tmax value Arguments char nox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the NOx rate is to be applied Pollut_Cell Pollut Pointer to Pollut_Cell structure Pollut_Parameter Pollut_Par Pointer to Pollut_Parameter structure NOx_Parameter NOx Pointer to NOx_Parameter structure ANSYS FLUENT Version 12 0 or later FR a a a ak 2k 3k 2k 2k a 3k 2k ak 2k 2k ak ak 2 56 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros include udf h int ud_nox_do_once 1 enum CELL_TMAX 0 N_REQUIR
637. uently when you want to define a custom density function for a compressible flow your model must also include a speed of sound function Although you can direct ANSYS FLUENT to calculate a speed of sound function by choosing one of the available methods e g piecewise linear polynomial in the Create Edit Materials dialog box as a general guide line you should define a speed of sound function along with your density UDF using the formulation V5 For simplicity it is recommended that you concatenate the density and speed of sound functions into a single UDF source file The following UDF source code example contains two concatenated functions a density function named superfluid_density that is defined in terms of pressure and a custom speed of sound function named sound_speed pLa oo ooo oo kk kkk kkk kk kkk A A A kk kkk kk Density and speed of sound UDFs for compressible liquid flows For use with pressure based solver for single phase multiphase mixture or cavitation models only Note that for density function dp is the difference between a cell absolute pressure and reference pressure EEEE ooo ooo o kkk kk kkk k kkk include udf h Release 12 0 ANSYS Inc January 26 2009 2 93 DEFINE Macros define BMODULUS 2 2e9 define rho_ref 1000 0 define p_ref 101325 DEFINE_PROPERTY superfluid_density c t real rho real p dp real p_operating p_operating RP_Get_Real operating pressure p
638. ues for the erosion rate and or accretion rate and store the values at the faces in F_STORAGE_R f t SV_DPMS_EROSION and F_STORAGE_R f t SV_DPMS_ACCRETION respectively Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example The following is an example of a compiled UDF that uses DEFINE_DPM_EROSION to extend postprocessing of wall impacts in a 2D axisymmetric flow It provides additional infor mation on how the local particle deposition rate depends on the diameter and normal velocity of the particles It is based on the assumption that every wall impact leads to more accretion and therefore every trajectory is evaporated at its first wall impact This is done by first setting a DPM user scalar within DEFINE_DPM_EROSION which is then evaluated within DEFINE_DPM_LAW where P_MASS is set to zero User defined mem ory locations UDMLs are used to store and visualize the following e number of wall impacts since UDMLs were reset Resetting is typically done at the beginning of an ANSYS FLUENT session by the use of DEFINE_ON_DEMAND in order to avoid the use of uninitialized data fields Resetting prevents the addition of sampled data being read from a file e average diameter of particles hitting the wall e average radial velocity of particles Before tracing the particles you will have to reset the UDMLs an
639. ular UDF is not a practical application but has rather been designed to demonstrate the functionality It uses data from a FORTRAN derived object file to display parameters that are passed to the C function named fort_test This on demand UDF when executed from the User Defined Function Hooks dialog box displays the values of the FORTRAN parameters and the common block and common complex numbers that are computed by the UDF using the FORTRAN parameters i Note that the names of the functions and data structures have been changed from the capital form in FORTRAN e g ADDAB is changed to addab_ This name mangling is done by the compiler and is strongly system dependent Note also that functions returning complex numbers have different forms on different machine types since C can return only single values and not structures Consult your system and compiler man uals for details 5 20 Release 12 0 ANSYS Inc January 26 2009 5 4 Link Precompiled Object Files From Non ANSYS FLUENT Sources 1 In the first step of this example a FORTRAN source file named test f is compiled and the resulting object file test o is placed in the shared library folder for the ultra 2d version libudf ultra 2d The source listing for test f is shown below FORTRAN function test f compile to o file using 77 KPIC n32 0 c test f irix6 amp suns REAL 8 FUNCTION ADDAB A B C REAL A REAL 8 B REAL 8 YCOM COMPLEX ZCOM INTEGER
640. ume real variable named volume is declared globally DEFINE_ADJUST compute_volume domain code that computes volume of some zone volume If multiple source files want to use volume in their computations then volume can be declared as an external variable in a header file e g extfile h extfile h Header file that contains the external variable declaration for volume extern real volume Now another file named file2 c can declare volume as an external variable by simply including extfile h file2 c include udf h include extfile h header file containing extern declaration is included DEFINE_SOURCE heat_source c t ds eqn code that computes the per unit volume source using the total Release 12 0 ANSYS Inc January 26 2009 A 5 C Programming Basics volume computed in the compute_volume function from filel c real total_source real source source total_source volume return source A 5 3 Static Variables The static operator has different effects depending on whether it is applied to local or global variables When a local variable is declared as static the variable is prevented from being destroyed when a function returns from a call In other words the value of the variable is preserved When a global variable is declared as static the variable is file global It can be used by any function within the source file in which it is declared b
641. ument will become visible and selectable in the Set Injection Properties dialog box Figure 6 4 5 in ANSYS FLUENT To hook the UDF first set up your species transport model in the Species Model dialog box A Sets Edit Select Species Transport from the Model list and click OK Next create a particle injection in the Injections dialog box Define Injections Click Create in the Injections dialog box to open the Set Injection Properties dialog box Figure 6 4 5 Set Injection Properties Injection Name injection 0 Injection Type single Particle Type Laws O Massless O Inert Droplet O Combusting Multicomponent C Custom Material i Discrete Phase Domain particle mixture template none Point Properties Turbulent Dispersion Wet Combustion Components UDF Multiple Reactions User Defined Functions Initialization none v Heat Mass Transfer multivap libudf v Figure 6 4 5 The Set Injections Dialog Box 6 68 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs Set up the particle injection in the Set Injection Properties dialog box being sure to select Multicomponent in the Particle Type group box Then click the UDF tab and select the function name e g multivap libudf from the Heat Mass Transfer drop down list in the User Defined Functions group box Click OK See Section 2 5 6 DEFINE_DP
642. unction DEFINE Macro Dialog Box Activated In NO formation rates for DEFINE NOX RATE NOx Model Thermal NO Prompt NOx Fuel NO and N20 Pathways and upper limit for temperature PDF particle surface reaction rate Prandtl numbers species mass fraction velocity at a boundary pressure at a boundary temperature at a boundary mass flux at a boundary target mass flow rate for pressure outlet turbulence kinetic energy turbulence dissipation rate specific dissipation rate porosity viscous resistance inertial resistance porous resistance direction vector user defined scalar boundary value internal emissivity DEFINE PR_RATE DEFINE_PRANDTL DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE_PROFILE User Defined Function Hooks Viscous Model boundary condition e g Velocity Inlet boundary condition boundary condition boundary condition boundary condition Pressure Outlet boundary condition e g Velocity Inlet boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition boundary condition Release 12 0 ANSYS Inc January 26 2009 2 27 DEFINE Macros Table 2 3 3 Quick Reference Guide for Model Specific DEFINE Functi
643. ure is typically determined by P_T p Tracked_Particle p Tracked Particle p Tracked_Particle Material m p Tracked_Particle Material m p Tracked_Particle p material pointer boiling temperature char fraction diffusion coefficient to be used the gaseous boundary layer around particle emissivity for the radiation model evaporation temperature heat of pyrolysis heat of reaction latent heat specific heat of material used for liquid associated with particle dynamic viscosity of droplets scattering factor for radiation model specific heat at temperature t swelling coefficient for devolatilization surface tension of droplets vapor pressure of liquid part of particle vaporization temperature used to switch to vaporization law volatile fraction Release 12 0 ANSYS Inc January 26 2009 3 39 Additional Macros for Writing UDFs NO Macros The following macros can be used in NO model UDFs in the calculation of pollutant rates These macros are defined in the header file sg_nox h which is included in udf h They can be used to return real NO variables in SI units and are available in both the pressure based and the density based solver See Section 2 3 12 DEFINE_NOX_RATE for examples of DEFINE_NOX_RATE UDFs that utilize these macros Table 3 2 32 Macros for NO UDFs Defined in sg nox h Macro Returns POLLUT_EQN Pollut_Par index of pollutant equation being
644. ure that contains data related to the particle being tracked int num_p Not Used int n_spec Number of volumetric species double dt Time step double pres Pointer to pressure double temp Pointer to temperature double yk Pointer to array of initial species mass fractions Function returns void There are nine arguments to DEFINE_CHEM STEP name c p num p n spe dt pres temp and yk You supply name the name of the UDF c p n_spe dt pres temp and yk are variables that are passed by the ANSYS FLUENT solver to your UDF num_p is not used by the function and can be ignored The output of the function is the array of mass fractions yk after the integration step The initial mass fractions in array yk are overwritten Release 12 0 ANSYS Inc January 26 2009 2 31 DEFINE Macros Example The following UDF named user_chem_step assumes that the net volumetric reaction rate is the expression dY on i Nes 2 3 2 where Nspe is the number of species An analytic solution exists for the integral of this ODE as YA YP 1 Nape exp At 1 Nspe 2 3 3 paaa o kk k kkk kkk kkk kkk kk kk kkk k kk k Example UDF that demonstrates DEFINE_CHEM_STEP EEEE o k kkk kk kkk 4 4 24 kk include udf h DEFINE_CHEM_STEP user_chem_step cell thread particle nump nspe dt pres temp yk int i double c 1 double nspe double decay exp dt for i 0 i lt n_spe i yk i ykLli c decay c
645. urface Reaction Rate Function drop down list in the User Defined Function Hooks dialog box and click OK See Section 2 3 22 DEFINE_SR_RATE for details about DEFINE_SR_RATE functions 6 48 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 23 Hooking DEFINE_TRANS UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_TRANS UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT To hook the UDF select Transition SST from the Model list in the Viscous Model dialog box Figure 6 2 32 Were eee Edit Viscous Model Model Model Constants O Inviscid Alpha _inf O Laminar 1 Spalart Allmaras 1 eqn O k epsilon 2 eqn Alpha_inf Ok omega 2 eqn fo Sa Transition k kl omega 3 eqn i Transition SST 4 eqn Beta inf O Reynolds Stress 7 eqn i Detached Eddy Simulation O Large Eddy Simulation LES 0 09 al Options 0 31 C viscous Heating User Defined Transition Correlations F length user _Flength libudf Re_thetac user_Re_thetac libudf Re_thetat fuser _Re_thetat libud Figure 6 2 32 The Viscous Model Dialog Box Next select the function name e g user_Flength libudf from a drop down list in the User Defined Transition Correlatio
646. ut is prevented from being used outside the file even if is declared as external Functions can also be declared as static A static function is visible only to the source file in which it is defined static variables and functions can be declared only in compiled UDF source files Example Static Global Variable mysource c include udf h static real abs_coeff 1 0 static global variable used by both functions in this source file but is not visible to the outside DEFINE_SOURCE energy_source c t dS eqn real source local variable int P1 local variable value is not preserved when function returns dS eqn 16 abs_coeff SIGMA_SBC pow C_T c t 3 source abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 return source J A 6 Release 12 0 ANSYS Inc January 26 2009 A 6 User Defined Data Types DEFINE_SOURCE pi_source c t dS eqn real source int P1 dS eqn abs_coeff source abs_coeff 4 SIGMA_SBC pow C_T c t 4 C_UDSI c t P1 return source A 6 User Defined Data Types C also allows you to create user defined data types using structures and typedef For information about structures in C see 6 An example of a structured list definition is shown below i typedef can only be used for compiled UDFs Example typedef struct list int a real b int c mylist mylist is type structure list mylist x
647. ut DEFINE DPM SPRAY_COLLIDE functions 6 4 13 Hooking DEFINE _DPM_SWITCH UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DPM_SWITCH UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the Custom Laws dialog box Figure 6 4 14 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first create a particle injection in the Injections dialog box Define Injections Click Create in the Injections dialog box to open the Set Injection Properties dialog box so that you can set up the injection properties Enable the Custom option in the Laws group box in the Set Injection Properties dialog box in order to open the Custom Laws dialog box Figure 6 4 14 Custom Laws Inert Heating First Law Inactive Second Law Inactive Third Law Inactive Fourth Law Inactive Fifth Law Inactive Sixth Law Inactive Seventh Law Inactive Inactive Eighth Law v Ninth Law Inactive Tenth Law dpm_switch libudf v Switching Figure 6 4 14 The Custom Laws Dialog Box In the Custom Laws dialog box select the function name e g dpm switch libudf from the Switching drop down list and click OK 6 78 Release 12 0 ANSYS Inc January 26 2009 6 4 Hooking Discrete Phase Model DPM UDFs
648. variable arguments to sub_domain_loop are subdomain mixture_domain and phase_domain_index subdomain is a pointer to the phase level domain and mixture_domain is a pointer to the mixture level domain The mixture_domain is au tomatically passed to your UDF by the ANSYS FLUENT solver when you use a DEFINE macro that contains a domain variable argument e g DEFINE ADJUST and your UDF is hooked to the mixture If mixture_domain is not explicitly passed to your UDF you will need to use another utility macro to retrieve it e g Get_Domain 1 before calling sub_domain_loop see Section 3 2 6 Domain Pointer Get_Domain phase_domain_index is an index of subdomain pointers phase_domain_index is 0 for the primary phase and is incremented by one for each secondary phase in the mixture Note that subdomain and phase_domain_index are set within the sub_domain_loop macro Example The following interpreted UDF patches an initial volume fraction for a particular phase in a solution It is executed once at the beginning of the solution process The function sets up a spherical volume centered at 0 5 0 5 0 5 with a radius of 0 25 A secondary phase volume fraction of 1 is then patched to the cells within the spherical volume while the volume fraction for the secondary phase in all other cells is set to 0 3 60 Release 12 0 ANSYS Inc January 26 2009 3 3 Looping Macros DOR OK 2K 2K FK 2K 2K A RA RAK 2K K FK 2k 2K 2 FK 2 2k K 2k 26 2k K 2
649. variable macros 3 36 dpm h file 3 36 DPM_BOILING_ TEMPERATURE 3 37 DPM_CHAR_FRACTION 3 37 DPM_DIFFUSION_COEFF 3 37 DPM_EMISSIVITY 3 37 DPM_EVAPORATION_TEMPERATURE 3 37 DPM_HEAT_OF_PYROLYSIS 3 37 DPM_HEAT_OF_REACTION 3 37 DPM_LATENT_HEAT 3 37 DPM_LIQUID_SPECIFIC_HEAT 3 37 DPM_MU 3 37 DPM_OUTPUT 2 190 DPM_SCATT_FACTOR 3 37 DPM_SPECIFIC_HEAT 3 37 DPM_SURFTEN 3 37 DPM_SWELLING_COEFF 3 37 DPM_VAPOR _PRESSURE 3 37 DPM_VAPOR_TEMP 3 37 Release 12 0 ANSYS Inc January 26 2009 DPM_VOLATILE FRACTION 3 37 drag law default 2 141 DT_CG 3 43 DT_OMEGA CG 3 43 DT_THETA 3 43 DT_THREAD 2 210 2 219 3 43 DT_VEL_CG 3 43 duct flow 8 25 DYNAMESH_CURRENT_TIME 3 43 dynamic loading 1 6 5 2 dynamic mesh DEFINE macros quick reference guide 2 208 dynamic mesh macros 3 43 dynamic mesh UDFs center of gravity motion 2 209 deforming zone geometry 2 216 mesh motion 2 218 swirl center 2 211 variable cell layering height 2 211 Dynamic Mesh Zones dialog box 6 81 6 84 6 85 6 87 6 88 edge 1 10 elbow duct 8 14 emission term 2 39 emissivity weighting factor 2 42 emissivity weighting factor UDFs 2 41 emulator 1 6 environment compilation 5 4 erosion rate UDFs 2 167 Error 3 80 error messages 4 5 errors compiling source files 5 26 hooking UDFs 6 95 interpreting source files 4 5 parallel 5 28 Eulerian model DEFINE macro usage C 5 laminar flow C 8 C 10 C 13 examples real gas model UDFs 8 4
650. vector macro 3 23 face centroid macro 3 22 face ID 1 11 face identifier 3 2 face looping macros examples of 2 72 general purpose 7 25 face normal gradient 3 25 face partition IDs parallel 7 28 face variables macros 3 22 setting 3 34 face_t data type 1 10 fclose function A 15 fclose 7 40 FILE 3 33 file inclusion A 17 file inclusion directive 1 2 file sharing on Windows machines in parallel 4 3 File XY Plot dialog box 8 23 Fill Face_Part_With_Different 7 28 Fill Face_Part_With_Same 7 28 fixed value boundary condition UDFs 2 226 flow variable macros 3 8 3 24 FLUENT see ANSYS FLUENT FLUENT Launcher UDF options 5 4 Fluid dialog box 6 33 6 43 8 27 fluid thread checking 3 81 FLUID THREAD P 2 6 2 9 2 168 2 197 3 81 8 38 flux UDFs 2 226 fopen function A 14 fopen 7 40 for loops A 11 Release 12 0 ANSYS Inc January 26 2009 Index FORTRAN A 18 fprintf function A 15 fprintf 2 23 3 33 fscanf function A 16 fscanf 2 23 functions A 7 A 13 reader 2 23 writer 2 23 general purpose UDFs hooking to ANSYS FLUENT 6 1 general solver DEFINE macros quick reference guide 2 2 generic_property 2 92 Get_Domain 1 11 2 9 2 20 3 31 3 60 global reduction macros 7 17 gradient vector macros 3 8 gray band coefficient UDFs 2 43 header files 1 5 udf h 4 2 5 3 heat flux function 8 45 heat flux UDFs 2 45 heterogeneous reaction rate UDF 2 144 hooking UDFs to ANSYS
651. ver See Section 3 5 Time Dependent Macros for details on CURRENT _TIME Release 12 0 ANSYS Inc January 26 2009 2 7 DEFINE Macros POR o o ooo kkk k kkk kkk kkk kk kkk kkk kkk kkk k kkk kk k UDF that changes the time step value for a time dependent solution EEEE I I ooo A A A 1K 1 21 2 o kkk kk kkk kk kkk include udf h DEFINE_DELTAT mydeltat d real time_step real flow_time CURRENT_TIME if flow_time lt 0 5 time_step 0 1 else time_step 0 2 return time_step Hooking an Adaptive Time Step UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE DELTAT is interpreted Chapter 4 In terpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g mydeltat will become visi ble and selectable in the Adaptive Time Step Settings dialog box in ANSYS FLUENT See Section 6 1 2 Hooking DEFINE_DELTAT UDFs for details 2 2 3 DEFINE_EXECUTE_AT_END Description DEFINE_EXECUTE_AT_END is a general purpose macro that is executed at the end of an iteration in a steady state run or at the end of a time step in a transient run You can use DEFINE_EXECUTE_AT_END when you want to calculate flow quantities at these particular times Note that you do not have to specify whether your execute at end UDF gets executed at the end of a time step or the end of an iteration This is done automatically when you select the steady or unstead
652. w P UFree 2 Tw The friction factor is estimated from the Blasius equation 1 4 Ufree 0 045 PK kkk ak k k ak ak akak ak 2k kk 3k 2k K FK 2k 2K K FK 2K 2K K 2K 2K 2K FK 2K 2K K FK 2K 2K K FK 2K 2K FK 2K 2K K FK 2K 2K K 2K 2K K FK FK 2K K FK FK 2K K 2k 26 2k K 2k 2k 2 2k 2 2k Concatenated UDFs for fully developed turbulent inlet profiles EEEE ooo ooo kkk kk kkk kkk kkk include udf h define YMIN 0 0 constants define YMAX 0 4064 define UMEAN 1 0 define B 1 7 define DELOVRH 0 5 define VISC 1 7894e 05 define CMU 0 09 define VKC 0 41 profile for x velocity DEFINE_PROFILE x_velocity t i real y del h x ND_ND ufree variable declarations face_t f h YMAX YMIN del DELOVRH h ufree UMEAN B 1 begin_f_loop f t 2 76 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros end_ F_CENTROID x f t y xi if y lt del F_PROFILE f t i else F_PROFILE f t i ufree pow h y del B ufreexpow y del B f_loop f t profile for kinetic energy DEFINE_PROFILE k_profile t i real y del h ufree x ND_ND real ff utau knw kinf face_t f h del YMAX YMIN DELOVRH h ufree UMEAN B 1 ff 0 045 pow ufree del VISC 0 25 utau sqrt ff pow ufree 2 2 0 knw pow utau 2 sqrt CMU kinf 0 002 pow ufree 2 begin_f_loop f t
653. w Variable Macro Phase Specified On Boundary Conditions Inlet Outlet volume fraction species mass fractions mass flux velocity magnitude temperature pressure DEFINE_PROFILE DEF INE_PROFILE DEF INE_PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE PROFILE secondary phase s phase dependent primary and secondary phases s primary and secondary phases s primary and secondary phases s mixture Release 12 0 ANSYS Inc January 26 2009 C 4 Eulerian Model Mixture Turbulence Flow Table C 4 2 DEFINE Macro Usage for the Eulerian Model Mixture Turbu lence Flow Variable Macro Phase Specified On Boundary Conditions Inlet Outlet continued user defined scalar boundary value discrete phase boundary condition DEFINE PROFILE DEFINE PROFILE mixture mixture Fluid mass source momentum source energy source turbulence dissipation rate source turbulence kinetic energy source user defined scalar source user defined scalar turbulence kinetic energy turbulence dissipation rate velocity temperature porosity user defined scalar viscous resistance inertial resistance DEFINE SOURCE DEFINE_SOURCE DEFINE SOURCE DEFINE SOURCE DEFINE_SOURCE DEFINE_SOURCE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE DEFINE PROFILE DEFINE PROFILE DEFINE_PROFILE DEFINE_PROFILE primary and secondary phase s primary and secondary p
654. w Variables Defined in mem h Macro Argument Types Returns F_P f t face t f Thread t pressure F_FLUX f t face_t f Thread t mass flow rate through a face F_FLUX can be used to return the real scalar mass flow rate through a given face f in a face thread t The sign of F_FLUX that is computed by the ANSYS FLUENT solver is positive if the flow direction is the same as the face area normal direction as determined by F_AREA see Section 3 2 4 Face Area Vector F_AREA and is negative if the flow 3 24 Release 12 0 ANSYS Inc January 26 2009 3 2 Data Access Macros direction and the face area normal directions are opposite In other words the flux is positive if the flow is out of the domain and is negative if the flow is in to the domain Note that the sign of the flux that is computed by the solver is opposite to that which is reported in the ANSYS FLUENT GUI e g the Flux Reports dialog box 3 2 5 Connectivity Macros ANSYS FLUENT provides macros that allow the vectors connecting cell centroids and the vectors connecting cell and face centroids to be readily defined These macros return information that is helpful in evaluating face values of scalars which are generally not stored as well as the diffusive flux of scalars across cell boundaries The geometry and gradients involved with these macros are summarized in Figure 3 2 2 To better understand the parameters that are returned by these macro
655. where the particle is located in the given thread Thread t Pointer to the thread where the particle is located Tracked_Particle p Pointer to the Tracked_Particle data structure which contains data related to the particle being tracked Function returns real 2 1 86 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros There are four arguments to DEFINE_DPM_PROPERTY name c t and p DEFINE_DPM_PROPERTY has the same arguments as the DEFINE_PROPERTY function de scribed in Section 2 3 16 DEFINE PROPERTY UDFs with the addition of the pointer to the Tracked Particle p You supply name the name of the UDF c t and p are vari ables that are passed by the ANSYS FLUENT solver to your UDF Your UDF will need to compute the real value of the discrete phase property and return it to the solver Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example In the following example two discrete phase material property UDFs named coal_emissivity and coal_scattering respectively are concatenated into a single C source file These UDFs must be executed as compiled UDFs in ANSYS FLUENT kkk k k CCK K 2k 2k AR FK 2K k K 2K K K K 2K 2K FK FK 2K 2K 2K 2K 2K K K A FK 2K aK 2K 2K aK 2K 2K 2k K 2k FK 2K 2K kk 2 2k 2K 2K 2k K K K 2k FK FK UDF that specifies discrete phase materials BER
656. will be PDF integrated Any contribution from char must be included within a switch statement of the form Pollut_Par gt pollut_io_pdf OUT_PDF Arguments char sox_func_name UDF name cell_t c Cell index Thread t Pointer to cell thread on which the SOx rate is to be applied Pollut_Cell Pollut Pointer to Pollut structure Pollut_Parameter Pollut_Par Pointer to Pollut_Par structure SOx_Parameter SOx Pointer to S0x structure FO RR RK a 32k 2 2 2k 2k 3k 2k 2k a 2k 2k 2 ok 2k 2k 2 ok 2k 2k ak ok ak include udf h static void so2_so3_rate cell_t c Thread t Pollut_Cell Pollut Pollut_Parameter Pollut_Par SOx_Parameter SOx 2 1 08 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros DEFINE_SOX_RATE user_sox c t Pollut Pollut_Par SOx POLLUT_FRATE Pollut POLLUT_RRATE Pollut 0 0 0 0 switch Pollut_Par gt pollut_io_pdf case IN_PDF Included source terms other than those from char if SOx gt user_replace This rate replaces the default ANSYS FLUENT rate so2_so3_rate c t Pollut Pollut_Par SOx else This rate is added to the default ANSYS FLUENT rate so2_so3_rate c t Pollut Pollut_Par SOx break case OUT_PDF Char Contributions must be included here break default Not used break static void so2_so3_rate cell_t c Thread t Pollut_Cell Pollut Pollut_P
657. will be executed only once return UDM_checked because check_for_UDM checks for UDM_checked first void reset_UDM_s void Thread t cell_t c face_t fj int i if check_for_UDM Don t do it if memory is not available Release 12 0 ANSYS Inc January 26 2009 2 1 69 DEFINE Macros return Message Resetting User Defined Memory n thread_loop_f t domain if NNULLP THREAD_STORAGE t SV_UDM_I begin_f_loop f t for i 0 i lt NUM_OF_USED_UDM i F_UDMI f t i 0 F end_f_loop f t Message Skipping FACE thread no d n THREAD_ID t J thread_loop_c t domain if NNULLP THREAD_STORAGE t SV_UDM_I begin_c_loop c t for i 0 i lt NUM_OF_USED_UDM i C_UDMI c t i 0 end_c_loop c t Message Skipping CELL thread no d n THREAD_ID t Skipping Cell Threads can happen if the user uses reset_UDM prior to initializing Message Done n DEFINE_DPM_SCALAR_UPDATE dpm_scalup c t if_init p if if_init P_USER_REAL p 0 0 Simple initialization Used later for 2 1 70 Release 12 0 ANSYS Inc January 26 2009 2 5 Discrete Phase Model DPM DEFINE Macros stopping trajectory calculation DEFINE_DPM_EROSION dpm_accr p t f normal alpha Vmag Mdot real A ND_ND area int num_in_data Thread t0 cell_t cO real radi_pos 2 radius imp_vel 2 vel_ortho
658. will be stored in S Pointer p can be used as an argument to the macros defined in Sec tion 3 2 7 DPM Macros to obtain information about particle properties e g injection properties Example See Section 2 5 13 Example for an example of DEFINE_DPM_SOURCE usage Release 12 0 ANSYS Inc January 26 2009 2 1 93 DEFINE Macros Hooking a DPM Source Term UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_DPM_SOURCE is interpreted Chap ter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument will become visible in the Discrete Phase Model dialog box in ANSYS FLUENT See Section 6 4 11 Hooking DEFINE_DPM_SOURCE UDF s for details on how to hook your DEFINE_DPM_SOURCE UDF to ANSYS FLUENT 2 5 12 DEFINE_DPM_SPRAY_COLLIDE Description You can use DEFINE_DPM_SPRAY_COLLIDE to side step the default ANSYS FLUENT spray collision algorithm When droplets collide they may bounce in which case their velocity changes or they may coalesce in which case their velocity is changed as well as their diameter and number in the DPM parcel A spray collide UDF is called during droplet tracking after every droplet time step and requires that Droplet Collision is enabled in the Discrete Phase Model dialog box Usage DEFINE_DPM_SPRAY_COLLIDE name tp p Argument Type Description symbol name UDF name Tracked Particle tp Pointer to
659. will occur return ruser 2 pow MAX 0 ruser 0 rate ruser 1 order rate DEFINE_PR_RATE user_rate c t r mw pp p sf dif_i cat_i rr if if strcmp r gt name reaction 2 2 62 cxboolean ifail FALSE real ash_mass P_INIT_MASS p 1 DPM_CHAR_FRACTION p DPM_VOLATILE_FRACTION p real one_minus_conv MAX O P_MASS p ash_mass P_INIT_MASS p DPM_CHAR_FRACTION p real ruser 3 int iuser 1 cxboolean buser 1 char cuser 30 real ratemin ratemax root ruser 0 ppldif_i ruser 1 MAX 1 E 15 cl pow 0 5 P_T p C_T c t 0 75 P_DIAM p ruser 2 A1 exp E1 UNIVERSAL_GAS_CONSTANT P_T p strcpy cuser reaction 2 ratemin 0 ratemax ruser 1 pp dif_i arguments for auxiliary function zbrent_pr_rate root zbrent_pr_rate reaction_rate ruser iuser buser cuser ratemin ratemax tolerance amp ifail if ifail root MAX 1 E 15 ruser 1 Release 12 0 ANSYS Inc January 26 2009 2 3 Model Specific DEFINE Macros rr root P_DIAM p P_DIAM p M_PI sf 0 one_minus_conv Message Fail status d n ifail Message Reaction rate for reaction s g n cuser rr In this example a real function named reaction_rate is defined at the top of the UDF The arguments of reaction_rate are real rate and the pointer arrays real ruser integer iuser cxboolean buser and char cuser which must be declared and defined in the
660. wing UDF named tm_pout2 adjusts the mass flow rate from 1 00kg s to 1 35kg s when the physical time step is greater than 0 2 seconds After it has been interpreted or compiled you can activate this UDF in the Pressure Outlet boundary condition dialog box in ANSYS FLUENT by selecting the Specify target mass flow rate option and then choosing the UDF name from the corresponding drop down list Note that the mass flow rate profile is a function of time and only one constant value should be applied to all zone faces at a given time UDF for setting target mass flow rate in pressure outlet at t lt 0 2 sec the target mass flow rate set to 1 00 kg s when t gt 0 2 sec the target mass flow rate will change to 1 35 kg s include udf h DEFINE_PROFILE tm_pout2 t nv face_t f real flow_time RP_Get_Real flow time if flow_time lt 0 2 printf Time f sec n flow_time printf Targeted mass flow rate set at 1 0 kg s n begin_f_loop f t F_PROFILE f t nv 1 0 end_f_loop f t else printf Time f sec n flow_time printf Targeted mass flow rate set at 1 35 kg s n begin_f_loop f t Release 12 0 ANSYS Inc January 26 2009 2 85 DEFINE Macros F_PROFILE f t nv 1 35 end_f_loop f t Example 9 Mass Flow Rate UDF for the Mass Flow Inlet This UDF is used to provide a time varying specification of the mass flow rate This boundary condition can
661. x Click OK to close the Phase Interaction dialog box See Section 2 4 4 DEFINE_MASS_TRANSFER for details about writing DEFINE_MASS_TRANSFER functions 6 3 5 Hooking DEFINE_VECTOR_EXCHANGE_PROPERTY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE VECTOR EXCHANGE RATE UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Functions dialog box Figure 6 3 9 in ANSYS FLUENT To hook the UDF to ANSYS FLUENT first select Mixture from the Model list of the Multiphase Model dialog box and make sure that the Slip Velocity option is enabled Teta Dees Edit Next open the Phase Interaction dialog box Figure 6 3 8 Release 12 0 ANSYS Inc January 26 2009 6 61 Hooking UDFs to ANSYS FLUENT 4 MESSA Interaction Phase Interaction Drag Lift Collisions Slip Heat Mass Reactions Surface Tension Slip velocity m s phase 2 phase 1 user defined custom_slip libudf cone Cee Figure 6 3 8 The Phase Interaction Dialog Box Click the Slip tab in the Phase Interaction dialog box and select user defined from the drop down list for the Slip Velocity This will open the User Defined Functions dialog box User Defined Fu custom slip libudf Figure 6 3 9 The User Defined Functions Dialog Box Fi
662. y Release 12 0 ANSYS Inc January 26 2009 6 17 Hooking UDFs to ANSYS FLUENT Create Edit Materials fx a E Mixture et cori cone Figure 6 2 5 The Create Edit Materials Dialog Box 6 1 8 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs 6 2 4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs After you have interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Com piling UDFs your DEFINE_DOM_DIFFUSE_REFLECTIVITY UDF the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User Defined Function Hooks dialog box Figure 6 2 6 in ANSYS FLUENT The discrete ordinates DO radiation model must be enabled from the Radiation Model dialog box To hook the UDF to ANSYS FLUENT open the User Defined Function Hooks dialog box Figure 6 2 6 Define User Defined Function Hooks User Defined Function Hooks Initialization Adjust Execute at End Read Case Write Case Read Data Write Data Execute at Exit Wall Heat Flux Chemistry Step Cavitation Mass Rate DO Source DO Diffuse Reflectivity user_dom_diff_refl slibudlf DO Specular Reflectivity DO Emissivity Weighting Factor Figure 6 2 6 The User Defined Function Hooks Dialog Box Select the function name e g user_ dom diff_refl libudf in the
663. y double precision should be used for all local variables Release 12 0 ANSYS Inc January 26 2009 2 51 DEFINE Macros Hooking a Net Reaction Rate UDF to ANSYS FLUENT After the UDF that you have defined using DEFINE_NET_REACTION_RATE is interpreted Chapter 4 Interpreting UDFs or compiled Chapter 5 Compiling UDFs the name of the argument that you supplied as the first DEFINE macro argument e g net_rxn will become visible and selectable in the User Defined Function Hooks dialog box in ANSYS FLUENT See Section 6 2 11 Hooking DEFINE_NET_REACTION_RATE UDFs for details 2 3 12 DEFINE NOX RATE Description You can use the DEFINE NOX RATE to specify a custom NO rate for thermal NOx prompt NOx fuel NOx and N20 intermediate pathways that can either replace the internally calculated NO rate in the source term equation or be added to the ANSYS FLUENT rate Example 1 demonstrates this use of DEFINE_NOX_RATE By default the Add to FLUENT Rate option is enabled UDF Rate group box in each of the tabs under Formation Model Parameters so that user defined rates are added to the ANSYS FLUENT calculated rates You can change this default by selecting Replace FLUENT Rate so that the ANSYS FLUENT calculated rate for that NO pathway will not be used and it will instead be replaced by the NO rate you have defined in your UDF i Note that a single UDF is used to define the different rates for the four NO pathways thermal NOx pr
664. y Z x y z are type structure list A 7 Casting You can convert from one data type to another by casting A cast is denoted by type where the type is int float etc as shown in the following example int x 1 real y 3 14159 int z x int y z 4 A 8 Functions Functions perform tasks Tasks may be useful to other functions defined within the same source code file or they may be used by a function external to the source file A function has a name that you supply and a list of zero or more arguments that are passed to it Note that your function name cannot contain a number in the first couple of characters A function has a body enclosed within curly braces that contains instructions for carrying Release 12 0 ANSYS Inc January 26 2009 A 7 C Programming Basics out the task A function may return a value of a particular type C functions pass data by value Functions either return a value of a particular data type e g real or do not return any value if they are of type void To determine the return data type for the DEFINE macro you will use to define your UDF look at the macro s corresponding define statement in the udf h file or see Appendix B for a listing C functions cannot alter their arguments They can however alter the variables that their arguments point to A 9 Arrays Arrays of variables can be defined using the notation name size where name is the variable name and size is
665. y time method in your ANSYS FLUENT model Release 12 0 ANSYS Inc January 26 2009 2 2 General Purpose DEF INE Macros Usage DEFINE _EXECUTE_AT_END name Argument Type Description symbol name UDF name Function returns void There is only one argument to DEFINE_EXECUTE_AT_END name You supply name the name of the UDF Unlike DEFINE_ADJUST DEFINE_EXECUTE_AT_END is not passed a do main pointer Therefore if your function requires access to a domain pointer then you will need to use the utility Get_Domain ID to explicitly obtain it see Section 3 2 6 Do main Pointer Get_Domain and the example below If your UDF requires access to a phase domain pointer in a multiphase solution then it will need to pass the appropriate phase ID to Get_Domain in order to obtain it Example The following UDF named execute_at_end integrates the turbulent dissipation over the entire domain using DEFINE_EXECUTE_AT_END and displays it in the console at the end of the current iteration or time step It can be executed as an interpreted or compiled UDF in ANSYS FLUENT PRR o oo o kk kkk kk kkk CA A A A A kk KK KOK UDF for integrating turbulent dissipation and displaying it in the console at the end of the current iteration or time step BER AAR AAAI RI I I I KK AK AK AE A A A A A KK KKK A A A A 2A kK KK kkk kk kk include udf h DEFINE_EXECUTE_AT_END execute_at_end Domain d Thread t Integrate dissipation rea
666. you supplied in the DEFINE macro argument will become visible and selectable in the NOx Rate drop down list in the Formation tab of the NOx Model dialog box Figure 6 2 14 gt VAR gt gt N ya Edit NOx Model Models Formation Model Parameters Formation Reduction Turbulence Interaction Mode Thermal Prompt Fuel N20 Path Pathways 0 Model partial equilibrium V Thermal NOx CIEN e Prompt NOx partial equilibrium Fuel NOx UDF Rate N2O Intermediate Replace FLUENT Rate Add to FLUENT Rate Fuel Streams Number of Fuel Streams 5 Ina jte jv Fuel Species B o2 co2 User Defined Functions NOx Rate apama anne v Figure 6 2 14 The NOx Model Dialog Box Recall that a single UDF is used to define custom rates for the thermal NOx prompt NO fuel NO and N2O NO pathways By default the custom NO rate of your UDF is added to the rate calculated internally by ANSYS FLUENT for each pathway The UDF rate will be added to the forward rate if it is assigned to the POLLUT_FRATE macro or the reverse rate if it is assigned to the POLLUT_RRATE macro If you would rather entirely 6 28 Release 12 0 ANSYS Inc January 26 2009 6 2 Hooking Model Specific UDFs replace the internally calculated NO rate with your custom rate click the desired NO pathway tab Thermal Prompt Fuel or N2O Path under Formation Model Parameters select Replace FLUENT
667. your DEFINE_GEOM UDF to ANSYS FLUENT Release 12 0 ANSYS Inc January 26 2009 2 217 DEFINE Macros 2 6 4 DEFINE_GRID_MOTION Description By default ANSYS FLUENT updates the node positions on a dynamic zone by applying the solid body motion equation This implies that there is no relative motion between the nodes on the dynamic zone However if you need to control the motion of each node independently then you can use DEFINE_GRID_MOTION UDF A mesh motion UDF can for example update the position of each node based on the deflection due to fluid structure interaction Note that UDFs that are defined using DEFINE GRID MOTION can be executed only as compiled UDFs Usage DEFINE_GRID_MOTION name d dt time dtime Argument Type Description symbol name UDF name Domain d Pointer to domain Dynamic_Thread dt Pointer to structure that stores the dynamic mesh attributes that you have specified or that are calculated by ANSYS FLUENT real time Current time real dtime Time step Function returns void There are five arguments to DEFINE_GRID_MOTION name d dt time and dtime You supply name the name of the UDF d dt time and dtime are variables that are passed by the ANSYS FLUENT solver to your UDF 2 218 Release 12 0 ANSYS Inc January 26 2009 2 6 Dynamic Mesh DEFINE Macros Example Consider the following example where you want to specify the deflection on a cantilever beam based on the x po

ANSYS FLUENT 12.0 UDF Manual

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