Introduction to PORFLO and user instructions 2010
Contents
1. PORFLO solves the Navier Stokes equations for liquid and gas phases in three dimensions In contrast to many other CFD codes PORFLO utilizes porous medium approach instead of body fitting the mesh to the modelled geometry In this approach the exact locations of the walls of solid structures are not known VIT RESEARCH REPORT VTT R 00446 11 5 32 The advantage of the approach is that it allows the modelling of complex systems such as tube bundles without the heavy computational effort that would be necessary with a detailed model of the flow channels The inherent drawback of this approximation is that the exact flow field within the pores or channels of the geometry is not known and the physical phenomena including heat transfer and turbulence are averaged over a selected volume which contains both fluid and solid phases This report describes the code development status in 2010 and gives general user instructions for setting up and running PORFLO simulations in Linux environment Instructions for post processing are also presented and examples of using the multi purpose StarNode visualization tool developed by VTT are given 2 PORFLO basics PORFLO solves the six conservation equations of mass momentum and energy for the liquid and gas phases Also a 5 equation model in which the liquid and gas phases are separated by the drift flux model is available but this has been replaced by the six equation model in recent applications The con2. The geometry and grid information is handled on the level of YIT RESEARCH REPORT VTT R 00446 11 10 32 the source code in contrast to many commercial codes such as GAMBIT so modifications to be made into the grid have to be programmed into the Geometry F90 module which contains sub routines for each of the five applications The physical boundaries of the modelled geometry are smoothed on the Cartesian grid in such a way that in the grid cell in which the physical boundary is located porosity of the cell is weighted according to the fractions of different structures in the cell in question Using this method even highly complex geometries can be described with relative ease but with the cost of losing information of the exact geometry in the flow solution Example grids are presented in Fig 2 and Fig 3 The vertical cross sections in the centre of the 3D grids for the conical particle bed that of the COOLOCE facility and for the somewhat simpler cylindrical particle bed are illustrated in Fig 2 and Fig 3 respectively The cell size in the example grids is 3 cm 0 Fig 2 Cartesian 21x21x28 grid for the COOLOCE particle bed including a large pool volume The color scale indicates porosity Porosity in the conical region is approximately 36 VIT RESEARCH REPORT VTT R 00446 11 3 2 11 32 Fig 3 Cartesian 21x21x28 grid for a cylindrial particle bed vertical left and horizontal right cross sections T
3. 197 p ISBN 0 89116 552 3 RESEARCH REPORT VTT R 00446 11 a ALA 25 32 Qt Cross platform application and UI framework http qt nokia com July 20 2010 Takasuo E Hovi V Ilvonen M 2011 PORFLO modelling of the coolability of porous particle beds VTT Research Report VTT R 09376 10 Espoo 2011 41 p Takasuo E Kinnunen T Pankakoski P H Holmstr m S 2010 Description of the COOLOCE test facility Conical particle bed VTT Research Report VTT R 08956 10 Espoo 2010 18 p VIT RESEARCH REPORT VTT R 00446 11 Al APPENDIX A List of PORFLO updates for the porous particle bed application in 2010 1 The particle bed geometry routine for the generation of the COOLOCE test facility model has been implemented 3 2010 2 The heat transfer solution routine has been modified so that the heating power may be given as an input value instead of surface temperatures 4 2010 3 A selection of heat transfer models for the particle bed application has been included 4 2010 The models utilized in the MEWA WABE code B rger et al 2006 were used as a starting point for the model implementation 4 A selection of particle bed friction models has been included 4 2010 The models are based on well known approaches for modelling porous media 5 The particle bed geometry routine has been modified for investigations of cylindrical geometries 6 2010 6 Possibilities for writing time dependent output mo
4. Step 5 Calculate the mass flow rates explicitly Integrate liquid amp vapour masses Calculate structure heat transfer Calculate interfacial heat transfer Solve enthalpy equations for liquid amp vapour Calculate mixture densities and void fractions from liquid amp vapour masses Converged Yes No New time step Fig 1 The solution procedure of PORFLO VIT RESEARCH REPORT VTT R 00446 11 8 32 3 Setting up simulations PORFLO simulations are set up by editing the input file porflo dat and modifying the application specific parts of the source code The code does not include a general form user interface Thus it is almost always necessary to edit the source code to specify the simulation parameters Naturally source editing has to be done also if the user wishes to apply new models and correlations It should be noticed that to some extent programming is also necessary when using commercial codes such as FLUENT in which User Defined Functions UDFs are used to include specific models which are not available as default Even though easy readability and comprehensive comments are emphasized source editing is not always a straightforward process and the user should be familiar with the basics of programming in Fortran and the architecture of PORFLO On the other hand user programming offers a lot of possibilities for modifying the code for solving different kinds of flow problems The source code con
5. first four options are aimed for the particle bed application and the last one for the horizontal steam generator application It should be noticed that the present code version does not include models verified for open pools The flows in open pools are approximated using the porous medium and tube bundle friction models 1 5 or alternatively the Fictional loss coefficient in the General input section may be used VIT RESEARCH REPORT VTT R 00446 11 14 32 Next the friction model between the solid matrix and the fluid phases is given for the porous section of the geometry The first four options 1 4 are commonly known models that are verified and validated for particle bed simulations and the last one 5 for the horizontal steam generator with flow across tube bundles For information on the selection of a suitable particle bed friction model see Takasuo et al 2010 The last two options give the friction between the gas and liquid phases This is separately given for the particle bed region and the open pool region The interfacial friction may also be turned off by selecting zero For the particle bed application the Tung and Dhir model is the recommended selection FAHAHAHA HHH DISCRETIZATION 43 Index for selecting the discretization scheme 1 Downwind scheme 2 Central difference scheme 3 Upwind scheme 4 Second order upwind scheme 5 FROMM 6 SUPERBEE 7 MNMOD 8 OSHER 9 MU
6. mass inside the particle bed 66 4658116372507 Vapor mass inside the particle bed 5 999543779945474E 003 Liquid massflow out of the particle bed 1 547510472827853E 002 Vapor massflow out of the particle bed 1 547624379678370E 002 INPUT VALUES time_s 2481 16000 dtime_s 0 01000 time_min 2010 00000 time_max 2500 00000 Power KW 35 00000 glin 0 000E 00 p_system 0 100E 06 p_system_bar 0 100E 01 Possible breakdown dot2 4 589679784884888E 062 Possible breakdown dot2 2 279529682505454E 109 Possible breakdown dot2 6 255284805235861E 057 Possible breakdown dot2 7 661167708683980E 099 Possible breakdown dot2 4 590908788373912E 062 Possible breakdown dot2 2 266957398103207E 109 Possible breakdown dot2 6 255151368848210E 057 Possible breakdown dot2 7 662559230645362E 099 Possible breakdown dot2 4 589842714228127E 062 Possible breakdown dot2 2 279738633534677E 109 Possible breakdown dot2 6 255237963332649E 057 Possible breakdown dot2 7 662661631610286E 099 Possible breakdown dot2 4 590213923079704E 062 Possible breakdown dot2 2 273915384433118E 109 Possible breakdown dot2 6 255182751701605E 057 Possible breakdown dot2 7 661627775431119E 099 Possible breakdown dot2 4 590208071977607E 062 Possible breakdown dot2 2 274002521603293E 109 Possible breakdown dot2 6 255154050626475E 057 Possible breakdown dot2 7 661009617219395E 099 Possible breakdown dot2 4 591071760542527E 062 Possible breakdo
7. may be chosen to improve the convergence and calculation speed of certain cases The maximum number of temperature iterations 5 iterations in the example defines the maximum number of heat transfer temperature iterations within a loop in which all the heat transfer coefficients are calculated before the simultaneous solution of all the temperatures FAH AH SOLUTION METHODS 43 HHHA AHHH Index for selecting the friction model for FREE FLOW open pool 1 Lipinski 2 Reed 3 Hu amp Theofanous 4 Tung amp Dhir 5 Isachenko for Horizontal SG 4 Index for selecting the friction model for FLOW THROUGH POROUS MATERIAL 1 Lipinski 2 Reed 3 Hu amp Theofanous 4 Tung amp Dhir 5 Isachenko for Horizontal SG 4 r ROE HE HE HEE Index for selecting the InterPhase Friction model for FREE FLOW open pool 0 No InterPhase Friction 1 Tung amp Dhir 2 Isachenko for Horizontal SG 1 Index for selecting the InterPhase Friction model for FLOW THROUGH POROUS MATERIAL 0 No InterPhase Friction 1 Tung amp Dhir 2 Isachenko for Horizontal SG 1 FERRE AEA initiaieitieititieiareiareiiar tiares aitinitinitit isitin initiaieitieitieitiareiareiaiei tiar aiartiar iiinis The selection of the physical friction models is given above First the friction model for the open pool with no porosity as the default is given indices 1 5 The
8. 00 00 1 d 2 25 0d 3 0 00 1 0d5 1510 00 1 d 2 30 0d 3 0 00 1 0d5 2000 00 1 d 2 30 0d 3 0 00 1 0d5 2010 00 1 d 2 35 0d 3 0 00 1 0d5 2500 ea 1 d 2 35 0d 3 0 00 1 0d5 1 0 1 d 1 35 0d 3 0 00 1 0d5 FER AEE tiaraa aiai aitiniini id In this section the time dependent input values are given These are time step width d_time heating power total power inlet boundary mass flow rate glin and system pressure p_system The values signed indicate that the possible change of the value is done as a liner increase from the previous value up to the time indicated on the same line indicates that the change is instantaneous For restart calculations it e be noticed that the time_max value has already been read at the time of the restart file save and the time dependent input for restart calculations should be started from a time value greater than the time_max that is set in the restart text file For restarting from a previous save the output text file should be named porflo0 txt 4 Running calculations After the simulation has been set up and the input file porflo dat generated the source code including the case specific modifications has to be compiled The code developers use Intel Fortran Compiler for Linux operating systems and Visual Studio for Windows Once compiled calculation is started by executing the output file generated by the compiler we recommend
9. 7 Animation file animation bin The mass flux monitor file contains the mass flow rates across horizontal cross sections of the modelled geometry The heat transfer monitor file contains the total heat fluxes of the different heat transfer mechanisms present in the modeled system example of which was plotted in Fig 5 For post processing purposes however it is more convenient to examine these variables through the porflo txt output file There are presently two options for post processing and flow field visualization that directly utilize the main output file 1 Matlab 2 StarNode YIT RESEARCH REPORT VTT R 00446 11 22 32 Matlab can be used for 2D plotting by simple script files PlotFromRestart m and ResidualPlot m However more comprehensive visualization options are provided by the StarNode visualization tool StarNode is based on the open source graphics rendering engine Ogre3D http www ogre3d org and the QT user interface toolkit http qt nokia com Presently StarNode is capable of rendering hundreds of thousands of nodes Ilvonen et al 2010 Various data sets can be visualized by the code and 2D cross sections created from the 3D data Vector data may also be plotted Examples of creating plots and animation can be found in Appendix B More information is found in the StarNode User s Manual Inkinen 2010 Examples of 2D and 3D graphs generated using StarNode are shown in Fig 7 The graphs re
10. D View PORFLO Object 1 000e 000 Show axes True Z Properties gx Name Nodes in x direction 2 Nodes in y direction 2 Nodes in z direction 2s Data set Alpha_g Ai T Unit 0 Frese nos secon rase False 4 Color scale Default x Automatic bounds _ False Use overall bounds True Y Minimum o 0000000E 00 S Maximum 1 0000000E 00__ OOB rendering clamp J 0 000e 000 Vunr RESEARCH REPORT VTT R 00446 11 AS 7 The Create cross section button provides the possibility to view cross sections of the nodal data in 3D A slice of the geometry is shown in the 3D View according to the selected axis in the Direction menu and the index of the grid cells in the Index menu In the example seen in the figure below we use index 11 to see the central plane of the geometry StarNode 0 4 2 File Edit Tools View Help DEO xXB Mode Explorer BB Model Y 3D View PORFLO Object PORFLO Object Nodes in x direction p Nodes in y direction Nodes in z direction Alpha_g Unit Direction Index Use optional index Optional index Automatic bounds False Use overall bounds True Minimum 0 0000000E 00 Maximum 1 0000000E 00 OOB rendering Clamp Show axes v K lt I DP 1 000e 000 0 000e 000 8 The Use data mask button provide
11. Model Master s Thesis Lappeenranta University of Technology 112 p Hovi V Ilvonen M 2010 PORFLO Simulations of Loviisa Horizontal Steam Generator VTT Research Report VTT R 01406 10 Espoo 34 p Hovi V Ilvonen M 2010 3D PORFLO simulations of Loviisa steam generator AER Symposium September 20 24 2010 Hanasaari Espoo Finland Hyytinen K 2001 Partikkelikeon ja ahdytyskokeiden analysointi Master s Thesis Tampere University of Technology 2001 67 p Ilvonen M Hovi V 2009 The porous medium model PORFLO for 3D two phase flow and its application to BWR fuel bundle simulations Eija Karita Puska Ed SAFIR2010 The Finnish Programme on Nuclear Power Plant Safety 2007 2010 Interim Report VTT Research Notes 2466 Helsinki 2009 ISBN 978 95 1 38 7266 3 Pp 131 141 Ilvonen M Hovi V Inkinen P 2010 PORFLO development applications and plans in 2008 2009 VTT Research Report VTT R 01414 10 Espoo 28 p Inkinen P 2010 StarNode v0 4 0 User s Manual Miettinen J Karppinen I 2003 A Porous Media Calculation Applications for the Isolation Condenser Heat Transfer and Circulation The 10 International Topical Meeting on Nuclear Reactor Thermal Hydraulics NURETH 10 Seoul Korea October 5 9 2003 OGRE Open Source 3D Graphics Engine http www ogre3d org July 20 2010 Patankar S V 1980 Numerical Heat Transfer and Fluid Flow New York Hemisphere Publishing Corporation
12. RESEARCH REPORT VTT R 00446 11 Introduction to PORFLO and user instructions 2010 Authors Eveliina Takasuo Ville Hovi Mikko Ilvonen Confidentiality Public Vunr RESEARCH REPORT VTT R 00446 11 1 32 Report s title Introduction to PORFLO and user instructions 2010 Customer contact person address Order reference SAFIR2010 National Research Programme on Nuclear Power 7 2007 SAF Plant Safety Project number Short name 41435 TRICOT_2010 43216 PORFLO koulutus Project name Tridimensional core transient analysis methods PORFLO koulutus ja sovellus partikkelikeon j hdytett v Y Author s Pages Eveliina Takasuo Ville Hovi Mikko Ilvonen 25 p 2 appendices Keywords Report identification code PORFLO code thermal hydraulics porous medium two phase VTT R 00446 11 flow user instructions Summary PORFLO is a 3D two phase flow simulation code which utilizes the porous medium approach in the modelling of complex geometries The code has been developed specifically for thermal hydraulic safety analysis of nuclear power plants The code has recently been under development at VTT for the following applications core debris coolability secondary side of steam generators flows across fuel bundles and the EPR reactor downcomer lower plenum and core In the future the aim is to connect PORFLO to the family of system codes and reactor core simulators particularly TRAB 3D SMABRE
13. SCL Discretization scheme for Velocities 3 Discretization scheme for Volume fractions 3 Discretization scheme for Temperatures 3 HHHHHHHHHHHHHHHHHHH UNDER RELAXATION FACTORSHHHHHHHHHHHHHHHHHHHHHHH Under Relaxation Factor for Pressure 0 7 Under Relaxation Factor for Velocities 0 5 Under Relaxation Factor for Volume fractions 1 0 Under Relaxation Factor for Temperatures 1 0 FEE AAR The discretization schemes and under relaxation factors are defined above The default option is first order upwind Often the values that produce the fastest convergence are case dependent and have to be selected by trial and error VIT RESEARCH REPORT VTT R 00446 11 15 32 FARAH AAA ITERATIVE LINEAR SOLUTION HHHHHHHHHHHHHHHHHHHHHHH Minimum Maximum number of number of Tolerance iters iters i 3 1000 1 0e 8 Velocities i 10 10000 1 0e 8 Pressure correction i 3 1000 1 0e 10 Volume fractions 3 1000 1 0e 10 Temperatures FER AEE eiar iitinitinitit isitin ieitiaieiaieitieitiareiareiaiei tiaraa tiai aitiniini id The minimum and maximum number of iterations and the convergence criterion for the solutions of velocity pressure correction volume fractions of the phases and temperature are given in this section Tolerance indicates the difference in the Euclidean norm of the residuals The default values are seen above FBR HAH MONITORS 4H Number of monitors 9 Variabl
14. andy in creating animations because now the color scale is not automatically adjusted between the different screens You can switch between 2D and 3D views by clicking the 3D View and Cross Section 1 View tabs on the top of the current view YIT RESEARCH REPORT VTT R 00446 11 A4 Creating a 3D Plot 1 Start the StarNode software 2 Inthe program menu select File Import Model and select the appropriate file in this case porflo txt Select the format of the data file PORFLO Restart File and click OK to read the data file 3 To access the options of the Properties window for the 3D Plot select left click PORFLO Object in the Model Explorer window on the left 4 The 3D View can be zoomed in and out by the mouse wheel and rotated by dragging the mouse while pressing the right mouse button Rotation can also be done by the arrow keys 5 Click the Data set button and select the variable to be plotted from the drop down menu Here we take the void fraction Alpha_g as the example variable 6 As in the 2D Plot example we select overall bounds for the color scale by clicking the Color scale selecting the Use overall bounds and giving 0 0 for the Minimum limit and 1 0 for the Maximum limit The axes may be turned on and off from the Show axes selection The resulting 3D view is shown in the figure below m StarNode 0 4 2 File Edit Tools View Help DEH XBOS KAP OPA at SpE ETS a om e Model amp Y 3
15. ation For the particle bed application the selection of the friction models is provided in the input file which is presented in the next section The calculation of heat transfer coefficients is found in the module HeatTransfer F90 The module calculates the heat transfer rates between the three different phases namely liquid solid and vapour and the phase interface boiling The possibility to solve heat conduction within solid materials has been included in the particle bed model and the fuel rod bundle model that was used in the BFBT benchmark The correlations for the different heat fluxes are clearly commented in the code and the user may modify or add his her own correlations into the module In addition appropriate boundary conditions have to be specified for the simulations The below options are pre set in the input file named porflo dat see the example in Section 3 2 1 Frictionless wall 2 Velocity inlet 3 Pressure outlet The inclusion of other boundary types is possible and will be done according to the requirements of future applications and user needs Grid generation The spatial discretization is based on 3D Cartesian staggered grids A sub routine that performs the creation of the grid for the problem geometry has to be included for each application This routine generates the three dimensional arrays for porosity power sources and other node specific data such as the areas used in heat transfer calculations
16. ation interval in seconds 1 0d 1 Beginning time for animation in seconds 0 0d 0 End time for animation in seconds 10000 0d 0 FERRE EAE AEE A A EE A A A eiai eiai aiaiai The specifications for saving the binary data for generating animations of the simulations are given in this section The selected variables 1 5 and the phase 0 2 are saved for all mesh points The interval of the animation screens and the beginning and end simulation times for the animation are given The default name of the animation file is animation bin JAH INITIAL VALUES 33 Beginning of the simulation s 0 0d 0 Length of time step s 1 0d 2 Total heating power W 1 0d 0 Liquid mass flow rate at inlet kg s 0 0d 0 System pressure Pa 1 0d 5 FEAR EEE EE AEE A This section presents the initial values and the width of the time step used in the simulation If a restart file is read this part of the input is skipped The heating VIT RESEARCH REPORT VTT R 00446 11 17 32 power is given as total power of all the heat generating structure of the geometry in watts FHA NEW INPUT VALUES FOR EACH TIME INTERVAL HHHH HHHH HHHH time_max dtime total_power glin p system s s Ww kg s Pa 10 000 1 d 2 15 0d 3 0 00 1 0d5 500 00 1 d 2 15 0d 3 0 00 1 0d5 510 00 1 d 2 20 0d 3 0 00 1 0d5 1000 00 1 d 2 20 0d 3 0 00 1 0d5 1010 00 1 d 2 25 0d 3 0 00 1 0d5 15
17. aulics system code SMABRE and eventually to the neutronics models TRAB 3D in nuclear reactor core analysis The possibility to parallelize the code has also been investigated but not yet put to practice in production runs Another specific application of PORFLO is the heat transfer and two phase flow in a core debris bed that generates decay heat a problem specific to severe accident analysis Predicting the dryout heat flux coolability in a porous debris bed was one of the first applications of the PORFLO predecessor PILEXP code Hyytinen 2001 The re introduction of this problem to be solved with the up to date PORFLO version was done within the SAFIR2010 HYBCIS2 project A new laboratory scale test facility COOLOCE Coolability of Cone using which the coolability of a heap like conical debris bed may be investigated was assembled in the project in 2010 Takasuo et al 2010 Traditionally the dryout behavior of porous particle beds consisting of core debris has been evaluated by 1D models or simple correlations However in realistic accident scenarios the particle bed may have a highly irregular structure or a heap like geometry In these cases the simplified approaches might not be adequate due to complex multi dimensional flow configurations allowed by the debris bed geometry Also multi dimensional flooding is present in the conical test set up which means that a full 3D model is required for detailed analyses of the problem
18. chieiauatduanecatiiedeneidiaeaclaselneetet A5 YIT RESEARCH REPORT VTT R 00446 11 4 32 1 Introduction PORFLO is a two phase flow simulation code developed at VTT for solving 3D problems in nuclear power plant thermal hydraulics Applications of the code thus far include the modelling of the secondary side of the Loviisa VVER 440 steam generators BWR fuel bundles in the frame of the BFBT calculation benchmark isolation condensers of the passive safety systems of BWRs particle bed coolability and the flows in the EPR reactor core The code is presently under active development at VTT An important objective in the future is to further develop the PORFLO modelling of flows in the EPR reactor downcomer lower plenum and core Especially the effect of lateral cross flow between the fuel elements would be an interesting research issue from the safety point of view because such flows tend to even out the temperature differences between the fuel assemblies This issue was investigated in the frame of the SAFIR2010 research programme within the TRICOT project and will be continued in the SAFIR2014 project KOURA In the future modelling of the behavior of passive safety systems is foreseen to be an important topic because of new types of nuclear power plants and the continuation of the modelling of heat exchangers in these systems would also be of interest Another long term goal of the code development is coupling the code to the thermal hydr
19. e indices 1 Velocity 2 Mass flowrate 3 Pressure 4 Volume fraction 5 Temperature type i index j index k index phase var 11 11 monitor 1 11 11 monitor 2 11 11 monitor 3 11 11 monitor 4 11 11 monitor 5 11 11 monitor 6 11 11 monitor 7 11 11 monitor 8 11 11 monitor 9 NN ooooo0oo0oo0oo0o0 S NWAUOONOO ARARARAAR AA VNNNNNNN FREE AEA inrtiaieitieitiaieiareiareitiartiaiaiareitinitinitit initiert ieitiaieitieitieitiareiareiaiei tiarasta eitinitini id In this section monitors that record the history of the selected variables can be set up The indices i j and k refer to the cells x y z whose values are to be saved in a monitor file monitors txt In the phase index 1 and 2 denote the liquid and gas phases respectively The values of the specified variables are saved each time step In the example above the volume fraction of gas is saved in nine cells at successive layers VIT RESEARCH REPORT VTT R 00446 11 16 32 FARE ee ee ANIMATION Se Number of variables saved for animation If this is set zero do not give any of the information below 5 Variable indices Phase indices 1 Velocity 0 All phases 2 Mass flowrate 1 phase 1 3 Pressure 2 phase 2 4 Volume fraction 5 Temperature variable phase 1 0 animation 1 2 0 animation 2 3 0 animation 3 4 0 animation 4 5 0 animation 5 Anim
20. eing the ability to model a specific phenomenon or a system the starting point for the selection of the physical models may be understood through the different applications Thus far the code has been utilized in the following applications VIT RESEARCH REPORT VTT R 00446 11 3 1 9 32 1 Isolation condensers Miettinen and Karppinen 2003 2 BWR fuel bundle and modelling of the NEA NRC BFBT benchmark Ilvonen and Hovi 2009 3 Horizontal steam generators research report and a conference publication by Hovi and Ilvonen 2010 4 Porous core debris beds Takasuo et al 2011 5 3D model of the EPR core modelling work has been started in 2010 but not yet published The cases deal with a multitude of flow configurations and heat transfer modes Thus each application requires a different selection of models for heat transfer frictional pressure losses and possibly turbulence For instance the frictional pressure drop in the interior of a densely packed particle bed is significantly greater than the pressure drop across steam generator tubes The closure models of the momentum conservation equations can be found in the code module named FlowSolution F90 The friction models for the drag forces between the solid and fluid phases and the interfacial friction are programmed as separate subroutines The user may modify these subroutines and determine the friction momentum exchange coefficients according to the needs of his her applic
21. eometry In the Data Set menu select the variable to plot Here we take the void fraction Alpha_g as the examined variable m StarNode 0 4 2 TOX File Edit Tools View Help Pi m A N i Bea XBO8 N Oe Model Explorer X 3D View Cross Section View 1 M Model gt 3D View PORFLO Object Cross Section View 1 PORFLO Object Cross Section 1 1 000e 00 ax PORFLO Object Cross Section 1 v a v Unit Visualization mode Nodal lt Use data mask False Mask data set None ask minimum Mask maximum 1 Default Automatic bounds False Use overall bounds True Minimum 0 0000000E 00 Maximum 1 0000000E 00 0 000e 00 OOB rendering Clamp Linked to original v True The Visualization mode menu presents options for interpolation and drawing contour lines Here we do not wish to interpolate the simulation data and select the Nodal mode The Use data mask button provides options for masking the data values based on selected minimum and maximum values The Color scale button provides options for changing the default color scale e g to grayscale and for setting overall global bounds for the color scale Here we take an overall bound from 0 0 to 1 0 for the void fraction by selecting the Use overall bounds option and setting the Minimum to 0 0 and Maximum to 1 0 as has been done in the figure above The global scale option is especially h
22. he grid consists of a pool region and a particle bed region Example input The control of simulation time time step size and the interval of generating output restart files are done in the input file named porflo dat along with the selection of numerical and physical parameters The input for the porous particle bed case is presented next with explanations of each section given below the sections FEE EAE A AA PORFLO v2 0 INPUT FILE FERRE AEE A AE FAHAHAH EHH GENERAL INPUT 4HA Restart mode 0 run from beginning 1 restart 0 Restart interval number of time steps The restart result file is written to a unique file at the end of the interval 2000 Launch Matlab 0 no 1 yes 0 Close the residual file after write 0 no 1 yes 1 YIT RESEARCH REPORT VTT R 00446 11 12 32 Range of residual plotting the number of iterations plotted 200 Gravity x comp y comp z comp 0 0 0 0 9 81 Fictional loss coefficient for FREE FLOW only open pool 0 0d 0 Superheat of the heater elements C 5 0 FAB HHRHH HHHHHRHRHRHHHHHHHHRHHHHHHHHHHHHHHHHH In the above section we first define if the calculation is restarted from a previous calculation the simulation parameters are read from an output file The restart interval gives the frequency of writing output files in time steps Residuals of the solution may be monitored during the calculations using Gnu
23. how axes selection 7 If necessary zoom the view by the mouse wheel and rotate by dragging the mouse while holding the right button 8 The animation control is found in the toolbar above the 3D View Use the control buttons to play stop rewind and forward animations Vurr RESEARCH REPORT VTT R 00446 11 A7 m StarNode 0 4 2 TOX File Edit Tools View Help S DODIY DORK A b BoA Model Explorer E i ee amp Model amp 3D View PORFLO object 1 000e 000 Properties a x ame PORFLO object Nodes in x direction 21 Nodes in y direction 21 Nodes in z direction 28 albha_2 Unit _ Fase 7 Use data mask False Default x Automatic bounds False Use overall bounds True Minimum 0 0000000E 00 Maximum 1 0000000E 00 OOB rendering clamp v Show axes 0 000e 000 9 Exporting animations to MPEG files is done by selecting File Export animation Type the file name click Save and select the output resolution bitrate GOP and the start and end time of the selection to be exported Click OK Resolution Bitrate kbps 3000 GOP 10 Start time 0 01
24. lations in which the aim is to detect dryout within the particle bed it is useful to observe the void fraction by plotting the saturation profiles within the particle bed during the simulations Saturation is the fraction of liquid within the pores s 0 a The profiles may be generated by a simple routine that reads the void fraction history from the monitor file monitos txt at VIT RESEARCH REPORT VTT R 00446 11 21 32 selected time step intervals Then the void fraction values can be converted to values of saturation and plotted as a function of the height of the geometry An example is presented in Fig 6 Axial saturation profile see input Timed Time2 Times Timed TimeS Time6 Time Time8 Latest Height m 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 Saturation Fig 6 Saturation profile in the simulation of a cylindrical particle bed 5 Post processing The main output of the code is written in text files as described in the previous Section for example porflo1234 txt that contain the three dimensional arrays of the simulation variables In addition to this the code prints several other output files The output files are listed below 1 Values of simulation variables porflo txt 2 Log file porflo log 3 User defined monitor file monitors txt 4 Heat transfer monitor file heat txt 5 Mass flux monitor file masses txt 6 Residual monitor file residuals txt
25. nitors of selected variables during the simulations have been included as an option in the input file 6 2010 7 Heat transfer models for pure conduction that include the calculation of effective thermal conductivity of porous medium have been implemented in order to examine the heat transfer inside and between different types of solids 8 2010 8 A possibility for explicit temperature solution which improves the convergence of some simulation cases has been included 8 2010 9 Several additional output options such as the heat transfer rates between the phases have been included 8 2010 10 The possibility to create animations of the simulation output by using the StarNode visualization tool has been included 8 2010 11 The possibility for a flexible selection of friction models for different regions of the computational grid has been included in the input file 9 2010 Reference B rger M Buck M Schmidt W Widmann W 2006 Validation and application of the WABE code Investigations of constitutive laws and 2D effects on debris coolability Nuclear Engineering and Design 236 2006 p 2164 2188 RESEARCH REPORT VTT R 00446 11 VYT APPENDIX B Examples of creating plots and animations in StarNode The following gives step by step instructions on how to generate 2D plots 3D plots and animations in StarNode The data of a PORFLO particle bed simulation is used to demonstrate the visualization process A Cartesian grid
26. of porous core debris beds The Authors YIT RESEARCH REPORT VTT R 00446 11 3 32 Contents Preface eie E E EE 2 AY ADR GCUCUOM cscniscicacnscsiccsscuttspnsccisnenssdabasubicubicnt bibbinh hasbbenl bishbinh babieukhaanbinh baabbeuketes 4 2 PORFLO Yo cl ane nee er Peet re ere nen eer en ee nen ee enn ern EE ee ee ten eee ere 5 3 Setting up simulations oscerecoxesiencnaitreccrprctenduetstaccuescieca stan aupnctencaeSienauetduanauasAencueres 8 3 1 Grid generation 22 eee eeececeee cece eee eeeeeeeeaaaeeeeeeeeeeeesaaaaaaaeeeeeeeeeeseesccaeaeeeeeeees 9 3 2 21151 91 414 9 0 eee ee Pre ee rr Poy ere ry ey ey me a reer nee ene mere 11 4 Running ot2 e 0 r g Fane ee OEP ne ee One n ORer em ACT 17 B POSIEOIOC SS SN enrian a R Ea AA EEA A ENE EEEE 21 6 Concluding 1S INTIS arsectcereistecesenenescisenee cameannsacneneistnavennnanuineudsemeennsoameultiastcnaasennees 23 FICISFONGES visccticeticcssdelcucsidelccnsidehosepidelesetidebisebidelisetiiebisetiielambiiebitebidelathiebiibiiebisnies 24 APPENDIX A List of PORFLO updates for the porous particle bed application in POO ee eE EEE sagsegcntecetendiosssasstebecede te E Nacoseqeeteiets A1 APPENDIX B Examples of creating plots and animations in StarNode A2 Creatng a ed Be a eereemcr ener nT e a e A AEAEE on near A2 Greating a 3D Plot eceisscc aces ce espa aa eases aia eaa dgelss acuta k a KKT an A4 Creating an animation fac sect cectdsaietincactstdeerantieccncn
27. olved This is used in modeling the COOLOCE experiments in which the effectiveness of heat transfer from the heating elements to the solid particles is estimated i e in this case two different types of solids are treated separately In addition to the calculation of heat transfer closure models are incorporated for the different drag forces between the phases and turbulence for which the standard k e model is under development For more information of the physical models see Hovi 2007 Hovi and Ilvonen 2010 and Takasuo et al 2011 A list of the main PORFLO updates in 2010 for the code development branch of the particle bed application is presented in Appendix A The iterative solution process of the PORFLO six equation model is presented in Fig 1 The pressure velocity solution is done by the SIMPLE algorithm Semi Implicit Method for Pressure Linked Equations originally developed by Patankar 1980 RESEARCH REPORT VTT R 00446 11 7 32 Case specific input amp initialization Particle BWR Isolation Steam 3D core bed bundle condenser generator Common input initialization amp restart Advance time step Solve pressure and volumetric flow distributions using the Phase Coupled SIMPLE algorithm Step 1 Solve the momentum equations for vapor amp liquid Step 2 Solve the pressure correction equations Step 3 Correct pressure and velocity fields Step 4 Solve phase volumes and calculate volume fractions
28. own dot2 3 136337596420553E 065 Possible breakdown dot2 3 136303949479932E 065 Possible breakdown dot2 4 818010700972901E 061 Eisen_CG_2 converged iter dotpo normr 62 1 865354666523802E 032 9 934854680066850E 017 TIME STEP 248115 ITERATION 3 sum_rhs 3 690748165034168E 010 max_rhs 1 203304296482077E 011 Scaled_VI 1 908508566455768E 007 Liquid mass flow out kg s 0 015 Vapor mass flow out kg s 0 015 Possible breakdown dot2 3 136328851929896E 065 Possible breakdown dot2 3 136306655695237E 065 Possible breakdown dot2 4 818010570857190E 061 Eisen_CG_2 converged iter dotpo normr 59 3 963100837722369E 033 4 372973551751188E 017 TIME STEP 248115 ITERATION 4 sum_rhs 2 342841975851242E 010 max_rhs 5 817554988088447E 012 Scaled_VI 1 160823559634645E 007 Liquid mass flow out kg s 0 015 Vapor mass flow out kg s 0 015 Possible breakdown dot2 3 136324136644908E 065 Possible breakdown dot2 3 136313744276104E 065 Possible breakdown dot2 4 818010806491714E 061 Eisen_CG_2 converged iter dotpo normr 62 1 710564400908876E 033 2 966982940673197E 017 TIME STEP 248115 ITERATION 5 sum_rhs 1 562905868600654E 010 max_rhs 3 575445061548832E 012 Scaled_VI 7 486190141817209E 008 VIT RESEARCH REPORT VTT R 00446 11 19 32 Liquid mass flow out kg s 0 015 Vapor mass flow out kg s 0 015 Total liquid mass 230 429381880713 Total vapor mass 1 801825595384579E 002 Liquid
29. plot for which the range of iterations to be plotted is given For this the option Close the residual file after write should be set to 1 In addition the following physical parameters are given gravity component fictional loss coefficient this is a friction coefficient given for the free flow of the pool volume to make the calculation numerically stable in cases in which the pool dynamics is not modelled in detail and no wall friction is taken into account and superheat of the heater elements The superheat is given in case surface temperature of the solid phase is constant FAH HA SOLUTION CONTROL 444 Minimum number of SIMPLE iterations per time step 5 Maximum number of SIMPLE iterations per time step 100 Is explicit Temperature Heat transfer solution used 0 no 1 yes 1 Maximum number of Heat transfer Temperature iterations 5 Maximum allowed norm of Temperature change 1 0d 10 Convergence criteria Sum of P Cor RHS Max of P Cor RHS 1 0d 8 1 0d 9 FABER The number of iterations and convergence criteria for the pressure velocity and heat transfer solutions are given in the section above Explicit temperature solution may be selected which means that the temperatures of the three phases are solved once in a time step otherwise temperatures are solved iteratively VIT RESEARCH REPORT VTT R 00446 11 13 32 within each SIMPLE iteration Explicit temperature solution
30. present the volumetrically heated conical COOLOCE particle bed inside a vessel that contains liquid and steam the red volume in the top section of the grid Velocity vectors of the gas phase in the same simulation are given in Fig 8 The time evolutions of different variables or their profiles at fixed simulation times e g with respect to the height of the geometry may be examined by using the monitors txt data file Time evolutions may be directly plotted and the other data may be sorted from the file according to the user s needs similarly to the example in Fig 6 0 Fig 7 Visualization by StarNode 2D cross section of void fraction in a particle bed simulation left and 3D maximum intensity projection of the void fraction in the same simulation right YIT RESEARCH REPORT VTT R 00446 11 23 32 0 35486 pp a Saal Popen o me EAS NE E vices a a i a a y 2 a a E a gt gt PPPPPr gt gt gt PDD PP ED DE soe ee CECH LET CES SO st aana vy PP gt gt gt gt gt gt gt gt gt gt gt gt es Ba SE PP PP PI 2 gt gt gt gt gt _ gt gt gt gt 9 9 9 gt eS A se eee _ _o 09 0 a 0 Fig 8 StarNode vector image of vapor velocity in a particle bed simulation Concluding remarks PORFLO is a 3D two phase flow simulation code which utilizes the porous medium approach in the modelling of flows in complex geometries The code is applied in the thermal h
31. s options for masking the data values based on Creating an animation 1 selected minimum and maximum values Start the StarNode software 2 Inthe program menu select File Import Model and select the appropriate binary file in this case animation bin Select the format of the data file PORFLO Binary Data and click OK to read the file Animations can be viewed in both 2D and 3D The Model Explorer window and the Properties window are similar as in creating 2D and 3D Plots see the previous sections In this example we create an animation that shows the void fraction as the maximum intensity projection of the variable YIT RESEARCH REPORT VTT R 00446 11 A6 4 Left click 3D View in the Model Explorer In the View rendering mode drop down menu select Maximum intensity projection m StarNode 0 4 2 TOX File Edit Tools View Help Pee SX XBOBIN ADP ODD bx Model Explorer X 30 View Model Y 3D View PORFLO object Properties Name 3D View View rendering mode Max intensity project w Legend 5 Left click the PORFLO object in the Model Explorer left click the Data set in the Properties window and select the void fraction in the drop down menu Alpha_g 6 Select the global bounds for the color scale by clicking the Color scale button and enabling the Use overall bounds selection Give 0 0 for the Minimum limit and 1 0 for the Maximum limit The axes may be turned on and off from the S
32. sists of the files listed in Table 1 An explanation of each of the modules is given Table 1 PORFLO source files File name Contents Parameters F90 Dimensioning parameters for meshes and the material properties for the fluid and solid phases OldRoutines f Fixed form source code from previous PORFLO versions Geometry F90 The routines for mesh generation and mesh based initial data i e conversion of geometrical data to a format readable by PORFLO LinearSolvers F90 Solution of the linear systems of equations Contains several preconditioned linear iterative solution methods such as CG and BiCGSTAB FlowSolution F90 Coupled solution of pressure and velocity fields the Phase Coupled SIMPLE algorithm ScalarTransport F90 Solution of scalar transport equations a general purpose scheme HeatTransfer F90 Heat transfer and temperature solution TestiMain F90 Main program input read and initialization the main iteration loop output write The PORFLO code has been applied to specific cases addressing two phase flow in complex geometries Because the code has been under continuous development during recent years it should be noticed that the applications utilize different versions of the code This report focuses on the code development in 2010 and the latest version that has been set up for the particle bed simulations in November 2010 However since the code development has been done with the aim b
33. that has been developed by VTT A brief review of the general solution methods utilized in PORFLO and the current status of the code is presented User instructions and guidelines on how to set up run and post process PORFLO simulations are also given Confidentiality Espoo 24 1 2011 Written by Reviewed by Accepted by p het Cote M Spel Fi vce Jead Eveliina Takasuo Elina Syrj lahti Timo Vanttola Research Scientist Research Scientist Technology Manager TRICOT Project Mana VTT s contact address PO Box 1000 02044 VTT Finland Distribution customer and VTT SAFIR2010 and SAFIR2014 Reference Group 3 VTT Timo Vanttola Eija Karita Puska Vesa Suolanen Jarto Niemi Pasi Inkinen SS ee E E E The use of the name of the VTT Technical Research Centre of Finland VTT in advertising or publication in part of this report is only permissible with written authorisation from the VTT Technical Research Centre of Finland yrr RESEARCH REPORT VTT R 00446 11 2 32 Preface The PORFLO code development and modelling work has been conducted mainly within the TRICOT project in the frame of the SAFIR2010 Research Programme on Nuclear Power Plant Safety http virtual vtt fi virtual safir2010 In 2010 significant support to the SAFIR2010 work has been provided by a self financed project which aims for training a new code user and extending the PORFLO applications to the coolability
34. tinuity equations for the liquid Eq 1 and gas Eq 2 are f e 1 a p Ot asap Ot V e 1 a pu 7 1 V cap u 7 2 where t is time s e is porosity Ug is vapor velocity m s uy is liquid velocity m s a is void fraction pg is vapor density kg m p is liquid density kg m and y is evaporation condensation rate per unit volume kg m s The momentum equations for the liquid Eq 3 and gas Eq 4 phases are Lela om y fe 1 a pu Jou e 1 a p e 1 a T 3 e 1 a pg Fpc Fp F olerem y capu u a Vp ea V T eap g Fpc Fp F 4 where p is pressure Pa T is the surface stress tensor N m Fr is the interfacial friction force N m Fpc is the momentum transfer due to phase change N m gt and F N m is used to describe other forces in the system such as drag between the fluids and solid particles in the case of particle beds The energy equations have the following form VIT RESEARCH REPORT VTT R 00446 11 6 32 d e 1 a ph Ot A eap h Ot V e 1 a p hu 9 5 V cap hu Q 6 where hg is vapor enthalpy J kg and is liquid enthalpy J kg The terms Q on the right hand sides represent the heat fluxes to and from the respective phase in the control volume These depend on heat transfer correlations which are application dependent In addition to the fluid phase temperatures conduction in solid phases can be s
35. to name the file porflo exe Most of the simulations have been run on a Linux cluster that consists of four computer nodes A typical running time for a particle bed calculation with 21 x 21 x 28 cells with no parallelization is 24h per 500 s of simulation time with a time step of 0 01 s It is often useful to save the output of running the simulation into a log file porflo log for e g tracking possible errors The log file contains the output from the initialization of the calculation and mesh generation as well as the numerical data that is printed each time step and iteration Note that in long simulation runs this can result in very large log files An example extract of the log file during one time step is given below VIT RESEARCH REPORT VTT R 00446 11 18 32 TIME STEP 248115 ITERATION 1 sum_rhs 1 054984973833832E 009 max_rhs 1 039213957942930E 010 Scaled_VI 6 462217459434782E 007 Liquid mass flow out kg s 0 015 Vapor mass flow out kg s 0 015 Possible breakdown dot2 3 136358206071463E 065 Possible breakdown dot2 3 136332456197489E 065 Possible breakdown dot2 4 818010376092232E 061 Eisen _CG_2 converged iter dotpo normr 62 5 502181000275844E 031 4 760181068825489E 016 TIME STEP 248115 ITERATION 2 sum_rhs 1 448735037399436E 009 max_rhs 4 790601964600738E 011 Scaled_VI 6 581468975922142E 007 Liquid mass flow out kg s 0 015 Vapor mass flow out kg s 0 015 Possible breakd
36. with the dimensions of 21 x 21 x 28 computational cells is used in the example simulation data Note that application specific choices may have to be made depending on the type of the data and the simulation code that has been used to generate it Creating a 2D Plot 1 Start the StarNode software 2 In the menu select File Import Model and select the appropriate file in this case porflo txt Select the format of the data file PORFLO Restart File and click OK to read the data file m StarNode 0 4 2 OX imi Edit Tools View Help E New Model Ctri N F Import Model Import Data Export Exit Import model from external data file 3 In the Model Explorer window on the left select PORFLO Object click the right mouse button and select Send To 2D View A 2D cross section of the data is displayed In the Model Explorer click PORFLO Object Cross Section 1 to access the 2D Plot options These are shown in the Properties window below the Model Explorer YIT RESEARCH REPORT VTT R 00446 11 A3 4 The 2D Plot can be zoomed in and out by the mouse wheel 5 6 8 In the Direction drop down menu select the direction axis X Y Z for the cross section that you wish to visualize In the Index menu select the index of the grid cells in the direction to be visualized In this case we choose the central plane in the X direction whose index is 11 and get a vertical cross section of the modeled g
37. wn dot2 2 268180854958074E 109 Possible breakdown dot2 6 255205928786866E 057 Possible breakdown dot2 7 662697143800874E 099 Possible breakdown dot2 3 136319245473636E 065 Possible breakdown dot2 3 136323485404765E 065 Possible breakdown dot2 4 818011341200079E 061 Eisen_CG_2 converged iter dotpo normr 58 8 741532365392332E 031 5 541497706632693E 016 Gnuplots scripts have been generated that can be used for follow up of the residuals and heat transfer rates during the simulations Plotting of the residuals in real time can be used to help detect convergence problems Examples of residual and heat transfer plots are presented in Fig 4 and Fig 5 Heat transfer monitors are especially useful in detecting the contributions of different heat transfer mechanisms to the overall steady state transient behavior of the modelled system VIT RESEARCH REPORT VTT R 00446 11 20 32 Scaled Residuals 100 0 01 0 0001 1e 06 Residual 1e 08 1e 10 1e 12 1e 14 Iteration Fig 4 Convergence of the calculation is monitored by plotting the residuals of the variables each time step Heat Transfer Rates Heat Transfer Rate kl EAr EE ATA E iar a ee 0 500 1000 1500 2000 2500 3000 Time s Fig 5 Example of time evolution of the heat transfer rates in porous particle bed a system which consists of heaters solid particles liquid and vapor that exchange heat In the particle bed simu
38. ydraulic safety analysis of nuclear power plants In recent years the code has been under active development at VTT for the following applications core debris coolability secondary side of steam generators flows across fuel bundles and the EPR reactor core Extensions of the PORFLO applications to e g modelling of passive safety systems are planned in the future Another long term goal is to connect the code to the family of system codes and reactor core simulators TRAB 3D SMABRE that have been developed by VTT Review of the solution methods and structure of the PORFLO code version of 2010 were presented and general guidelines on how to set up and run PORFLO simulations were given It was emphasized that the process of setting up simulations is application specific and editing of the source code is often necessary While this requires some skill in programming and understanding of the source code it allows significant flexibility in modifying of the code to suit different applications and cases Examples of post processing the simulation data by using the StarNode visualization tool were given The presented input output and visualization examples were based on the code version modified for the core debris coolability application in 2010 YIT RESEARCH REPORT VTT R 00446 11 24 32 References Gnuplot homepage http www gnuplot info July 20 2010 Hovi V 2008 Calculations of Boiling Two Phase Flow Using a Porous Media
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