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Aqwa User`s Manual

1. Symbols Purpose S ete Q Q Q ga ae View manipulation iy ic Selection control File shortcuts Show hide element boundaries EL zi Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates Ke N The Aqwa Editor User Interface Purpose Add a Comment to the selected tree object Add a Figure or Image to the selected tree object Control the output of the Report Preview results Purpose Turn on off highlighting of objects selected in the tree Show hide the sea and sea bed Solve f Solve Hydrostatics Over ahoiteutg The tree and the details are where the objects that are used to define the modelling requirements are organized Depending upon the selection in the tree a detail pane normally located below the tree will show the details of the selected object Symbols are shown next to each object in the tree to indicate its state Hydrodynamic Diffraction E Model A3 The Part is used to apply Geometry _ ii properties to each structure a Ship A ye Ship A AboveWater Gp Ship A Wales Bodies make up the part v Under defined in DesignModeler J Point Mass Ship B ye Ship B Underwater v amp Daina AQWA specific geometry EM o Point Ham based objects v Hydrodynamic Dif
2. An example of a WHT file is shown below This is an example of a wht file DEPTH 30 0 G 9 81 DIRECT X_REF ION 0 0 100 0 Y_REF 0 0 NAME EXAMP LE CURRENT_SPEED 0 6 CURRENT_DIRECTION 90 TIME 0 0000 0 2366 0 4732 0 7098 0 9464 1 1830 1 4196 1 6562 1 8928 2 1294 2 3660 2 6026 E WAVE HT s m 1 088 1 188 1 268 S16 351 1 427 1 471 1 494 1 476 1 406 Sla 1 149 0 966 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 55 Approach 2 7 8 Irregular Wave Group The Irregular Wave Group allows you to include multiple irregular waves in your analysis To insert a wave group right click on the Hydrodynamic Time Response object and select Insert gt Irregular Wave Group or click on the Hydrodynamic Time Response object and from the Analysis toolbar select Irregular Wave gt Irregular Wave Group After the wave group object is inserted right click on it and select Insert gt Irregular Wave gt wave type or click on the wave group object and from the Analysis toolbar select Irregular Wave gt wave type Define the options of each individual wave spectra in the group after you add them Note Although you can add multiple irregular wave groups and individual irregular waves you must have only one active in order for the analysis to solve the others must
3. Note It is not yet possible to employ symmetry in the Aqwa Editor hence the full model must be meshed 2 2 3 Add Fixed Points A Fixed Point is a non moving point defined as part of your geometry Fixed connection points are defined in the Details panel by entering coordinates in global space or specifying an offset from a vertex on a structure The coordinates defining the connection point can be parameterized A fixed point does not move with any structure even if it is initially defined as offset from a point on a structure A fixed point can be used by more than one object cable fender etc if required The option to choose a fixed point vs connection points on structures is controlled by the Connectivity field in the Details panel of the object using the connection points To add a fixed point click on the Geometry object in the tree and from the Add menu in the toolbar or the right click menu select Fixed Point Click on the Fixed Point object that was added and do one of the following Set Definition of Position to Coordinates and set the Position Coordinates X Ordinate Y Ordinate Z Ordinate in the Details panel Set Definition of Position to Vertex Selection Click on Select a Single Vertex in the Vertex field select a vertex on a structure and click Apply You can then set an X Offset Y Offset or Z Offset from the vertex if needed Note It is assumed that fixed points are on the sea bed for catena
4. Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 14 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior the structure and the water This means that the current coefficient should still be input even when there is no current present as the relative velocity is generally non zero for a dynamic analysis To add a Current Force Coefficients object 1 Select a part in the Tree Outline 2 Right click on the part and select Add gt Current Force Coefficients or Click on the Add icon in the toolbar and select Current Force Coefficients from the dropdown list A Current Force Coefficients object is added to the part 3 Select the Current Force Coefficients object in the Tree Outline and enter the coefficients in the Coefficient Data window that appears below the model Enter the Direction of the current 180 to 180 degrees the X force coefficient Translation X Y force coefficient Translation Y Z force coefficient Translation Z Rotation about X coefficient Rotation X Rotation about Y coefficient Rotation Y and Rotation about Z coefficient Rotation Z The number of rows is increased as each entry is made up to a maximum of 41 rows Note that the forces are in the directions of the axes not in the direction of the current For example for relative current velocity V in direction force in X direction CUFX V force in Y direction CUFY
5. k2 c k3 e for 0 lt ermax or EA e EA Egmax k1 2 k2 tmax 3 k3 Etmax E Ctmand for gt Etmax where EA c EA as a function of strain EA const the stiffness value input above k1 k2 k3 Nonlinear axial stiffness coefficients e linear strain 6L L Etmax Strain at Tmax Tmax maximum tension specified above For Cable Dynamics analyses the following optional additional data may be input Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 24 of ANSYS Inc and its subsidiaries and affiliates Define Connections The Bending Stiffness El The Bending Stiffness is specified in terms of El where E is Young s modulus and is the 2nd moment of area of the line The default value is zero The Added Mass Coefficient Ca Added mass is calculated by p Ca A per unit length in which p is the water density and A is the equivalent cross section area In other words the added mass is equal to the displaced mass of water multiplied by Ca For cable dynamic analysis the equivalent cross section area A must NOT be omitted The default is 1 0 The Transverse Drag Coefficient Cd Transverse drag force is calculated by 0 5 p Cd V2 De per unit length where V is the relative transverse velocity The default is 1 0 The Equivalent Diameter De for drag This allows the drag to be based on a different diameter from the added mass The default is
6. 2 5 1 Basic Global Mesh Options ccccsesssscccccceeceeseennaceeeeceesseessnsneeceeeeeseeessnneeeeeeeseseeesenaaeeeeeeens 37 2 5 2 Advanced Global Mesh Options ccccesessecccceceeeeeessneeeceeeceeeeessnaeeceeceeseneesaeeeeeeeseeseeeennaees 38 25 2 1 M sh ParaMeters xs c2ccc ssseeueethdescngsteouoiacd a a a E a aE GatecsnctudeeesGeasceceetecessicadethass 38 PRPA ANEA A EE A EE NA A A 38 2 52 33 Nila ti Noe EE EEE R E EEE E E a 38 25 24 Defeat rinNg ienna a e a a a a a a a 39 2 5 2 5 Generated Mesh Information cssscccccceccessessnnceeeeceesscessnneeeeeeeeseseesnaeeeeeeeeeeeeesaaees 39 2 5 3 L cal Mesh Controls kenna a a aAa e Eei Ea E RAAR A EES AA aR EAE 39 255 Di SIZIMG CONTON dni ee a KE e E AE AE A A E AK i 39 25 32 PINEHING CONTO ken m aae ea a a aa E E AAEN 39 25 33 nflation CONUIO aisne an e thes AE A E A EE E E EEA 39 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates iii User Manual 226 Establishy Analysis Settings svcuvsaaamune aaa arcpsuoundpauslesoayehireatiaady daewnus e a a E R Ea E ta 39 2 6 1 TIME Response Options ereenn inia ER EEEE EE EE EE E ERA ENEKE 40 26 2 OUTPUT File OPTIONS cei iei na E E E E REE ERE O E a tcares 40 20 3 OTF ODIOMS o Aane aiea a E A esae E AEA A EA IE Eea AEE DEAE EAA E A a 43 2 6 4 COMMON Analysis OPTIONS sisene eorne tisy isaret eavasaie
7. Inc and its subsidiaries and affiliates Setting Aqwa Application Options Current Define Current information Wind Define Wind information Cable Winch Define a Cable Winch Cable Failure Define a Cable Failure Solution Insert Result Display Hydrostatic Display Hydrostatic Results Hydrodynamic Graphs Display Hydrodynamic Graphs Pressures and Motions Display Hydrodynamic Pressure and Motion Results There are either one or two other windows shown depending upon the state of the analysis or tree item that is selected The main window which generally shows the model either geometry or mesh views in the Geometry tab Hydrodynamic results in the Graph tab a report of your analysis in the Report Preview tab and Hydrostatics results in the Properties tab where you can view text based results The secondary window which is used for displaying messages controlling the results and entering data This will appear automatically depending upon the tree item selected Messages are also dis played in the Messages view of the Project Schematic Hydrodynamic Diffraction ANSYS AQWA HYDRO DIFFRACT Fie Edt vew Unts Hep p 9 F D a ATEL St QQaQaGHQatn 9 Ba Geometry 3 3 Setting Aqwa Application Options Once you have created your Hydrodynamics analysis system and attached a geometry you can open the Aqwa Editor and set some options 1 Select Edit gt Options from the Aqwa Editor window
8. Inc and its subsidiaries and affiliates 5 Approach to define the geometry there are a number of aspects that you should consider to ensure that your model is suitable for analysis with Aqwa such as e Ensure that the model is split at the water line which must lie on the XY plane Import or create each structure use Translate operations to set the correct draft or depth for each structure and then use a Slice operation to split the surface bodies at water level e When using lines to create beams only tubular sections are supported in Aqwa all other sections will result in a stub element being formed and you will need to define additional information in the Aqwa application Lines should be created using Add Frozen Operation on the Line Details and consist of only 1 Point Segment per line e Each vessel structure should be a part so all the bodies that you have should be grouped via the multibody part facility Note it is not possible to rename these within the Aqwa application The model is oriented with its Z axis vertical up Surfaces must have normals pointing outward Hydrodynamic analysis systems only process the Line Bodies and Surface Bodies in a geometry By default Line Bodies are not imported with the geometry To change this default setting in the Workbench window select Tools gt Options and click on the Geometry Import entry in the tree Make sure that the boxes are checked for Solid Bodies Surface Bodi
9. Include Diffracted Wave Include Radiation Wave Include Hydrostatic Differential Include Second Order Terms Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 88 of ANSYS Inc and its subsidiaries and affiliates Solution The Structure Contour Type can be set to Interpolated Pressure Air Gap Resultant Displacement or None Above Water Body Display allows the visualization of the above water bodies to be set to Dimmed or Zero Pressure Pressure Measurement can be set to Force Area or Head of Water If set to Head of Water you can set the Wave Contour Type to Wave Height or None It is possible to visualize the distance between the sea surface and any point on the structure using the Air Gap selection in the Structure Contour Type field the results are plotted on the structure with positive numbers indicating that the structure at that position is above the sea surface If required the contour legend can be adjusted to represent a solid color above or below a given value If only the second order component is shown the Air Gap will be shown as zero The sea mesh size can be altered via the Analysis Options Sea Grid Size Factor setting The sea mesh extends throughout the structure however the results that are presented within dry areas are not ac curate The Minimum Value and Maximum Value of the results are shown and can be parameterized 2 8 4 Time History Motion Re
10. Model A3 F J Geometry Commections ve Catenary Data Mesh Jal Hydrodynamic Diffraction A4 vi Analysis Settings JB Gravity ve Structure Selection vy Wave Drections v Wave Frequences A Solution A5 2 Pressures and Motions 4 Details Details of Pressures and Motions Name Pressures and Moons Structure fiter N inctude interactn Yes Result Selection 2 Sec Auto Frequency 0 096 Hz Orecton 180 1 00 incident Wave A 1m Resutt Type Cycic i Wave Position P_ Range Number of Steps 12 Contour Selection Structure Contou Iimterpotsted Pressure Above Water Bo Ommed Pressure Messu Head of Water Weve Contour T Derim Wire Height a amp a o 638 6 Press Fi for Help Length units m A number of results can be presented in this manner by default the wave height and the interpolated pressure are shown It is only possible to plot wave contours when the structure contour type is com patible To achieve this the result must be plotted on nodes and must be a displacement type result The interpolated results are determined from the panel element pressures that are generated from Aqwa Any combination of wave components can be enabled and disabled to enable visualization and checking of the results To display a particular component set its corresponding field in the Component Selection section of the Details panel to Yes Include Incident Wave
11. Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 95 Workbench Interface 2 3 Expand the Aqwa Applet item in the tree Select the Analysis entry This panel allows you to set the following Solver options Aqwa executable location location of the executable file for the Aqwa solver You should not have to change this from the default setting Severity to force showing of messages level of error messages that will cause reporting to the Workbench Message pane Select the Units entry This panel allows you to set the following Default Units options Length Unit Force Unit Angular Unit Mass Unit Frequency Unit When you are finished click OK Click Cancel to abort your changes Note Option settings within a particular language are independent of option settings in another language If you change any options from their default settings then start a new Workbench session in a different language the changes you made in the original language session are not reflected in the new session You are advised to make the same option changes in the new language session 96 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates Chapter 4 Aqwa Common Features There are a number of feat
12. abet Swecten 3 380 2 087 aon lt a man gt Men no nie 4 ese ttt son s wl hee Siss 2 088 2 gt Ses N rm TET j a o as ai an ana 2273 m 98250 z som O53 on nN asse oses E mo esus son 1 428 mao mm Me new ane s295 924755 7 0055 203 9337 ERSTE SARRRRREREEEESS EEFE suy EE Prem P1 for reto Length unte m 2 8 2 1 Hydrodynamic Diffraction Results The following graph types for the Hydrodynamic Diffraction Solution object are available from the Hy drodynamic Graphs menu on the Insert Results toolbar 2 8 2 1 1 Diffraction Froude Krylov Diffraction Froude Krylov Linearized Morison Drag and Total Exciting Force Including Morison Drag 2 8 2 1 2 Response Amplitude Operators RAOs and RAOs with Linearized Morison Drag 2 8 2 1 3 Radiation Damping amp Added Mass 2 8 2 1 4 Steady Drift 2 8 2 1 5 Sum QTF and Difference QTF 2 8 2 1 6 Splitting Forces 2 8 2 1 7 Bending Moment and Shear Force 2 8 2 1 1 Diffraction Froude Krylov Diffraction Froude Krylov Linearized Morison Drag and Total Exciting Force Including Morison Drag Result Description 2D or 3D graphs to illustrate how these forces moments or the corresponding phase angle change with direction frequency or both direction and frequency Total Exciting Force Including Morison Drag is the sum of the already existing forces FK Diff and the additional Linearized Morison Drag p 44 Rele
13. data_start After the data start the first column contains time and subsequent columns in sets of 6 indicate the forces for specified structures The forces are ordered as follows using global directions X Y Z RX RY RZ The numbers in the XFT file are in a free format and can be separated by spaces An example of the data in a file would be structures 1 data_start 0 0000 4 4800EF 05 5 0400E 06 3 1360E 06 5 0400E 07 8 9600E 06 1 5120E 08 0 5000 4 3978E 05 4 9689E 06 3 0784E 06 4 9689E 07 8 7956E 06 1 4907E 08 1 0000 4 1592E 05 4 8207E 06 2 9114E 06 4 8207E 07 8 3183E 06 1 4462E 08 2 7 6 Regular Wave The Regular Wave object is used for Time Response analyses Regular Waves can only be applied when the Analysis Type under the Time Response Analysis Setting object is set to Regular Wave Response rather than the default value of Irregular Wave Response If a parameter is selected it will appear in the Workbench Parameter Set To insert a regular wave click on the Hydrodynamic Time Response object and select Insert gt Regular Wave or select Regular Wave from the Analysis toolbar Set Wave Type to Airy Wave Theory or Stokes 2nd Order Wave Theory for the calculation of the Froude Krylov forces Airy Wave Theory is not recommended to model big waves Enter the Direction and Amplitude of the wave The direction is shown in the graphics with an arrow light blue Enter a Period or Frequency for the wave The period frequency
14. given by ag 2 at Slad seed 3 4 ae where a a constant decided by H wp and y g acceleration due to gravity peak frequency y peak enhancement factor 2 7 7 2 Pierson Moskowitz The Pierson Moskowitz spectrum is formulated in terms of the two parameters of Significant Wave Height H and average Zero Crossing Period wave period T This is considered of more direct use than the classic form in terms of the single parameter wind speed or the form involving the peak fre quency where the spectral energy is a maximum The spectral ordinate S at a frequency w in rad sec is given by 2 2 so Fe 22 e z 24 The average i e mean zero crossing wave period Zero Crossing Period and Significant Wave Height are the parameters used to describe the Pierson Moskowitz wave spectrum the special case for a fully developed sea 2 7 7 3 Gaussian The standard Gaussian spectrum is given by S f E2 ME Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 52 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces where H is significant wave height fp is peak frequency o is standard deviation The Peak Frequency Significant Wave Height and Sigma c are the parameters used to describe the Gaussian wave spectrum The maximum value of o is capped at 0 08f 2 7 7 4 User Spectra 1D This
15. 5 4 33 4 4 45 7 oA Additional rows can be added to the end of the table and they will be automatically re sorted once entry is complete Velocity data can also be copied and pasted from an appropriate external source The time defined in the table rows does not need to match the time steps defined in the analysis the program will interpolate the wind speed and direction when necessary using a cubic spline interpolation technique When modeling periods of constant wind velocity adequate data points must be provided to satisfy the interpolation method Defining the WVT File Comment lines beginning with can be placed at any point in the file Before the data defining the time and wind velocities directions there must be a line containing only the text data_start After the data start for each line the first column contains time in s the second column wind speed in m s and the third column is wind direction blowing towards in degrees The numbers in the WVT file are in a free format and can be separated by spaces There is no limit on the length of the WVT file Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 66 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces The following is an example of data from a WVT file data_start 0 0000 8 0000 90 0000 0 5000 7 8532 88 7310 1 0000 7 4271 86 0840 2 7 11 Cable
16. Approach Note that although only 1 user defined wind spectrum is input the frequency coefficient and turbulence intensity can be specified as different for each spectral combination waves and wind Note also for a user defined spectrum there is no assumed mean wind speed profile The echo of the wind spectrum in the printout therefore shows the wind speed at the standard reference elevation of 10m to be the same as the mean wind speed input by the user 2 7 10 6 Time Dependent Velocity A time history of wind velocity can be defined directly in a table or by importing the information from an existing WVT file To define the data directly in the table select Insert gt Wind gt Time Dependent Velocity gt Manual Input To read the data from a file select Insert gt Wind gt Time Dependent Velocity gt Import WVT File Note After the data is imported no record of the file used to import the data is retained For Manual Input enter in each row of the table in the Data panel the Time and the Velocity and Direction of the wind at that time The time must be positive The first entry should match with the start time of the analysis The number of rows is not limited Ik gt Detats a Detais of Wind Nye wind vsb ty Visible Actrvity Not Superessed h Geometry AReport Pr Wind Spectral Definition Wind Defination Data Spectra None Time Dependant Teme s Veloctty mvs Owrection 4
17. Description 4 3 1 Deck Header 4 3 2 MATERIAL PROPERTY Card Line Bodies Point Mass Point Buoy ancy Disc 4 4 Deck 4 GEOM Geometric Properties 4 4 0 General Description 4 4 1 Deck Header 4 4 2 GEOMETRIC Property and CONTINUATION Card Line Bodies Point Masses Point Buoy ancy Disc 4 5 Deck 5 GLOB Global Parameters 4 5 0 General Description 4 5 1 Deck Header 4 5 2 DPTH Card Optional Water Depth Geometry 4 5 3 DENS Card Optional Water Density Geometry Gravity 4 5 4 ACCG Card Optional Gravitational Acceleration 4 6 Deck 6 FDR Frequencies and Directions Table 4 6 0 General Description 4 6 1 Deck Header 4 6 2 FREQ PERD HRTZ Card Frequencies Periods at which the Parameters are Defined Wave Frequencies 4 6 3 DIRN Card Directions at which the Parameters are Defined Wave Directions 4 6 4 MVEF Card Move Existing Freq Parameters Not Supported 4 6 5 DELF Card Delete Frequency Parameters Not Supported 4 6 6 CSTR Card Copy from Structure Number Not Supported 4 6 7 FILE Card Copy from File Unit 4 6 8 CPYF CPYP CPYH Cards Copy Freq Param s Not Supported Not Supported 4 6 9 CPYS Card Copy Stiffness Matrix Not Supported 4 6 10 CPDB Card Copy Data Base Not Supported 4 6 11 FWDS Card Define Forward Speed Wave Directions 4 7 DECK 7 WFS Wave
18. Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 1 2 Response Amplitude Operators RAOs and RAOs with Linearized Morison Drag Result Description 2D or 3D graphs to illustrate how the amplitude and phase of the structure response change with wave direction frequency or both direction and frequency You can view RAOs and RAOs taking into account the linearized Morison drag effects if Linearized Morison Drag p 44 is specified Plot availability e Line graph presentation Phase Angle plotted against either Direction or Frequency e Line graph presentation Distance Rotation plotted against either Direction or Frequency Surface graph presentation Phase Angle plotted against Direction Frequency Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 75 Approach Surface graph presentation Distance Rotation plotted against Direction Frequency The Frequency Scale can be modified to be Period Scale if required Line Graph Input Use the Component input to select which degree of freedom to plot either X Y Z for translation or RX RY RZ for rotation e When the plot is performed against Direction then the required frequency can be chosen using the Fre quency input e W
19. Mass Details Point Buoyancy Define Point Buoyancy Details Disc Define Disc Element Details Additional Stiffness Define Additional Stiffness Matrix Details Additional Damping Define Additional Damping Matrix Details Additional Added Mass Define Additional Added Mass Matrix Details Current Force Coefficients Wind Force Coefficients Define Current Force Coefficients Define Wind Force Coefficients Connections Insert Cables and Catenary Data Cable Define Cable Catenary Data Insert Catenary Sections and Joints Catenary Section Define a Catenary Cable Section Catenary Joint Define a Catenary Buoy or Clump Weight Connection Stiffness Define Connection Stiffness Matrix Mesh Define and Generate a Mesh Mesh Sizing Refine an area of the Mesh Analysis Name of Analys is Define Analysis Type and Name Analysis Settings Define Analysis Options Structure Selection Define Structures to be Analyzed Gravity Define Gravity for the Analysis Wave Directions Define Wave Direction Ranges Wave Frequency Define Wave Frequency Ranges Structure Force Define a time history of Structure Forces Regular Wave Irregular Wave Define a Regular Wave Define an Irregular Wave Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 94 of ANSYS
20. RAOs with Linearized Morison Drag wid ud ET E T A E E E E TT 75 2 8 2 1 3 Radiation Damping amp Added Mass ssssssssssessesseessssressssseessssrrssssreesssrressssreesssee 76 2 8 214 Steddy Drift oorno e e E a aae eE E E e a a e Nae 77 2 8 2 1 5 Sum QTF and Difference OTP s sssssessssssesssssessssrressssresssereessssrersssressseresesereessssress 77 28 2 16 Splitting FOTCE Sienan ii a e a a a ara aeaa 78 2 8 2 1 7 Bending Moment and Shear Force sssssessssssessssseesssreessssreessssresssereesssreessseeesssrress 79 2 8 2 2 Hydrodynamic Time Response Results iscsusnessdacadivesscotwasdedsasvapsdansvanecadavendconstasacoddvavands 81 28 22 1 Struct re PoSitioN s seesinane a a AE e a EE EE AES e aea 81 2B 2 22 Str ct re Velocity rse e aia AR A EEE EE T N a 82 2 8 2 2 3 Str ct re Acceleration e aaa Clea da ieie cae a a ei a aed oiean aay 82 2 8 2 2 4 Struct re FOICES israse EEE E EEA E ETE EE E E 83 2 8 2 2 5 Fender Forces neresine inae ai ie N E i e S Eana 85 28 220 JOU FONCES eiie ariete ienai a AEEA AR EEA aE 85 28 22 PAIS FOrC S sd sg e ai i ai aA a a bad gy aa Sunda aa E ieaie 85 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates User Manual 2 8 2 2 8 Time Step Erro ersi ns osise r eE e E TENNE EEE TEE ORE 86 2 8 3 Hydrodynamic Pressures and Motions Results ccsssscccccceesssessnneee
21. Starting Conditions LIBRIUM Analysis Settings 4 17 Deck 17 HYDC Hydrodynamic parameters for non dif _ Analysis Settings Parts Structures fracting elements 4 18 Deck 18 PROP Printing Options Not Supported 4 21 Deck 21 ENLD Element and Nodal Loads Not Supported All Aqwa Wave commands Not Supported 6 2 Transferring Pressures and Motions Frequency Domain to Mechan ical Models Pressures and motion effects of a rigid body modelled during the Hydrodynamic Diffraction Analysis can be applied to ANSYS Mechanical APDL for further analysis Static or Transient analyses are performed in ANSYS Mechanical APDL using a specified phase angle to obtain the results from the frequency domain based hydrodynamic diffraction analysis For further details see Applying Ocean Loading from a Hydro dynamic Analysis in the Mechanical APDL Advanced Analysis Guide which details the methodology used in Mechanical APDL to achieve this Note It is not possible to transfer pressure and motions from a hydrodynamic time response ana lysis to ANSYS Mechanical APDL The ocean wave loading requires the results from the hydrodynamic diffraction analysis to be generated in a text file format This can be achieved by running the AQWA2NEUT program after the hydrodynamic diffraction analysis To run AQWA2NEUT use a command of the form assuming that the executable is on path and the Aqwa database files are in the running di
22. Submerged Structure Detection is Program Controlled by default and Aqwa will detect the highest point greatest Z coordinate and check whether it is below the water level alternatively this automatic detection can be overridden The Metacentric Heights can be overridden about both the global X Override Calculated GMX Yes or Y Override Calculated GMY Yes axes to modify the hydrostatic stiffness of the vessel When these are overridden Aqwa first calculates the hydrostatic stiffness matrix based only on the cut water plane and displaced volume properties It then adjusts the second moments of area IXX lYY and recal culates its associated properties PHI principal axis GUX GMY BMX BMY etc to give the required GM values The associated additional hydrostatic stiffness is calculated automatically and stored in the hy drodynamic database If the GM value input is less than that based on the geometry alone the resulting additional stiffness will be negative This would be the case if ballast tanks were being modelled making the structure less stable statically Nonlinear roll damping moment can be calculated in slow drift time history analyses to take into account the effect of vortex shedding from the bilges of a vessel The method is based on An Engineering As sessment of the Role of Non linearities in Transportation Barge Roll Response Robinson and Stoddart Trans R I N A 1986 Whether vortex shedding is occurring or not is calc
23. Time Response Systems p 101 shows two connected Hydrodynamic Time Response systems Figure 5 1 Connected Hydrodynamic Time Response Systems v A v B v 2 Geometry Y E2 i Geometry 4 2 Geometry v Geometry 3 wy Model y 3 w Model o y 4 R2 Setup 4 4 t Setup y 5 Ws Solution 7 5 Solution F f 6 B Results F 6 Results F Hydrodynamic Diffracion Hydrodynamic Time Response Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 101 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 102 of ANSYS Inc and its subsidiaries and affiliates Chapter 6 Aqwa Appendix 6 1 Information for existing Aqwa users If you are familiar with the Aqwa data files and help system then you can use this section to find where an existing command is located in the Aqwa Editor tree objects Table 6 1 Cross reference of tree objects with Aqwa commands Aqwa Manual Reference Aqwa Editor Tree Object 4 0 Deck 0 Preliminary Deck 4 0 0 General Description Project 4 0 1 JOB Card Analysis 4 0 2 TITLE Card Project 4 0 3 OPTIONS Card Analysis Settings 4 0 4 RESTART Card Analysis 4 1 Deck 1 COOR Coordinate Positions 4 1 0 General Description 4 1 1 Deck Header 4 1 2 COORDINATE Card Mesh Mesh Si
24. V moment about Z axis CURZ V where CUFX CUFY and CURZ are the coefficients Similar equations apply for force in Z and moments about X and Y The coefficients are applied in a moving axis system in other words the axes move with the structure Since there is no structure local axis system available the initial coefficient data must be defined relative to the global coordinate system when the structure is in the position as defined in the geometry For example Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 15 Approach CUFY gt as CUFY chs Y Position Defined in the Geometry curt Global Coordinate 4a Sysetm cut Position During Simulation Note You may have multiple Current Force Coefficient objects in the analysis but only one can be enabled during an analysis an error will be reported when solving if multiple objects are en abled e There is a limit of 41 unique directions for the enabled Wind Force Coefficient and Current Force Coefficient tables combined Each table may have an entry for the same Direction value e If a direction is specified for Wind Force Coefficients that does not exist for Current Force Coefficients then linearly interpolated values will be utilized for the Current Force Coefficients for that direction based upon adjacent defined directions Release
25. Winch Two types of winch can be applied to a cable a winch that can wind in or pay out as required to maintain a constant tension in the cable a winch that can wind in or pay out at a given rate to lengthen or shorten the line To add a Cable Winch object click on the Hydrodynamic Time Response system then select Cable Winch from the Analysis toolbar or from the right click menu Insert gt Cable Winch You can then configure the type of winch you want 2 7 11 1 Winch that Maintains Constant Tension 2 7 11 2 Winch that Changes Cable Length 2 7 11 1 Winch that Maintains Constant Tension Cable winches that maintain constant tension can only be used with Linear Elastic or Non Linear Poly nomial cables In the case of a constant tension winch friction coefficients during the winding in Fw or paying out Fp process are required hence the tension in the winch mooring line when winding in is given by Tw Ts 1 Fw where Ts is the winch tension specified When paying out the winch tension is given by Tp Ts 1 Fp For example if the tension specified is 1000 tonnes and Fw and Fp are 0 3 and 0 1 re spectively then the tensions will be 700 and 1100 tonnes respectively The initial tension is undefined The default initial tension is the winding in tension i e 700 tonnes in the example above The winding in friction coefficient should be specified as negative if the paying out value of tension is required as the initial tension Th
26. You may have multiple Wind Force Coefficient objects in the analysis but only one can be enabled during an analysis an error will be reported when solving if multiple objects are en abled There is a limit of 41 unique directions for the enabled Wind Force Coefficient and Current Force Coefficient tables combined Each table may have an entry for the same Direction value e If a direction is specified for Current Force Coefficients that does not exist for Wind Force Coefficients then linearly interpolated values will be utilized for the Wind Force Coefficients for that direction based upon adjacent defined directions Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 18 of ANSYS Inc and its subsidiaries and affiliates Define Connections An error will be reported if there are multiple entries having the same value of Direction in the table 2 3 11 Structure Connection Points A structure Connection Point is defined as a connection point attached to a Part that moves with the Part Connection points are defined in the Details panel by entering coordinates in global space or specifying an offset from a vertex on a structure The coordinates defining the connection point can be parameterized A structure connection point can be used by more than one object cable fender etc if required The option to choose a fixed point vs connection points on structures is controlle
27. a iE EE SE E a 62 2 7 10 4 ISO Standard Spectrum n oeiensinraro in ensien eai EE ia E EE a E Ea 63 2 7 10 5 User Defined Spectrum cccccccccessssssneeceeeccesssessnaneeececeeesesennneeeeceeseseeeseaeeeeeeeeseseeees 63 2 7 10 6 Time Dependent Velocity ssesseseessseeessssseessssressssseesssstesssereessssresssereesssetesssereesseseessse 66 27e MARU VV MING IA eu oe erlang nean staan Levant ay a a i Shihan Bahan Ee ea eaa aa aa 67 2 7 11 1 Winch that Maintains Constant Tension ccsssseccccceceeseessneeceeeeeceseessnneeeeeeeeeseeeees 67 2 7 11 2 Winch that Changes Cable Length sii ieusasacdessidspessictucdehuneiocevennas voldpbadenvesbusCoseerunaeduenarss 68 2 7 1 2 Cable Fall UTE areni ee e R E TAAA ieee Seung tad Havant ea teas 69 ZR SOMIIO Mt A E pas ccna aseitets taldit eo paves reach tet payed a abate nea ea a E snow Slane Reb eo oN 69 2 8 1 Hydrostatic Results areena isre EE EEEE KEE EEEE ETE ERE AEO EA EE EES 70 2 8 2 Hydrodynamic Graphical Results ssssesssessesssssessssseessssressssrtessssressssteesssresssereesssetesssseeesssere 71 2 8 2 1 Hydrodynamic Diffraction Results ssesssessssssssesssssressssressssreessssresssseesssetesssereesssseesssee 74 2 8 2 1 1 Diffraction Froude Krylov Diffraction Froude Krylov Linearized Morison Drag and Total Exciting Force Including Morison Drag sssccceesssseeceessnceeeeessaceeeessaeeseesneeeees 74 2 8 2 1 2 Response Amplitude Operators RAOs and
28. amp Shin Reference Haight om Speed Oms Direction of For a User Defined spectrum in addition to the Reference Height Speed and Direction you need to enter the following in the Details panel Frequency Coefficient Speed Coefficient surface drag coefficient or roughness I z turbulence intensity In the Data panel you need to enter in each row of the table a dimensionless frequency f and its asso ciated spectral ordinate U f For user defined spectra the dimensionless frequency is defined as f cf 7 Uz F where F is the frequency in hertz The wind speed spectral density is defined as S F cs U f I z Uz 2 F Only 25 rows may be entered Activity Not Suppressed Wind Spectral Definition Spectra User Defined Reference Height Om Speed O mis Direction o Frequency Coeffeciert 1 Speed Coeffecient 1 I z 0 167 The following wind spectra are described in more detail 2 7 10 1 Ochi and Shin Spectrum 2 7 10 2 API Standard Spectrum 2 7 10 3 NPD Standard Spectrum 2 7 10 4 ISO Standard Spectrum 2 7 10 5 User Defined Spectrum 2 7 10 6 Time Dependent Velocity Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 59 Approach 2 7 10 1 Ochi and Shin Spectrum The ordinate of this wind spectrum is calculated from the paper by M K Ochi and Y S Shin OTC 5736 1988 to which the user should refer f
29. and possibly to set inflation parameters that differ from the global ones as there could be more than one of these controls set for a given geometry If Use Inflation is set to Yes without one of these controls being present an error message is issued and the cell is yellowed Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 38 of ANSYS Inc and its subsidiaries and affiliates Establish Analysis Settings 2 5 2 4 Defeaturing Aqwa allows you to control the creation of the mesh in difficult areas of the geometry as described in Defeaturing Group in the Meshing User s Guide In order to use Pinching a Mesh Local Pinching Control object must be created If Use Pinching is set to Yes without one of these controls being present an error message is issued and the cell is yellowed 2 5 2 5 Generated Mesh Information This section shows the number of nodes and elements diffracting and non diffracting in the mesh 2 5 3 Local Mesh Controls 2 5 3 1 Sizing Control Adding a Mesh Sizing object enables the refinement of a mesh on a given part or body by enabling a smaller element size to be associated to the geometry Local Element Size can be set once you pick a body on the geometry using Select Geometry Any number of sizing objects can be added to the tree as required 2 5 3 2 Pinching Control Adding a Mesh Local Pinching Control object allows you to remove small features in
30. following information in the Details panel Type To add a joint select the type of joint you are adding Note In the following images the joints are shown with their two ends split apart Each end is attached to one of the two joint structures or a structure and a fixed connection point Each end of the joint has a set of axes attached to it that corresponds to its position with respect to the structure that it is attached to The curved colored arrows in the figures Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 30 of ANSYS Inc and its subsidiaries and affiliates Define Connections below indicate how the two ends will be connected When the two sets of axes are coin cident the starting position of the structures in the simulation may be different from that in the imported geometry Ball and Socket Free to rotate about all axes Figure 2 1 Ball and Socket Joint Universal Free to rotate about two axes transmitting a moment about the third axis at right angles to the first two Figure 2 2 Universal Joint Hinged Transmitting a moment about two axes and free to rotate about the third axis at right angles the first two Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 31 Approach Figure 2 3 Hinged Joint Rotation is a
31. for forces or RX RY or RZ for moments The required Direction can be chosen e The required Frequency offset can be chosen e When Force Moment plots are performed the SubType field is shown to enable the selection of the full Amplitude component or just the Real or Imaginary components Line Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the first Frequency or Direction at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Surface Graph Input e Use the Component input to select which force component to plot either X Y Z for forces or RX RY RZ for moments The required Direction can be chosen e When Force Moment plots are performed the SubType field is shown to enable the selection of the full Amplitude component or just the Real or Imaginary components Surface Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the Frequency and Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 1 6 Splitting Forces Result Description 2D or 3D graphs to illustrate how the Splitting Forces vary with frequency direction or both frequency and direction Plot availability Line graph presentation Force Moment vs Frequency or Direction e Lin
32. in general should be within the range of that in the Hydrodynamic Diffraction analysis Note Both Frequency and Period are enabled as parameters but in practice you would only choose one of these two to be parameterized as Period 1 Frequency If you were to parameterize both and then enter values from the Project Page that don t conform to this relationship only one of the values will be used and the other ignored The wave ramp is introduced to reduce the transient motion of the structure at the beginning of a time domain analysis The wave ramp will take effect from t 0 0 to t tw during which time a wave ramp factor f 0 0 lt f lt 1 0 will be calculated and then used to multiply the incident wave amplitude The wave ramp factor f is f sn Z w Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 49 Approach It can be seen that at t 0 the factor is 0 0 and at t t the factor is 1 0 If Ramping Method is set to Program Controlled ty will default to the wave period For Defined Ramping Set the Ramping Factor to the desired time tw 2 7 7 Irregular Wave Details of Irregular Wave 1 Name Irregular Wave 1 Visibility Visible Activity Not Suppressed Wave Range Defined by Frequency Wave Spectrum Details Wave Type Pierson Moskowttz Direction of Spectrum 10 Seed Definition Program C
33. in the tree Note If you are running on Windows 7 you must be using a Basic Theme for your desktop in order to capture an image If you are using an Aero Theme a warning dialog box will appear when inserting the Image or Image to File objects and the image will not be properly created 4 3 3 Figures The Figure object allows you to capture a graphic displayed for a particular object in the Geometry window A Figure object can be further manipulated rotated for example unlike an Image object which is a static screen shot of the current model view or an imported static figure You can insert a Figure object in the tree by clicking on the New Figure or Image button in the toolbar From the drop down menu select Figure Figure 4 4 New Figure or Image Menu ai e Figure 9 Image Image from File 6 Image to File Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 99 Common Features In the Details view you can enter a Name for the Figure object Figures will appear in a generated Report under the parent object in the tree Figures allow you to capture result contours mesh previews graphs etc for later display in the Report Any object that displays 3D graphics may contain figures View settings maintained by a figure include camera settings e result toolbar settings e legend configur
34. joints is different on both structures In some cases it is recommended that you use a single joint of a different type that will perform the same function as two simpler joints For example two ball and socket joints could be replaced by a single hinged joint or two hinged joints could be replaced by a rigid joint A closed loop should not result in any redundancy in the way that the degrees of freedom will be locked For example if three articulated structures are connected to form a triangle and two of the joints are of the hinged type with the same orientation for the hinged axis the third one should be a ball and socket joint because making it a hinged joint would be redundant The two other hinged joints already prevent one of the rotations for this joint Figure 2 5 A Working Closed Loop Mettipte Systems Hydrodynamic Time Response ANSYS AQWA HYDRO DIFFRAC Fle Edt Vem uis He id S 3 A S St QQaHQatnm SOON Coradia GP tort Jre Cades ft Conecton Stines g E Project a Model 83 C3 RD Gecentry ooo Outs Tas Warning ort Jort Y is gestina o loop whid may couse errors while siina Please refer to document on Info COMPLETED SUCCESSFULLY Info NEGATIVE DAMPING DETECTED STRAI MOCE PRETDOME AT PRECUENCY o 12 rfo NEGATIVE DAMPING DETECTED STRAI MODE PREEDOME AT FREQUENCY lt 0 12 rfo NEGATIVE DAMPING DETECTED STRA MODE PREEDONE2 AT FREQUENCY lt 0 12 info NEGATIVE DAMPING DETECTED S
35. maximum value of wu is 0 5 Size The fender size e Polynomial Coefficient A B C D E The force acting on the structure is Ax Bx Cx Dx4 Ex where x is the compression applied to the fender Fender friction works best in situations where the friction force is smaller than other forces in the same direction Friction will slow down relative motion between two structures but is not suitable for keeping them fixed together there is no stiction When the relative velocity changes sign the friction force must also change sign but to avoid an instantaneous change in force and therefore an instantaneous change in acceleration a smoothing function is applied This means that when the relative velocity is very small the friction force is also small and the structures can move relative to each other Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 27 Approach When inserting a fender Fender Axes and Contact Axes objects are inserted as its children These axes objects define the orientation of the fender and the contact plane The orientation can be set using these fields in the Details panel for each axes object Alignment Method Select Global Axes to align the axes with the global axes You can also set the alignment of the axes using the Vertex Selection or Direction Entry methods Origin Vertex X Direc
36. of 41 directions for any one structure Note It is not possible to employ symmetry in Aqwa 2 7 4 Wave Frequencies The Wave Frequencies tree object enables the definition of a range or single wave frequency to use in the analysis By default the frequency Range is Program Controlled this equally spaces the specified Total Number of Frequencies between a minimum value based on the water depth and a maximum based on the mesh size The spacing interval can either be based on constant frequency or constant period increments Equal Intervals Based Upon Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 47 Approach You can manually define one or more single frequencies or range of frequencies by selecting Manual Definition for the Range For a single frequency set Definition Type to Single Enter the Lowest Fre quency or Longest Period To specify a range of frequencies set Definition Type to Range Enter a Lowest Frequency and Highest Frequency or a Longest Period and Shortest Period The start frequency will default to 0 1 rad s and the end frequency will default to that determined by the mesh The maximum wave period and equivalent frequency permitted is 200s The intermediate positions can be defined either by a constant frequency or period or by entering a number of values Set Interval Type to Frequency or
37. of the surface body will be obtained from that given in Design Modeler and it cannot be changed here If a body is not required for the analysis it can be suppressed Body Activity Suppressed bodies will not be meshed and will be excluded from the analysis You can hide the body in the graphic window Body Visibility in which case it will not be shown but will be included in the analysis Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 10 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior It is possible to change the type of surface from a Physical Geometry to an Abstract Geometry Structure Type For physical geometry Program Controlled Surface Type will set all surface bodies below the water surface as diffracting and those above will be non diffracting If required those below the water surface can be manually defined as non diffracting elements for the analysis This may be required for instance when part of the structure is in contact with the sea bed or where contact occurs underwater between adjacent parts For an abstract geometry Abstract Type provides a number of options to select how this geometry is to be used If an area is of particular interest then the Custom Results Positions option enables a mesh to be applied and each node of the mesh will form a field point element additional information will be available at these points Alternativ
38. option may be used to input any user defined spectrum It is normally employed for input of non deterministic spectra such as tank spectra recorded full scale spectra or simply where the formulated spectrum is not yet available In the User Wave Spectrum Definition Data table enter the frequency or period depending on the Wave Range Defined by setting and its corresponding spectral ordinate The maximum number of frequencies periods is 50 User Wave Spectrum Definition 9 E Details of Irregular Wave Frequency Hz Spectral Ordinate Name Irregular Wave Visibility Visible Activity Not Suppressed Wave Range Defined by Frequency Wave Spectra Details Wave Type User Spectra 1D lO Direction of Spectrum 0 Seed li Cross Swell Details Cross Swell Spectrum None Length units mm h 2 7 7 5 User Time History A time history series of wave elevations may be imported into your Hydrodynamic Time Response analysis in order to reproduce model test wave conditions as accurately as possible Select Insert gt Ir regular Wave gt Import WHT File or select Irregular Wave gt Import WHT File from the Analysis toolbar and browse to the file location Note After the data is imported no record of the file used to import the data is retained When drift effects are included in the analysis the wave elevation time history will be reproduced exactly within
39. steel wire mooring line Tension in a steel wire mooring line is given by T k e d tanh e d Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 21 Approach Where e extension of mooring line k asymptotic stiffness constant d asymptotic offset constant The names of the constants k and d arise from the fact that at large values of extension tanh e d tends to unity and the equation tends to the asymptotic form T k e d 2 4 1 4 Non Linear Catenary Non Linear Catenary Cables consist of up to 10 Catenary Sections and optionally 9 Catenary Joints between the sections Catenary Sections and Joints can be defined under the Catenary Data object and accessed as required to build up a number of Non Linear Catenary Cables For each cable the Section Type field allows you to select the Catenary Section via a drop down list once chosen the unstretched Length of that section can be entered If more than one section is used then additional selections for the joint type are displayed to allow the selection of the Catenary Joint The whole cable make up is summarized in the Catenary Cable Definition Data table Each Non Linear Catenary Cable can optionally be analyzed using cable dynamics to obtain the dynamic forces in the cable as well as their effect on the structures motion Set Use Dynamics to Program Control
40. stretched line speed for paying out then the speed specified should be input with a reduction factor of 1 1 e 2 where e is the average strain To set up the changing cable length Cable Winch object click on the object In the Details panel Select Changes Cable Length from the Cable Type dropdown list Select the cable to associate with the winch from the Cable Selection dropdown Enter the value of the Start Time Enter the cable s Final Length at which winching will stop Enter the value of the Speed of the winch Enter the Max Tension at which winching will pause Enter the Additional Length which affects the initial stiffness of the cable Note The exact length of the line at any time will depend on the previous motions which have been encountered by the structure connected to this line This in turn means that the length of the line has memory The implication of this is that in situations where initial or specific positions are used in Aqwa the line length cannot be determined and will be assumed to be the initial Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 68 of ANSYS Inc and its subsidiaries and affiliates Solution length An example of this is the hot start A warning message to this effect will be issued in these cases The resolution of switching on and off the drum winch can only be the same as the time step This means that the w
41. subtypes of the Structure Acceleration during the analysis Actual Response Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 82 of ANSYS Inc and its subsidiaries and affiliates Solution Low Frequency The low frequency subtype values are obtained by filtering the actual response with a filter which has a cut off frequency of one third of the frequency of the 10 spectral line i e with N spectral lines n 0 1N 1 Wcutoff Wn 3 Wave Frequency the wave frequency response is that which remains when the low frequency re sponse is subtracted from the actual response RAO Based The RAO based motions are those that are calculated using only the RAOs ignoring the affects of connections unless these are included as additional matrices in the diffraction analysis using the applied wave These values are calculated at the center of gravity and are available in all translational and rotational component directions Plot availability Line graph presentation Acceleration plotted against Time Line Graph Input Use the Component input to select which Acceleration component to plot either X Y or Z for transla tional acceleration or RX RY or RZ for rotational acceleration Line Graph Output Maximum Value and Minimum Value of Structure Acceleration and the Time at which they occur Position of Min in X Position of Max in X These values can be param
42. the lowest anticipated database point to the connection point in the definition position and Positive dZ measured from the connection point in the definition position to the highest anticipated database point along with the slack and maximum tension positions including the effects of the Sea Bed Slope This area is then divided up to form a database of cable end positions and corresponding tensions which is used in the analysis It is recommended that the full size of this grid is used of 600 points which is formed by the multiplication of Number of Vertical Partitions and Number of X Coordinates Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 22 of ANSYS Inc and its subsidiaries and affiliates Define Connections Vertical range determined by Positive dZ and Negative dZ above and below the vertex position divided into the number of Vertical Horizontal range determined by maximum tension and slack position divided into the number of X coordinates Partitions Seabed slope affects slack position For cables attached between two structures Connectivity set to Structure amp Structure the range of the possible end points of the cable is determined by the relative positions of the two structures along with the slack and maximum tension range It is assumed that the cable does not contact the sea bed It is recommended that the full size of the database is
43. the diffraction defined position To add an Additional Hydrodynamic Stiffness Matrix 1 Select a part in the Tree Outline 2 Right click on the part and select Add gt Additional Hydrodynamic Stiffness or Click on the Add icon in the toolbar and select Additional Hydrodynamic Stiffness from the dropdown list An Additional Hydrodynamic Stiffness object is added to the part Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 13 Approach 3 Select the Additional Hydrodynamic Stiffness object in the Tree Outline and enter the matrix coefficients in the Matrix Definition Data window that appears below the model 2 3 7 Additional Damping Frequency Independent This object may be used to input frequency independent additional damping in global directions using tabular input Only one definition of Additional Damping per structure can be active i e not suppressed for the analysis and the values are added to those calculated automatically during the analysis To add Additional Damping 1 Select a part in the Tree Outline 2 Right click on the part and select Add gt Additional Damping or Click on the Add icon in the toolbar and select Additional Damping from the dropdown list An Additional Damping object is added to the part 3 Select the Additional Damping object in the Tree Outline and enter the matrix coefficie
44. 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 16 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior An error will be reported if there are multiple entries having the same value of Direction in the table 2 3 10 Wind Force Coefficients This object may be used to include the viscous drag of the wind on the superstructure of a fixed or floating structure using tabular input in the Wind Force Coefficients window The term wind force coefficient is used to differentiate these coefficients from traditional drag coefficients and from coefficients of current force The wind force coefficients are defined as the force or moment per unit velocity squared The moment is about the center of gravity of the structure These forces are a function of the relative velocity between the structure and the air This means that the wind coefficient should still be input even when there is no wind present as the relative velocity is generally non zero for a dynamic analysis To add a Wind Force Coefficients object 1 Select a part in the Tree Outline 2 Right click on the part and select Add gt Wind Force Coefficients or Click on the Add icon in the toolbar and select Wind Force Coefficients from the dropdown list A Wind Force Coefficients object is added to the part 3 Select the Wind Force Coefficients object in the Tree Outline and enter the coefficients in the Wind Forc
45. 3 1 Hydrodynamic Context Menu Options in the Project Schematic Be Hydrodynamic Diffraction Geometry i New Geometry Model 3 4 R2 Setup 5 6 n Import Geometry Duplicate Ws Solution B Results Hydrodynamic Diffraction Transfer Data From New ogi ogi ogg agh Transfer Data To New Update Reset Rename Properties Quick Help Please refer to Context Menu Options for more information on all of the available options such as Du plicate Update Refresh Clear Generated Data Reset Rename Properties and Quick Help 3 2 The Aqwa Editor User Interface Hydrodynamic analysis systems open a Workbench based editor that is a graphical interface for Aqwa analyses Using this editor you can create an element based model from geometry defined in Design Modeler format apply Aqwa specific input and view results The layout is similar to other Workbench based applications e g the Mechanical application and comprises a number of objects in a tree based layout Hydrodynamic analysis systems follow the conventions used in other ANSYS Workbench products where it is appropriate for the Aqwa Editor The user interface has a number of key areas but is tree driven Along with the tree and its details pane are toolbars and graphical text display windows The toolbar uses a number of standard Workbench icons along with a number of specialist additions Table 3 1 Standard Workbench Toolbars
46. 4 A n The Longitudinal Drag Coefficient Cx Inline drag force is calculated by 0 5 p Cx V2 De per unit length where V is the relative inline velocity The default is 0 025 2 4 2 2 Catenary Joint You can insert either a buoy or a clump weight between catenary cable sections however you do not need to specify a joint Intermediate buoys always have the same buoyancy and do not know where the surface is Therefore they may float above the water surface To define the properties of a catenary joint right click on the Catenary Data item in the tree and select Insert Catenary Data gt Catenary Buoy or Insert Catenary Data gt Catenary Clump Weight Click on the Catenary Joint object that you added and enter the following information in the Details panel Section Joint Type should be set to Buoy or Clump Weight based on your menu selection when adding the object Specify the Structural Mass of the buoy or clump weight This must be smaller than the mass of displaced water for a buoy or larger for a clump weight This can be positive zero or negative Specify the mass of water displaced Displaced Mass of Water i e the buoyancy gravity This can be positive zero or negative Specify the total constant Added Mass i e not the added mass coefficient Applicable to Cable Dynamics only Specify the Drag Coefficient Area cable dynamics only drag will be in the direction of the relative velocity of the fluid VR The magnitude o
47. 5 m MT 6 020604 m MZ 1495807 m AM Wan Preannom a om as Cut Water Plane Properties s me Oat Water Plane Arex A ttydodynama Tene Response 2 C4 Centre of Fioatason A hress anmas Principal Jed Moment of Area fits ad Angie Principal Axis makes with X FRA owe O soten cs Small Asgle Stability Parameters COG wCOBGG Metacentk Heights GMX GMY 1 70065 m s 3 COB to Metacentre BMX BMY 8 02222 m hd Restoring Moments Degree Rotations Cet ads of Itpdrest ata OXMY 1636 N m 6 045808 N m e ro we arte PI raphe sl Represent stion Dow Cortes of Ga ton row Contre of Du tes Show Contre of Pio Yes euas Actual Ongieced 6055156 m Metante hee S OSOREZT a aA of bore Olest OO Pree Pa for Help Length unts Note For best graphical display of hydrostatic results it is recommended that you change the View options to enable Wireframe and turn off Select Tree Related Items 2 8 2 Hydrodynamic Graphical Results The Hydrodynamic Graphs button on the Insert Results toolbar allows you to plot your results using either a line surface or contour surface plot When you select a graphical object in the tree the graph will be displayed in a Graph tab in the main window pane and the data for the graph will be displayed in the window pane below the graph There are a number of different types of graphs that can be displayed and a number of different axes combinations that can be displayed 2D lin
48. AOs Only If Yes calculates motions using RAOs only Note that this option suppresses all motion except that defined by the RAOs In particular current wind drift forces moorings etc have no effect on the motions of the structure Call Routine user_force If Yes calls a routine called user_force at each stage of the calculation This routine can be used to add externally calculated forces to the simulation Convolution If Yes specifies that convolution method is used in radiation force calculation This is a more rigorous approach to the radiation force calculation in time domain and will enhance the capability of handling nonlinear response of structures Ignore modeling rule violations If Yes continue the analysis in spite of the modeling rule violations Most of the modeling errors will be turned into warnings by this option Do not use this option unless the violations are minor and difficult to correct Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 43 Approach Linearized Morison Drag If Yes computes linearized Morison drag for TUBE DISC and STUB elements In order for the drag to be computed after enabling Linearized Morison Drag an Irregular Wave must be added to the Hydrodynamic Diffraction analysis Only one spectrum can be defined no Irregular Wave Group The Irregular Wave must have only a single d
49. Bise QQamMag insert Resut M Hydrostatic T Mydrodynamc Graphs Pressures and Motions E Force Moment vs Frequency Shear Force or Bending Moment Z Component Only gt Force Moment vs Frequency Frequency Shear Force or Bending Moment Al Components gt i Phase vs Frequency E Phase vs Frequency Frequency A Hydrodynamic Graph K Hydrodynamic Graph When you select a Hydrodynamic Graph result object under Solution the graph will display in the Graph tab of the upper right pane of the window and the data for the graph will display in the pane below the graph Various fields will appear in the Details panel depending on the type of graph and the axes that are displayed If the input to an analysis is changed then the results objects will indicate that they are out of date via the yellow lightening bolt icon however if previous results exist they will still be available until the analysis is re run Changing the Axes Selection for any graph will cause that result object to require an update which can be done from the right click menu The following types of results are available 2 8 1 Hydrostatic Results 2 8 2 Hydrodynamic Graphical Results 2 8 3 Hydrodynamic Pressures and Motions Results 2 8 4 Time History Motion Results 2 8 1 Hydrostatic Results The Hydrostatic results tree item enables you to view the centers of buoyancy flotation and gravity in the graphical view once a hydrostatic or hydrodynamic sol
50. Combined Meshing is used if the part also includes lines If the Program Controlled option fails to produce a satisfactory mesh then you may control the selection manually The larger the maximum element size the less accurate the results The 32 bit version of the Aqwa solver is limited to 18000 elements of which 12000 may be diffracting The 64 bit version of the Aqwa solver is limited to 40000 elements of which 30000 may be diffracting The number of generated elements Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 37 Approach is reported although these exclude any non meshed elements e g Discs and elements that may be created automatically if an internal lid is specified Furthermore if the size is set too large and defeaturing is also large the meshing algorithm may gen erate single elements at the bow of a ship This element arrangement is not permitted for Aqwa 2 5 2 Advanced Global Mesh Options If Global Control is set to Advanced extended meshing options are available in the Details panel These options are organized into the following groups 2 5 2 1 Mesh Parameters 2 5 2 2 Sizing 2 5 2 3 Inflation 2 5 2 4 Defeaturing 2 5 2 5 Generated Mesh Information Note The sections that discuss the advanced meshing options refer you to the Workbench Meshing User s Guide Generally the Aqwa Mesh objec
51. Damping If Yes suppresses the calculation of wave drift damping for yaw motion To prevent the calculation of all wave drift damping use the No Automatic Wave Drift Damping Calculation option Tube Drag Coefficients If set to Defined in Geometry uses the Viscous Drag Coefficient fields of the Line Body objects in the Geometry If set to Reynolds Number Dependent causes drag coefficients to be calculated using the Wieselburger graph of drag coefficient versus Reynolds Number Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 44 of ANSYS Inc and its subsidiaries and affiliates Establish Analysis Settings Drag Coefficients versus Reynolds Numbers for Circular Cylinder Scale Factor for Model Test Simulation Only available if Tube Drag Coefficients is set to Reynolds Number Dependent Set to unity default to provide simple Reynolds Number dependent drag calculations using the Wieselburger curve If com parisons against scaled model tests are to be undertaken then provide the scale factor of the model here For example if the scaled model is 10 1 then specify a factor of 10 The scale factor is used as follows Local Reynolds Number UD v Scale Factor where U Local velocity transverse to the axis of the TUBE D The diameter of the TUBE v Kinematic viscosity of water Use Linear Starting Conditions If Yes starts a simulation with the motions and velociti
52. Frequency Dependent Parameters and Stiffness Matrix Parts Structures Additional Stiffness Additional Damping Additional Added Mass Connection Stiffness 4 8 DECK 8 DRC Drift Force Coefficients Not Supported 4 9 DECK 9 DRM Drift Motion Parameters 4 10 DECK 10 HLD Hull Drag Coefficients and Thruster Forces Not Supported Current Force Coefficients Wind Force Coefficients 4 11 DECK 11 ENVR Environmental Parameters Wind non spectral definition Current Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 104 of ANSYS Inc and its subsidiaries and affiliates Transferring Pressures and Motions Frequency Domain to Mechanical Models Aqwa Manual Reference Aqwa Editor Tree Object 4 12 DECK 12 CONS Constraints Not Supported 4 13 Deck 13 SPEC Spectral Parameters Irregular Wave Wind spectral defini tion 4 13N Deck 13 WAVE Regular Wave Parameters Regular Wave 4 14 Deck 14 MOOR Mooring Lines Description Cables Cable Winch Cable Failure Analysis Settings 4 15 Deck 15 STRT Starting Conditions Not Supported 4 15N Deck 15 STRT Starting Conditions NAUT Not Supported 4 15D Deck 15 STRT Starting Conditions DRIFT Not Supported 4 16 Deck 16 STRT Starting Conditions Not Supported 4 16L Deck 16 STRT Starting Conditions LINE Not Supported 4 16B Deck 16 STRT
53. NEGATIVE DAPPING DETECTED STAA 1 MODE PREEDOME AT PRECLENCY 0 12 Into NEGATIG DAMPING DETECTED STAA MOCEITEET DOM AT FEDOLENCY 0 12 em 7 Largh unas m Figure 2 6 A Failed Closed Loop p 36 shows a failed closed loop joining three wireframe structures The ball and socket joint from Figure 2 5 A Working Closed Loop p 35 has been replaced by a third hinged joint Removing the ball and socket joint has added a useless constraint to the problem Since all three joints now have limited motion there is redundancy in the way the degrees of freedom are locked When you close a loop you will get a warning message informing you that a loop is being closed and that this may cause errors while solving If you are experiencing solver failures when working with closed loops and have followed the rules defined here please contact the support team for assistance 2 4 5 4 Removing a Joint Joints can be removed from an analysis temporarily or permanently by right clicking on the Joint item in the tree and selecting Supress or Delete The result is that the group of articulated structures that contains the joint is broken into two parts Closed loops that are suppressed or deleted are opened If the starting positions of some structures were modified when the joint was created they will be moved again using the following rules If the two structures are not part of any group they will be returned to the positions they held w
54. Period and use No of Intermediate Values or Interval Frequency to specify intermediate positions If a number of intermediate values are chosen they will be equally spaced depending upon the interval type To specify additional frequencies set Additional Range to Single or Range and enter the Period Fre quency and Interval information Any duplicate frequencies will be automatically removed The number of frequencies chosen extends the solution time linearly Note If a mesh size is modified after the creation of the frequency object the maximum frequency is not altered and may need to be updated manually 2 7 5 Structure Force A time history of structure forces applied at the center of gravity can be defined directly in a table or by importing the data from an existing XFT file To define the data directly in the table right click on the Hydrodynamic Time Response object and select Insert gt Structure Force gt Manual Input To read the data from a file select Insert gt Structure Force gt Import XFT File and browse to the file location You can also insert the object by clicking Structure Force on the Analysis toolbar and selecting one of the options Note After the data is imported no record of the file used to import the data is retained In the Details panel the column definition can be associated to the appropriate structures in the model A row has to be filled in for all structures additional rows can b
55. Point Mass is defined either manually by the user or automatically by the program after the hydrostatic calculation has been done and is up to date If the hydrodynamic diffraction system is not up to date this information is solely based on the initial 1kg mass attributed to each point mass if its definition is Program Controlled or on any subsequent out of date hydrostatic analysis If an internal lid is required to prevent irregular frequency problems then Generate Internal Lid can be set to Yes and it will be automatically generated during the Aqwa analysis Note that an automatically generated lid will not be displayed Alternatively a manually generated lid may be used create an ap propriate plane surface as a Surface Body set Structure Type to Abstract Geometry and Abstract Type to Internal Lid If you have a structure with a moon pool where large resonant waves may occur then you can form an external lid using a predefined geometry Surface Body with Structure Type set to Abstract Geometry and Abstract Type to External Lid The Current Calculation Depth defines the depth below the water surface at which the current velocity is to be computed for use in the calculation of the hull drag loading By default the current at the water surface is used Note that hull drag loads are only included if Current Force Coefficients are defined for the part By default the structure is set to be free to move Alternatively the whole structure can be
56. System for more information Note In hydrodynamic analysis systems the Geometry cell is the only cell that can share data with other types of analysis systems 2 2 Attach Geometry There are no geometry creation tools in the Aqwa application so geometry must be attached to the hydrodynamic system You can create the geometry from either of the following sources From within Workbench using DesignModeler See the DesignModeler Help for details on the use of the various creation tools available From a CAD system supported by Workbench See the CAD Integration section for a complete list of the supported systems Before attaching the geometry from either of these sources you can specify several options that de termine the characteristics of the geometry you choose to import by right clicking on the Geometry cell and choosing Properties See the CAD Integration section for more details about the options most of which do not apply in hydrodynamic analyses Also see the General Modeling Requirements section for more information about the implications of Geometry import properties Note Aqwa only processes the Line Bodies and Surface Bodies in a geometry Make sure that the boxes are checked for both of these Geometry options in the Properties view You can attach a geometry that has no line or surface bodies but Aqwa will not process the geometry Related Procedures Procedure Condition Procedural Steps Specifyi
57. TAA MODE FLEEDOM s AT FREQUENCY 12 info NEGATIVE DAMPING DETECTED STR21 MODEJFREEDOME 2 AT FREQUENCY 12 lt Nessanes AT on Figure 2 5 A Working Closed Loop p 35 shows a working closed loop consisting of two hinged joints and one ball and socket joint In this view the structures that are being joined have been changed to wireframe images to allow the joints to be seen more clearly The two hinges lock the relative roll and pitch for all three structures This means that the third joint must have the full range of movement of a ball and socket joint in order to prevent redundancy Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 35 Approach Figure 2 6 A Failed Closed Loop of Sructre Seain oh Weve Deeds ah Weve Frequences AL Sebetion 85 A Hydrodynamic Time Response 2 C4 IN iness Settings A regis wave C Setetion C5 botats Detet of Setetion ow Satin hgoometry An A Arot Proview Error Solve aborted Eno TERMINATED WITH ERRORS Erre SOLVES PRITPAL MINORS ARE NOT NON ZERO TRIAMGULISATION ABANDONED UNEJ Into NEGATIVE DAYEING DETECTED STR S MOCE PELEDOME AT PREOLENCY 0 12 irto NEGATIVE DAMPING DETECTED RSI MOOEIFREEDOME AT FRE WY Info NEGATING DAMPING DETECTED STRAZ MODE PEEEDOMS AT PPD NCY irto NEGATIVE DAYPING DETECTED STAA MODE FREEDOME AT FRE 2 Info
58. Uz and S F Wind speed energy density S f Non dimensional wind spectrum s z Wind speed standard deviation F Frequency in hertz z Elevation Uz Wind speed at elevation z cf Frequency coefficient Note that the frequency coefficient cf is associated with the length scale in some formulations It is not used in others in other words cf is unity A single user defined wind spectrum U f is input by the user in non dimensional form The maximum number of frequencies periods is 50 The frequencies at which the spectral ordinates are specified are non dimensional The user defined spectral energy density is therefore fully defined by the following user input parameters Uz the mean wind speed default 0 0 z the reference elevation NO DEFAULT cf Frequency coefficient default 1 0 cs Spectrum coefficient default 1 0 I z turbulence intensity default 1 6th f U f for each frequency where s z I z Uz S f cs U f Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 63 Approach We note that in some form of wind spectra cs is associated with the surface drag coefficient or roughness Ochi and Shin Harris DNV Davenport etc while other spectra for example API do not use this coefficient in other words cs is unity The z reference elevation is used to calculate the non dime
59. al Movement or Upward Z Movement Line Graph Output Maximum Value and Minimum Value of the Fender Force and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box 2 8 2 2 6 Joint Forces Result Description 2D graphs to illustrate the joint forces during the analysis You must select the Structure and Connection to that structure connected Joint for which you want to display the results Plot availability Line graph presentation Force Moment plotted against Time Line Graph Input Use the Component input to select which Joint Force component to plot either X Y or Z force com ponents or RX RY or RZ rotational components Line Graph Output Maximum Value and Minimum Value of the Joint Force and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box 2 8 2 2 7 Cable Forces The force components are available for each cable For catenary cables sections section tension is also available Result Description 2D graphs to illustrate cable tension during the analysis e Whole Cable Forces Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 85 Approach Cable Section Tension Plot availability Line graph presentation F
60. and a vertex that would along with the other two vertices define the XY Plane Vertex Defining the XY Plane Rotation about Global Z Rotation about Local Y Rotation about Local X For an Alignment Method of Direction Entry define the alignment using these three rotation fields Note If your joint is connecting the structure to a fixed connection point it will be indicated by a black sphere This black sphere is not to be confused with the sphere of a ball and socket joint 2 4 5 1 Initial Positioning of Jointed Structures In hydrodynamic analyses inserting joints between two structures affects the initial position of these structures when the analysis is run Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 33 Approach The program automatically determines the initial positions based on the defined joints so that you do not have to edit the model s initial geometry If two connection points are not coincident the program moves one of the structures to align the connection points before running the analysis The geometry movement will not be shown in the viewer You can control which structure will remain in a defined position and which structure is free to move by selecting Connection Point on Structure A or Connection Point on Structure B in the details dialog for the joint Fixed connections are shown in b
61. and force applied depend on the Connectivity defined the following information is not applicable to catenary cables For a cable attached between a structure and a fixed point The extension of the cable at any stage of the analysis is calculated by subtracting the unstretched length from the distance between the position of the fixed point and the current position of the con nection point on the structure The direction of this force is given by the vector going from the fixed point to the structure For a cable attached between two structures The extension at any stage of the analysis is calculated by subtracting the unstretched length from the distance between the connection points on the two structures at the current position of the respective structures The direction of the force on a structure is given by the vector going between the two connection points The forces on each structure will therefore always be equal and opposite and hence the selection of start and end connection points can be interchanged The unstretched length is used to indicate the length at which the mooring line is slack i e if the distance between the two attachment points at either end of the mooring line is less than this value then the tension in the mooring line will be zero Although unusual it is quite valid to input this value as zero where the cable is never slack However in the special case where both ends of the cable are coincident the dire
62. anslating the original definition point down to the mean water surface following this plane It therefore models the ship s side which is not necessarily vertical Omnidirectional fixed fenders act in all directions Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 26 of ANSYS Inc and its subsidiaries and affiliates Define Connections The size of the fender must be specified At each time step the distance between the fender s attachment and the contact plane is calculated and compared to the fender s size If the distance is shorter than the size a force is calculated as a function of the difference following a polynomial law whose coefficients are part of the fender s definition This force is applied to the structure at the fender s attachment point The calculation of the distance depends on the type of fenders Fixed unidirectional and floating fenders have a direction along which the distance is calculated For the omnidirectional fender the distance is simply the shortest distance from the contact plane to the attachment point Fenders can only have compressive forces To add a fender to your analysis right click on the Connections tree object and select Insert Connection gt Fender or click on the Connections object and select Fender from the Connections toolbar You will need to enter the following information in the Details panel Connectivity Select the type of c
63. ant to save the file Click Save Note If you are running on the Windows 7 operating system you must be using a Basic Theme for your desktop in order to export an animation If you are using an Aero Theme a warning dialog box will appear when you start the export and the exported video file will not be properly created When entering time into the animation toolbar fields you must press the Enter key before leaving the field in order to set the value The animation must be stopped in order to export a video If you try to export a video while the animation is playing on the screen nothing will happen Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 90 of ANSYS Inc and its subsidiaries and affiliates Chapter 3 Aqwa Workbench Interface Hydrodynamic analysis systems are available to place on the Workbench Project Schematic from the Toolbox After configuring the connections to from the Hydrodynamic analysis systems and or any inputs to the systems you will open the Aqwa Editor to perform the analysis and view the results of the Hy drodynamic analysis system This chapter discusses how to place and configure your analysis system on the Project Schematic and describes the User Interface of the Aqwa Editor The topics covered are Using the Aqwa Editor User Interface e Setting Aqwa options 3 1 Hydrodynamic Systems in the Project Schematic Hydrodynamic syste
64. ase 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 74 of ANSYS Inc and its subsidiaries and affiliates Solution Plot availability Line graph presentation Phase Angle plotted against either Direction or Frequency Line graph presentation Force Moment plotted against either Direction or Frequency Surface graph presentation Phase Angle plotted against Direction Frequency Surface graph presentation Force Moment plotted against Direction Frequency The Frequency Scale can be modified to be Period Scale if required Line Graph Input e Use the Component input to select which force component to plot either X Y Z for forces or RX RY RZ for moments e When the plot is performed against Direction then the required frequency can be chosen using the Fre quency input e When the plot is performed against Frequency then the required direction can be chosen using the Dir ection input Line Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the first Frequency or Direction at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Surface Graph Input Use the Component input to select which force component to plot either X Y Z for forces or RX RY RZ for moments Surface Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the Frequency and
65. ate of change of the added mass tensor with time multiplied by the velocity The resulting coefficient is then multiplied by this factor This may be used for parametric studies where the effects of slamming loads on tube and disc elements are considered important e g simulating tests at model scale This factor has no effect on any other object type in the part Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 8 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior Slamming loads can also be included for stub elements by setting the Slam Factor to a positive non zero value but the magnitude of the factor is immaterial in this case because a value of unity is always employed in the analysis Note The method for computing the slam coefficient requires that the time step used in a time history analysis must be sufficiently small to accurately represent the added mass at each stage of immersion emergence In general this will depend on the geometry of each element and its orientation to the water surface In practice this severe restriction of the size of the time step means that this facility is only used when specifically investigating the effects of slam forces on individual elements during critical stages of the simulation period as the momentum change due to slam forces are normally small and have little effect on the overall motion of the structure
66. ation A figure s view settings are fully independent from the global view settings Figures always display the data of their parent object For example following a geometry Update and Solve a result and its figures display different information but reuse the existing view and graphics options Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 100 of ANSYS Inc and its subsidiaries and affiliates Chapter 5 Aqwa Systems 5 1 Hydrodynamic Diffraction System There are two analysis options for a Hydrodynamic Diffraction analysis either to calculate the Hydrostatics only Aqwa stages 1 and 2 or to calculate the full Hydrodynamic results 5 2 Hydrodynamic Time Response System A Hydrodynamic Time Response system must be connected to an upstream Hydrodynamic Diffraction system The HTR system must share the Geometry Model and Setup cells of the HD system Note When you drop the HTR system on the HD system in the Project Schematic you are given the option of only sharing the Geometry or Geometry and Model cells with the HTR system Do not connect the systems in either way If all three cells are not shared the analysis will not work When a second Hydrodynamic Time Response system is connected to an upstream Hydrodynamic Time Response system the downstream system begins its simulation at the end time step of the upstream system Figure 5 1 Connected Hydrodynamic
67. be suppressed There are limits on the total number of irregular waves you can insert in a group The total number of spectra is 41 an irregular wave of formulated type Pierson Moskowitz JONSWAP counts for 1 or 2 if you add Cross Swell imported wave time history counts for 1 but you can only have a maximum of 5 imported history and user defined counts for 1 as well 2 7 9 Current Current can be modelled to supplement the wave forces being applied to the structure This can either be a simple constant entry or a range of depths velocities and directions Current loading is applied to the hull of a vessel if hull drag coefficients have been provided and will utilize the current at a specified depth Current loading will be applied to tubular beams and stub elements using the velocities at the depth of the element If cable dynamics is used for the definition of a composite catenary cable current loading will also be applied along the length of the cable using the variable current velocity with depth To insert a Current object right click on the Hydrodynamic Time Response object and select Insert gt Current or click on the Hydrodynamic Time Response object and from the Analysis toolbar select Current To enter the current data click on the Current object to open the Current Definition Data table For a constant current make a single entry in the table that defines the current Velocity and Direction and provide any Depth val
68. ble fails After given time if tension at Cable Start is exceeded enter the analysis Failure Time after which the cable fails if the cable start tension exceeds Failure Tension at Cable Start After given time if tension at Cable End is exceeded enter the analysis Failure Time after which the cable fails if the cable end tension exceeds Failure Tension at Cable End After given time if tension at Cable Start or End is exceeded enter the analysis Failure Time after which the cable fails if the cable start tension exceeds Failure Tension at Cable Start or the cable end tension exceeds Failure Tension at Cable End e If tension at Cable Start is exceeded enter the Failure Tension at Cable Start at which the cable fails e If tension at Cable End is exceeded enter the Failure Tension at Cable End at which the cable fails e If tension at Cable Start or End is exceeded enter the Failure Tension at Cable Start and the Failure Tension at Cable End at which the cable fails 2 8 Solution Results can be added when the Solution object is selected in the tree this can be either before or after an analysis is performed You can add a results object using the Insert Result toolbar or the context right click menu Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 69 Approach Fle Eat ven Um Heb bd Foe Foren HUMB
69. ceeeeceseeensneeeeceeeesseensnaaes 86 284 Time History Motion RES UNS secari e a a a a a i Sead 89 3 Workbench Interface i ea ia caves nol ada eeina Ma aes aai ieii iia a Ee iaie 91 3 1 Hydrodynamic Systems in the Project Schematic cssssccssessnseesessenceseesseceeseeseneeesesseneesonseeseeees 91 3 2 TheAgwa Editor User Interface nioreeosiri gnn o RE OEN RE ON ER O A O 92 3 3 Setting Aqwa Application Options esssssssseeesssssssssereresssssseereresssssssereeeeessssssseeeeesssssseerereeessssesreees 95 4 COMMON Fe t res onrein na a clio Sahar A EEEE er A O EA OA A OAN 97 412 Generating Reports Aera e a a a a a a a e aa o aae 97 AD Parameters oioi n iraa e E EA E EEE EE E EE EE EE a Eaa 97 4 3 Comments Images and Figures sssseesseeeeessssssseereeessssssserteesrssssseereeessssssseereeesssssssereeeesrsssssereeesse 98 ASA E o a OTAI D EE E E E T E EE E EE T E ERT E S 98 me ra anI o EEE E E E E 99 ASS E LO LE E A E T E A E EE S E E 99 S Systems Arii seers EE SERLE EAA E TEA E NAT A EERE E E EEEa 101 5 1 Hydrodynamic Diffraction System ccccesssscccccecceseessnneceeceecesseeesnaeeeeececeeseesnnaaeeeeeeeeseeeesnneeeeeees 101 5 2 Hydrodynamic Time Response System sssessssssesssssessssseesssrressssressssrtessssreessstresssereessereessssressssreesse 101 6 Appendix e eran iena AEE ET EEE E E EE E E E a e 103 6 1 Information for existing AqWa USERS ssssssssessssssesssssrsssssresssereesssreesss
70. ct which force component to plot either X Y or Z for forces or RX RY or RZ for moments Surface Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the Frequency and Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 1 5 Sum QTF and Difference QTF Result Description 2D graphs to illustrate how the QTF results vary with a section taken through the results with a given frequency offset For this result to be valid the frequencies need to be equally spaced 3D graphs to illustrate how these quadratic transfer function QTF matrix which is a force or moment results change with frequency for a given direction Plot availability Line graph presentation Phase Angle plotted against Frequency Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 77 Approach Line graph presentation Force Moment plotted against Frequency Surface graph presentation Phase Angle plotted against Frequency Frequency Surface graph presentation Force Moment plotted against Frequency Frequency The Frequency Scale can be modified to be Period Scale if required Line Graph Input e Use the Component input to select which force component to plot either X Y or Z
71. cting structures in addition to any structures that you want to exclude for this particular analysis It also enables the structure order to be changed Structures can be selected graphically use the CTRL key to select more than one for inclusion in a group or to be excluded from the analysis To include structures in a group click on an Interacting Structure Groups field To exclude structures from the analysis click on the Structures to Exclude field Select the structures in the model then click the Apply button The selected structures will be listed in the field If a structure is excluded then it will automatically be removed from any groups and the structure order A structure may only be included in one interacting structure group By default when Aqwa is first started all parts will be considered to be hydrodynamically interacting and will be included in the analysis If a part is subsequently suppressed it cannot be used in the ana lysis and is automatically excluded in the Structure Selection However when a part is then unsuppressed it must be manually added to the Structure Selection in order for it to be included in the analysis If hydrodynamic interaction is required then this must also be established manually in the Structure Se lection If a structure has been removed from the analysis and you want to add it back in you must reselect the set of Structures to Exclude If you want all structures to be included in the analy
72. ction of the force exerted by the cable is undefined and is automatically set to zero Note If a cable is not defined properly before running the analysis the cable will be drawn as a straight red line between the start and end and an error will be reported in the Message window Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 20 of ANSYS Inc and its subsidiaries and affiliates Define Connections 2 4 1 1 Linear Elastic For linear elastic cables a Stiffness and Unstretched Length need to be defined and up to two pulleys can be defined along the line This is a very simple type of cable simply a tension only spring where the tension is proportional to its extension and the constant of proportionality is termed the stiffness As the extension may vary during the analysis the structure s to which the cable is attached will experience a force of varying magnitude and direction The magnitude of this force which is equal to the cable tension is given by Force Stiffness x Cable Extension Note that when the cable is slack the cable extension is negative and the cable tension is set to zero Pulleys A Pulley has the effect of intersecting the cable and will effectively extend the cable to pass via the pulley position Adding a second pulley will extend the cable further from the first pulley to the end of the cable hence the cable will travel from the cable start
73. ctor The gust factor G t z can be defined as G t z Uz t Uz 1 9 t I z where z turbulence intensity see below t gust duration seconds The factor g t is given by g t 3 0 In 3 t 0 6 for t lt 60 seconds Turbulence Intensity Turbulence intensity is the standard deviation of wind speed normalized by the mean wind speed over 1 hour Turbulence intensity can be approximated by I z s z Uz 0 15 zs z 0 125 for z lt zs 0 15 zs z 0 275 for z gt zs where zs 20m 66 feet thickness of the surface layer We note that the turbulence intensity at 10m is 0 1636 or the ratio of U10 standard deviation at 10m is 6 112 1 0 0 1636 Wind Spectrum S f f 1 1 5f 5 3 where f non dimensional frequency F fp Measured values of fp show a wide variation An average value given by fp 0 025 Uz z is currently used in Aqwa i e f 40 F z Uz The spectral energy density S F is given by S F s z 2 S f F Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 61 Approach We note that by definition the integral 0 to infinity of S f F is unity 2 7 10 3 NPD Standard Spectrum This spectrum is based on the NPD spectrum as defined in API RP2A 21st edition with supplements In the following all quantities are measured in SI units m m s Mean Profile The mean prof
74. d by the Connectivity field in the Details panel of the object using the connection points To add a connection point on a structure click on the Part object in the tree and from the Add menu in the toolbar or the right click menu select Connection Point To set the initial position of the connec tion point click on the Connection Point object that was added and do one of the following Set Definition of Position to Coordinates and set the Position Coordinates X Ordinate Y Ordinate Z Ordinate in the Details panel Set Definition of Position to Vertex Selection Click on Select a Single Vertex in the Vertex field select a vertex on a structure and click Apply You can then set an X Offset Y Offset or Z Offset from the vertex if needed Note Even if you define the initial position of the Connection Point using Coordinates or with an offset from a vertex on the Part the connection point is attached to the part and will move with the part maintaining the relative position that you defined when you created it 2 4 Define Connections The Connections object allows you to create connections between structures or between structures and the environment The available connections are 2 4 1 Cables 2 4 2 Catenary Data 2 4 3 Connection Stiffness 2 4 4 Fenders 2 4 5 Joints 2 4 1 Cables Aqwa supports four types of cables each with their own input requirements e Linear Elastic Non Linear Polynomial
75. d the equilibrium position will be determined before the Time Response analysis is started and used as the Starting Position If the starting position is set to Based on Geometry the current geometry will determine the Starting Position If there is an upstream Hydrodynamic Time Response system then this option will be read only and set to Program Controlled as it is determined by the position at the end time of the upstream system Use Cable Dynamics If Yes enables cable dynamics to be used can be set per cable If Cable Dynamics is disabled then re gardless of the selection in the individual cable it is not used during the analysis 2 6 2 Output File Options The analysis settings available in this section of the Details panel control what is written to the Aqwa output text file or to specific additional files refer to the Aqwa Reference manual Help gt Aqwa Refer ence from the Aqwa Editor menu bar for more details Output ASCII Hydrodynamic Database If Yes prints the hydrodynamic database the HYD file in a compact ASCII format to a new file with a AH1 extension This option must be set to Yes in order to use the Output Example of Hydrodynamic Database option Output Example of Hydrodynamic Database If Yes prints a sample of the AH1 file with annotation to explain the format Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 40 of ANSYS Inc and its subsidiaries a
76. e Coefficients window that appears below the model Enter the Direction of the wind 180 to 180 degrees the X force coefficient Translation X Y force coefficient Translation Y Z force coefficient Translation Z Rotation about X coefficient Rotation X Rotation about Y coefficient Rotation Y and Rotation about Z coefficient Rotation Z The number of rows is increased as each entry is made up to a maximum of 41 rows Note that the forces are in the directions of the axes not in the direction of the wind For example for relative wind velocity V in direction force in X direction WIFX V7 force in Y direction WIFY V moment about Z axis WIRZ V where WIFX WIFY and WIRZ are the coefficients Similar equations apply for force in Z and moments about X and Y The coefficients are applied in a moving axis system in other words the axes move with the structure Since there is no structure local axis system available the initial coefficient data must be defined relative to the global coordinate system when the structure is in the position as defined in the geometry For example Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 17 Approach WIFY 2 WIFX 2 Position Defined in the Geometry wnt gt Global Coordinate iets Sysetm Wy FY Wp x Position During Simulation Note
77. e Non Linear Steel Wire e Non Linear Catenary Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 19 Approach To add a Cable click on the Connections object in the tree From the Connections toolbar or the right click menu item Insert Connection then select Cable The type of the cable Linear Cable Polynomial Cable Steel Wire Cable or Catenary Cable can be set in the details panel Cables may either be joined between two structures or a fixed point and a structure this option can be changed via the Connectivity field in the Details panel In both cases an End Connection Point must exist at the position of the end of the cable this can be selected from a dropdown of existing Connection Points defined on the structures When the starting point is on a structure you can define the start of the cable using Start Connection Point which again is a dropdown of existing connection points defined on the structures When the starting point is a fixed point a Fixed Point drop down list of defined fixed points is shown Linear Elastic and Polynomial cables can be winched by adding a Cable Winch All cable types can also have break conditions based on tension or time defined by adding a Cable Failure object Set additional options in the Details panel for each cable type as described in the sections below The extension of the cable
78. e Options 2 6 3 QTF Options 2 6 4 Common Analysis Options Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 39 Approach 2 6 1 Time Response Options The analysis settings in this section of the Detail panel are available for Time Response systems Analysis Type Select one of the analysis types listed Depending upon the type selected either a regular or irregular wave object needs to be defined for the analysis Available settings are e Irregular Wave Response With Slow Drift Irregular Wave Irregular Wave Response Irregular Wave e Regular Wave Response Regular Wave Slow Drift Only Irregular Wave Start Time Finish Time Set the Start Time and Finish Time for the Time Response simulation Then either set the Time Step or Number of Steps the other parameter will be updated to reflect the selected value If there is an upstream Hydrodynamic Time Response system the Start Time will automatically be set to the end time of the upstream system Time Step Number of Steps The values of these fields determine the number of steps in the analysis Time Step and Number of Steps are interrelated and an update of one will affect the other to ensure consistency between the entries Modifying Time Step duration will modify the Number of Steps and vice versa Starting Position If Starting Position is set to Program Controlle
79. e added to the end of the table and they will be automatically re sorted once entry is complete Position data can also be copied and pasted from an appropriate external source Defining the XFT file The time defined in the data does not need to match the time step defined in the analysis the program will interpolate the forces when necessary using a cubic spline interpolation technique When modeling periods of constant force adequate data points must be provided to satisfy the interpolation method There is no limit on the length of the XFT file It is important to note that the forces defined in the XFT file are in six degrees of freedom for each structure and are in the global axis system Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 48 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces Comment lines are permitted at any point in the file and must begin with The first line comments excepted in the file ought to contain the structures information this indicates the structure numbers that the columns correspond to For example when there are 3 structures this line could be structures 1 3 9 The structure numbers can be determined from the Aqwa Editor by reviewing the Structure Selection in the upstream Hydrodynamic Diffraction analysis Before the data defining the time and forces there must be a line containing only the text
80. e adjacent check box 2 8 3 Hydrodynamic Pressures and Motions Results The Pressures and Motions results object enables the visualization and display of a number of results generated from Aqwa once a hydrodynamic solve has been performed Any number of Pressures and Motions results may be added You can filter the structures Parts that are shown in the result The Structure filter field provides a dropdown list that allows you to select any of the structures in the Geometry or All of the structures If the structure that you select is part of an Interacting Structure Group by default all structures in the Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 86 of ANSYS Inc and its subsidiaries and affiliates Solution group will be included in the result To exclude the other structures in the group set Include Interacting Strs to No The Frequency and Direction options available will be those that exist for all selected structures which were last successfully analyzed hydrodynamic solve or those currently specified if no analysis has been undertaken If a frequency or direction is selected and then on a subsequent analysis not analyzed then the option will default to the first available frequency or direction The Incident Wave Amplitude can be modified to provide results that are factored from the unit 1m wave that is the default extreme modification may extend results bey
81. e graph presentation Phase Angle vs Frequency or Direction e Surface graph presentation Force Moment vs Frequency Direction Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 78 of ANSYS Inc and its subsidiaries and affiliates Solution Surface graph presentation Phase Angle vs Frequency Direction The Frequency Scale can be modified to be Period Scale if required Line Graph Input e Use the Component input to select which force component to plot either X Y or Z for forces or RX RY or RZ for moments e When the plot is performed against Direction then the required frequency can be chosen using the Fre quency input e When the plot is performed against frequency then the required direction can be chosen using the Dir ection input When Force Moment plots are performed the SubType field is shown to enable the selection of the full Amplitude component or just the Real or Imaginary components e When Force Moment plots are performed use Bounding Box Min Coordinate X Y Z to enter the co ordinates of one corner of a bounding box and Bounding Box Max Coordinate X Y Z to enter the co ordinates of the opposite corner of the box Then enter a Calculation Coordinate X Y Z to enter the coordinates of the point about which the moments are calculated Values entered should be separated by spaces Line Graph Output Maximum Value and Minimum Value of Angl
82. e options available are Program Controlled or User Defined If you select User Defined you can set the seed value Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 50 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces Number of Spectral Lines Definition defines the number of individual components used to simulate an irregular wave The options available are Program Controlled or User Defined If you select User Defined you can set the Number of Spectral Lines up to the maximum of 200 Note The new user is strongly advised to use the Program Controlled option The program will automatically generate the appropriate number of spectral lines for the particular method of analysis and it is only in unusual circumstances that user input is required In the case of a spectrum imported from a Wave Height Time History WHT file the analysis will always use 200 lines and the user will not be allowed to modify this value Omit Calculation of Drift Forces disables the mean drift force calculations for the current spectrum Select Yes to disable the calculations and No to have them applied The user should in general specify a spectral sea state whose range of frequencies is less than the range for which the hydrodynamic parameters for the structure are defined those specified in the Wave Frequencies object At spectrum frequencies which are
83. e or Force Moment and the first Frequency or Direction at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Surface Graph Input e Use the Component input to select which force component to plot either X Y Z for Forces or RX RY RZ for moments When Force Moment plots are performed the SubType field is shown to enable the selection of the full Amplitude component or just the Real or Imaginary components When Force Moment plots are performed use Bounding Box Min Coordinate X Y Z to enter the co ordinates of one corner of a bounding box and Bounding Box Max Coordinate X Y Z to enter the co ordinates of the opposite corner of the box Then enter a Calculation Coordinate X Y Z to enter the coordinates of the point about which the moments are calculated Values entered should be separated by spaces Surface Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the Frequency and Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 1 7 Bending Moment and Shear Force Static Bending Moments and Shear Forces can be calculated by the SF BM Static result either all pressure components or only the Z component can be chosen For these result types the results are always plotted alon
84. e tension will be varied according to whether the range distance between the anchor and vessel attachment point is increasing or decreasing If the range is less than the initial length specified the line becomes slack and the tension is zero To set up the constant tension Cable Winch object click on the object In the Details panel Select Maintains Constant Tension from the Cable Type dropdown list Select the cable to associate with the winch from the Cable Selection dropdown Enter the value of the Winding In Friction Enter the value of the Paying Out Friction Enter the desired Winch Tension value Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 67 Approach 2 7 11 2 Winch that Changes Cable Length Cable Winches that change the cable length can only be used with Linear Elastic without Pulleys In the case when the winch changes the cable length it can be made to start at the given speed after the start time and pauses if the maximum tension is exceeded The winch will stop paying out or winding in when the final length is reached An additional length La can be entered to affect the initial stiffness of the cable and the maximum stiffness Kmax AE La The initial stiffness of the line KO is used which is equal to EA L La for the line E Youngs modulus A cross sectional area The stiffness of the
85. e user is aware of the results orientation this does not have to be respected in DesignModeler Figure 2 7 Line Graph JaA NDR RACI m ta w ee Fon Fores ON TOR S RRRA ee Dotad of RAs Response Amplitude Operators aAa Reworwe igde Preuertaton Me tod Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 72 of ANSYS Inc and its subsidiaries and affiliates Solution Figure 2 8 Surface Graph 1655722000 1670 0 09 HNOS 19407 11135100 35 2 nmmn AH DINN 63 mann ree LIAIS TROD 172144794 TTL TAS SOHO TDA GNTS TLS TPKE ADS BORD JPS 470078125 OQ Oe ke IIIS MOS3A 075 SO O87 MAHI TS MOS ANASA IAAI IAS ORC tT Sat il Mn To et moas TAS ortas ZMOOT Se ITE Ree Aaea as 301377 21913372S Jehaj Tees N ite a et Sa 2 2750039 3NA IDeA I INR MUGS ON CHES ta ae ee ee SAN eum ee DNWLS ONS 473015 or TeS WIA SN 77000 me SET span s7mess 1000217 Jass sod nr DINI 7 wsv mam sees 19902306 mona Le wam D pai 2a gt az vse raram me we 14 1404 E pans vines Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 73 Approach Figure 2 9 Surface Contour Graph m en Vow u te Foe F ON TOO IStRQRMQGeM SOR rectors Pe Nae MEDA AL Soton a5 sD roere Gan 4D Mocim Gan oh rodra Gh s Mima Gah ast peers OTs Quate T
86. e will open You can enter text do some basic formatting change the background and foreground colors and add pictures to the comment In the Details view you can enter an author name in the Name field Comments will appear in a generated Report under the parent object in the tree Figure 4 2 Comment Edit Pane aval Wen 7 Brule Ral MA Put Comment Here Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 98 of ANSYS Inc and its subsidiaries and affiliates Comments Images and Figures 4 3 2 Images You can insert an Image object in the tree or save the current Model view to a file by clicking on the New Figure or Image button in the toolbar Figure 4 3 New Figure or Image Menu ai E Figure 9 Image amp Image from File 6 Image to File From the drop down menu you can select Image to insert an Image object in the tree containing a snapshot of the Model s current view in the Geometry window Image from File to insert an image from a file as an Image object in the tree Browse to an existing bmp jpg or png file to insert the image Image to File to save the Model s current view Browse to the desired location and chose the file format png omp jpg tif or eps In the Details view you can enter an annotation for the image in the Text field Image objects will appear in a generated Report under the parent object
87. ely Internal Lid and External Lid can be used to suppress standing waves either between structures or within structures Note Automatic internal lids can be selected using the Part option If the generation of an external lid is specified two additional parameters are required The first is a Lid Damping Factor set between 0 and 1 The factor represents how effective the lid is to be 0 will result in no effect while 1 will prevent any vertical water surface velocity under the lid The second parameter is the Gap for Lid It is a representative size for the lid typically the distance between the two vessels or the width of a moon pool It enables the lid properties to be tuned to the resonant frequency of waves in the gap 2 3 2 Line Body Line bodies are used to create single elements for Aqwa How they are interpreted depends upon the cross section of the line if it has a circular cross section then it will be automatically converted into a tubular line and will create standard tubular TUBE elements All other sections will create slender tube STUB elements The content of the details pane changes considerably depending upon the type of line The details are discussed below Line type Tubular If the line in Design Modeler was defined with a tubular section the line body will default to this setting the tube Diameter and Thickness are automatically read from the Design Modeler data along with the calculated inertia valu
88. es Use Tube Type to make the tube Sealed or Floodable By default the tube is sealed and in this case the tube would be buoyant however the tube does not have longitudinal drag or added mass unless discs are created at the ends Discs can automatically be applied at either Created at End A Only Created at End B Only or both Created at Both Ends ends with the Tube End Discs option if you choose one of these options default disc parameters are used If you require different parameters discs can be ex cluded here and added manually A Viscous Drag Coefficient and Added Mass Coefficient can be defined although drag is not used in Hydrodynamic Diffraction or hydrostatic analyses A density of the tube Material Density is also required this defaults to the standard value for steel Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 11 Approach Line type Stub For all sections other than tubular only the inertias will be obtained automatically from the parameters that are entered in Design Modeler If a stub element is not required then it is possible to change it to a tubular line and define the diameter and thickness within the Aqwa Editor There are options to change the diameter of a stub element in both the local Z and Y directions Z Diameter Y Diameter as well as the Cross Section Area For Aqwa valid cross sect
89. es and 3D surfaces can be plotted in addition to a contour surface plot The chart type and axes will be based on the selection that you make from the right click menu when you add the object to the Solution Once you have created a graph object you can select it and edit its properties in the Details pane After inserting a new graph or changing input in an existing graph the results need to be evaluated The update results option is available via the context right click menu Any number of objects can be added to the Solution and up to 4 compatible line graphs can be com pared within each object Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 71 Approach A Maximum and Minimum value for the plotted parameter will be shown in the Details panel and will also be highlighted in the data table minimum is blue and maximum is red Multiple entries are highlighted in the table if they have the same value The positions of the Minimum and Maximum points are also given in the Details panel The lower right corner of the graph window contains a control that allows you to zoom and pan on the chart by selecting the corners of the control to zoom and the center to pan Note Aqwa always produces results in global coordinate systems traditionally the ship is defined with its longitudinal axis in the global X direction However if th
90. es and Line Bodes as needed You can attach a geometry that has no line or surface bodies but this is not appropriate for an Aqwa analysis You can also set the Geometry import options on a per system basis When a system is initially created the default geometry import settings will be used If you would like to change the import settings for a particular system right click on the Geometry cell in that system and select Properties Use the check boxes in the Properties view to set the items to import for this system These settings are sent to the editor to use on edit or import If you change the settings after initially editing the model you will need to refresh the cell or edit and refresh to consume the change and reattach the geometry with the new CAD import settings 2 2 2 Configuring the Geometry On opening a hydrodynamics analysis system the Aqwa Editor will automatically attach the geometry Each part becomes a separate structure in Aqwa If a structure is to be formed of both diffracting and non diffracting elements these should be in separate defined bodies within the multi body part When attaching a geometry the units also change to be those of the model these can be modified via the units menu if desired The hydrodynamics systems assume the still water surface lies on the XY plane and Z is positive up All structures are located in a global analysis space note that Hydrostatic Results and Hydrodynamic Graphical Result
91. es derived from the Hydrodynamic Diffraction system results This can be used to limit the transient at the start of a simulation Use Linear Stiffness Matrix to Calculate Hydrostatic If Yes uses the linear stiffness matrix rather than recalculating the hydrostatic stiffness from the hydro static element model This normally will reduce the time to run the program substantially Use Slow Velocity for Hull Drag Calculation If Yes uses the slow velocity drift frequency velocity for the hull drag calculation instead of the total velocity drift frequency velocity wave frequency velocity which is the default Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 45 Approach 2 7 Applying Ocean Environment and Forces The following ocean environment and forces objects can be added to your analysis or may be included with your analysis by default Some are restricted to the Hydrodynamic Diffraction analysis and some are restricted to the Hydrodynamic Time Response analysis 2 7 1 Structure Selection 2 7 2 Gravity 2 7 3 Wave Directions 2 7 4 Wave Frequencies 2 7 5 Structure Force 2 7 6 Regular Wave 2 7 7 Irregular Wave 2 7 8 Irregular Wave Group 2 7 9 Current 2 7 10 Wind 2 7 11 Cable Winch 2 7 12 Cable Failure 2 7 1 Structure Selection The Structure Selection tree object enables the definition of intera
92. eterized by selecting the adjacent check box 2 8 2 2 4 Structure Forces Result Description 2D graphs to illustrate the following response subtypes of the Structure Forces during the analysis All Mooring Sum Only e Gyroscopic Only Diffraction Only e Linear Damping Only e Morison Drag Only Drift Only Froude Krylov Only e Gravitation Only Current Drag Only Wave Inertia Only Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 83 Approach e Hydrostatic Only e Wind Only Slam Only e Point Only Yaw Drag Only Slender Body Only Radiation Only Fluid Momentum Only Fluid Gyroscopic Only Externally Applied Only Linear Wave Drift Damping Only The sum of forces for each individual subtype will be shown in the graph If all of the forces are taken in combination they will form the result available by the All subtype In the case where the force is not included in the analysis e g Drift Forces when drift is excluded the subtype will produce zero values Note The Point Only includes forces that have constant direction relative to the structure i e the global direction may change Where the global direction is constant these are included in the Mooring Sum Only as they are normally formed of a cable attached to the vessel When including drift effects the Froude Krylo
93. f the force is given by FD 0 5 p CDA VR VR where CDA Drag coefficient projected area 2 4 3 Connection Stiffness This object may be used to input a connection stiffness matrix between structures using tabular input in the Matrix Definition Data window Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 25 Approach The Connectivity can be set to Fixity amp Structure for a structure connected to a point or Structure amp Structure for two connected structures Select the first and second if present structure in the Connected Structure A and Connected Structure B fields Note A Connection Stiffness object only applies to a hydrodynamic diffraction analysis If you want to include the effects of Linearized Morison Drag in the analysis you cannot have two structures connected with a Connection Stiffness matrix To add a Connection Stiffness Matrix 1 Right click on the Connections object and select Insert Connection gt Connection Stiffness or Click on the Connections object and select Connection Stiffness from the Connections toolbar A Connection Stiffness object is added under Connections 2 Select the Connection Stiffness object in the Tree Outline and enter the matrix coefficients in the Matrix Definition Data window that appears below the model 3 Set the Connectivity and structure info
94. ficient Friction coefficient for axial force k3 e Constant Friction Moment Constant friction moment k4 The frictional moment is given by M e k1V Fj F2 121 M5 M2 135 k4 where 0 if the relative rotational velocity is less than 0 001 rad s 1 otherwise k1 k4 are coefficients Note that these are not conventional dimensionless friction coefficients as used in the equation F UR These coefficients are factors to be applied to the appropriate forces to give frictional moments and they must include effects of the bearing diameter etc k1 k3 must not be negative k1 and k3 have dimensions of length and the maximum value allowed is 0 025g 9 81 where g is the acceleration due to gravity k2 is non dimensional and has a maximum value of 0 025 When inserting a joint two axis objects are inserted as its children Joint Target Axes and Joint Contact Axes These axes objects define the orientation of the two objects that are connected by the joint The orientation can be set using these fields in the Details panel for each axes object Alignment Method Select Global Axes to align the axes with the global axes You can also set the alignment of the axes using the Vertex Selection or Direction Entry methods Origin Vertex X Direction Vertex Vertex Defining the XY Plane For an Alignment Method of Vertex Selection select the Origin Vertex of the axis a vertex defining the X direction X Direction Vertex
95. fixed by setting Structure Fixity to Structure is Fixed in Place Fixity primarily affects the results of a hydrodynamic diffraction analysis by impacting the structure s RAOs It therefore also has an impact on the hydrodynamic time response results as the calculated drift forces depend on these RAOs It is thus necessary to impose the coherence between the setup of the two analyses by fixing the structure in the time response analysis Since the user can create joints to be used in time response analysis it is the user s responsib ility to create a rigid joint when it is connected to a fixed point on any Part marked as Fixed in the Details dialog Not doing so will result in an error when solving the time response analysis The Mass Factor and Drag Factor provide a way of modifying the added mass and drag coefficients defined for any tube and disc elements associated with this part This may be used for parametric studies where the effects of Morison drag on appropriate elements are considered important e g sim ulating tests at model scale These factors have no effect on any other object type in the part The Slam Factor provides a way to enable the computation of slamming loads on tube and disc elements By default a factor of zero is specified which disables this computation Any positive non zero value will cause the program to compute the slam coefficient for each applicable element based on the premise that the slam force is equal to the r
96. formation of ANSYS Inc and its subsidiaries and affiliates Chapter 2 Aqwa Approach This chapter takes you through the different steps required to setup a hydrodynamic analysis 2 1 Import or Create Hydrodynamic Analysis Systems 2 2 Attach Geometry 2 3 Define Parts Behavior 2 4 Define Connections 2 5 Mesh 2 6 Establish Analysis Settings 2 7 Applying Ocean Environment and Forces 2 8 Solution 2 1 Import or Create Hydrodynamic Analysis Systems You can import an existing Aqwa Editor v12 0 database into Workbench or you can create a new hy drodynamic system in the Workbench Project Schematic 2 1 1 Import a Hydrodynamic System Database 2 1 2 Create a Hydrodynamic Analysis System 2 1 1 Import a Hydrodynamic System Database To import an existing hydrodynamic system database do the following 1 In Workbench click on the Import button or select File gt Import 2 In the Import window select Files of type AQWAWB Database aqdb 3 Click on a aqdb database and select Open to open the Aqwa Editor and create an Aqwa Hydrodynamic Diffraction system for each Analysis contained within the database The above technique may be used to duplicate complex connected systems that you cannot otherwise replicate using the Duplicate function Once saved in Workbench as a Workbench project you may use Workbench File gt Open to open an existing Workbench Project containing hydrodynamic systems 2 1 2 Create a Hydrod
97. formation is imported See Report Preview for more information on generating reports 4 2 Parameters Certain quantities in your Hydrodynamic analysis can be exposed to the Workbench environment as parameters A parameter may be exposed by selecting the checkbox next to its Detail field which shows a P when selected Parameters can be used in post processing to conduct optimization analysis and what if scenarios See Working with Parameters and Design Points for more information about working with parameters Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 97 Common Features Figure 4 1 Example of Parameters in the Details View Pree Pi fo Help 4 3 Comments Images and Figures You can insert Comment objects Image objects and Figure objects under various parent objects in the tree to add text or graphical information that pertains specifically to those parent objects These objects can all be deleted from their parent objects by right clicking on them and selecting Delete 4 3 1 Comments 4 3 2 Images 4 3 3 Figures 4 3 1 Comments You can insert a Comment object in the tree by clicking on the Comment button in the toolbar Aj A window pane will open below the main graphics pane displaying a text box where you can enter the comment Any time you click on the Comment object in the tree this comment edit pan
98. fraction A4 vin Analysis Settings y Gravity D Structure Selection y Wave Directions 9 Wave Frequencies Solution A5 OD Pemesan Results objects add as wie required for each view Analysis input objects for defining AQWA analysis data Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 93 Workbench Interface For a description of a particular tree object select a link from below If you are an existing Aqwa user then you may also find the section Information for existing Aqwa users p 103 a useful comparison of capabilities and definition methodology Each object in the tree has properties that are used to control the analysis and view the results Each object has a different function which is described in the table below For some objects the right mouse button can be used to insert additional objects under that object such as masses or result views Altern atively the dynamic toolbar can be used to insert additional objects Table 3 3 Definition of Tree Objects Project Define Basic Project Information Model Define Model Folder Geometry Attach Geometry and Define Basic Info Parts Structures Define Structure Geometry Details Surface Bodies Define Surface Geometry Details Line Bodies Point Mass Define Line Geometry Details Define Point
99. fsets Note The vertical position of the vertices selected for the central line end points is irrelevant the vertical position of the central line is set by Depth to Bilge Additional Hydrodynamic Stiffness Damping and Added Mass can be added to the Part object using the context menu or from the Add menu on the toolbar when the Part is selected Use the context right click menu or the toolbars to add additional Aqwa specific elements into the geometry such as Point Mass Point Buoyancy Disc Wind Force Coefficients and Current Force Coeffi cients You can remove any of the objects by right clicking on them in the tree and selecting Delete from the context menu Geometry pAdd v Point Mass Point Buoyancy amp Disc Fixed Point oe Connection Point 3 Additional Hydrostatic Stiffness Additional Damping 3 Additional Added Mass z Wind Force Coefficients he oan 3k Current Force Coefficients A full list of the types of bodies is 2 3 1 Surface Body 2 3 2 Line Body 2 3 3 Point Mass 2 3 4 Point Buoyancy 2 3 5 Disc 2 3 6 Additional Hydrodynamic Stiffness 2 3 7 Additional Damping Frequency Independent 2 3 8 Additional Added Mass Frequency Independent 2 3 9 Current Force Coefficients 2 3 10 Wind Force Coefficients 2 3 11 Structure Connection Points 2 3 1 Surface Body Surface bodies are areas that can be meshed to create diffracting or non diffracting elements for the Aqwa analysis The name
100. g the vessel Alternatively response amplitude operator RAO based results can be Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 79 Approach determined for each wave direction and frequency and position Depending upon the combination of requirements these will be shown on both 2D and 3D graphs appropriately When graphs are plotted against Position the Frequency or Direction can be explicitly selected or they can be enveloped so that the critical result can be identified easily When graphs are not plotted against Position then the calcu lation Position can be specified and if appropriate the Frequency or Direction can be explicitly defined in this situation they cannot be enveloped For all Bending Moment Shear Force results enter a Neutral Axis position in the Details panel this is located relative to the global coordinate system Bending Moment and Shear Force calculations depend upon the masses being accurately defined in the geometry section and will only be permitted if there is only a single structure in the analysis and the positions along the vessel are defined in the X direction Result Description 2D or 3D graphs to illustrate the shear forces bending moments applied on the structure and how they change with direction frequency position or combinations of direction frequency position Plot availabilit
101. hen the geometry was created If more than two structures are part of the group to be broken apart the program positions both subgroup structures where they would have been if the two subgroups had been originally created with the remaining joints The suppressed and deleted joints are not considered as part of the new arrangement The existing joints are applied in chronological order Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 36 of ANSYS Inc and its subsidiaries and affiliates Mesh 2 5 Mesh The options in the Details panel of the Mesh object are global options that apply to all of the unsup pressed parts and bodies There are also local mesh control objects that can be added to the analysis to override the settings on particular parts or bodies in the analysis These parameters apply to the whole structure although parts or bodies of the structure can be sup pressed to prevent unnecessary meshes being created If suppressed they will be excluded from the analysis and subsequent result display Use the toolbar item or context menu to generate the mesh Mesh Generate Mesh Note It is not yet possible to employ symmetry in Aqwa hence the full model must be meshed There are basic and advanced global mesh settings available as well as the ability to add additional mesh objects to perform local mesh operations These are described in the following sec
102. hen the plot is performed against Frequency then the required direction can be chosen using the Dir ection input Line Graph Output Maximum Value and Minimum Value of Angle or Distance Rotation and the first Frequency or Direction at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Surface Graph Input Use the Component input to select which degree of freedom to plot either X Y Z for translation or RX RY RZ for rotation Surface Graph Output Maximum Value and Minimum Value of Angle or Distance Rotation and the Frequency and Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 1 3 Radiation Damping amp Added Mass Result Description 2D graphs to illustrate how the Radiation Damping or Added Mass varies with frequency Plot availability Line graph presentation Radiation Damping or Added Mass plotted against Frequency The Frequency Scale can be modified to be Period Scale if required Line Graph Input Use the Subtype and Component inputs to select which value from the Radiation Damping or Added Mass matrix to plot X Y Z for linear components or RX RY RZ for rotational components Line Graph Output Maximum Value and Minimum Value of Radiation Damping and the first Frequency at which
103. ile for the wind speed averaged over 1 hour at elevation z Uz can be approximated by Uz U10 1 C In z 10 where U10 Wind speed averaged over 1 hour at reference elevation of 10 metres C 0 0573 V 1 0 15 U10 Turbulence Intensity Turbulence intensity is the standard deviation of wind speed normalized by the mean wind speed over 1 hour Turbulence intensity can be approximated by I z o0 z Uz 0 06 1 0 043 U10 z 10 0 22 Wind Spectrum 2 azg 10 Sf a 1 f where S f spectral energy density at frequency f m 2 Hz f frequency Hz 2 172x faa J 3 U10 4 10 In some places in Aqwa non dimensional values are output The non dimensional NPD spectrum is calculated as s f S f f o 10 2 where o 10 I 10 U10 is the standard deviation at z 10m Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 62 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces 2 7 10 4 ISO Standard Spectrum This spectrum is based on the ISO spectrum as defined in ISO 19901 1 2005 E It is the same as the NPD spectrum except that the frequency range is limited to 0 00167 Hz lt f lt 0 5 Hz 2 7 10 5 User Defined Spectrum The user defined wind spectral energy density S F at a frequency F Hertz is defined as S F S f s z 2 F where the non dimensional frequency f is defined as f cf F z
104. in the table there will be a number of arrows to represent the current direction and speed at various depths these will be purple if valid or yellow if invalid For a constant current a single arrow is shown at the depth defined in the Current Definition Data table The arrows are scaled with speed For each structure Part the depth at which the current velocity is calculated Current Calculation Depth for the hull loading can be entered in the Part details again this should be a positive number Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 57 Approach got r Details a Details of Part Name Part Part Visibility Visible Part Activity Not Suppressed Generate Internal Lid No Current Calculation Depth Om Fixity Options Note Current cannot be parameterized If a User Time History of wave elevations is imported using a WHT file it may be necessary to define the current profile with negative velocities 2 7 10 Wind To supplement the wave forces being applied to the structure wind forces can be modelled Wind can be modelled using a number of spectrum options including user defined user time dependent data or constant velocity The wind is shown in the graphic by an arrow at the reference height or at ht 0 if not applicable scaled with speed To insert a Wind object in your Time History a
105. inch drum can only be switched at the beginning or the end of a time step and NOT in the middle In order to conserve energy momentum in the equations of motion the length of the line can only be changed in steps of time step speed of the winch The tension resolution will therefore be stiffness time step speed Large stiffnesses or drum speed should therefore be specified with appropriately small timesteps If the unstretched length of the cable is less than 0 1m it will be defaulted to 0 1m 2 7 12 Cable Failure A cable can be defined to fail when a given tension is reached and or after a specified period of time This behavior is governed by the selection in the failure mode drop down after which options for se lecting the cable along with time and critical tensions at each end of the cable can be entered Note that the tension in a cable will be the same at the start or the end of the cable unless Non Linear Catenary cables are used To add a Cable Failure object click on the Hydrodynamic Time Response system then select Cable Failure from the Analysis toolbar or from the right click menu Insert gt Cable Failure To set up the Cable Failure object click on the object In the Details panel select the cable that you want to fail from the dropdown list Failing Cable Select one of the following for Failure Mode and enter the parameters for that failure mode At given time enter the analysis Failure Time at which the ca
106. ine GONMECHONS oeir serenana nena ekaa EE a aE EE EEA E ea AAEE aa PaE Ea R REE Ri ei 19 DAV EA EE AA A A EEA EE N TE AAE EAA EE 19 2 4 1 1 Linear Elastic ccecceccdeecsee tech ead ote e a a a E aae a EA Te EEL etea 21 24 1 2 Non Linear POLNOMMAl ssnin aa e e A A E A ATA 21 2 4 1 3 Non Linear Steel Wire ccccccccccessssssnsneccccceceseesnnneeeeceecesseessaeeeeeeceeeseesnaaeeeeeeeeseeenenaeess 21 ZAAA NON LINC AL Catenary v sisicccasicaticescatcccnaaertioeseededtenaien E O EEE EE EERE NECE ETRE E S 22 24 2 Catenary Data sevicsiessiiowssiucstchcteaits ueiba lave E E EN ss ucecabea datuandcuouectea nba latuanesbin dadnets 23 24 2 1 Catenary SCCUOM asses nn eene a De watenesepatantea tenes E EE E E a 24 24 2 2 ELATI a E E E E E E E E E 25 24 3 CONNMECHON SUIPFMESS eade odena st a naaie aneas na e aor aa aeaa iea Raa aaaeei ai Raa Kaapin a ia cance 25 24A Fend rS a ee ea E ESEE EEEE AE EEAO ai E EEEa aarti aad 26 2 4 4 1 Examples of Use of Fenders cccccccccsssssssnsecccceecesssssneeeceececesseessnaaeeeeeeeceseeesnnaseeeeeseeeees 28 DAS JOUMUS i cela seasaavics cadences E aA E E E AOA AEA EE A E ER 30 2 4 5 1 Initial Positioning of Jointed Structures essssseesssseesssesessssreessssressssrressseressseresssseresssee 33 245 2 MOVNO Structures itn n E E E O 34 24 53 Closed LOOPS hrnie re a a r a a E a as 34 2A 5A REMOVING AJON ria e cies as tnt e EA EEEE sa cg E a E EE eaa 36 PAA EI DAE AE E NTA E A NENA E TAA E NA E 37
107. ion Point 1 Part Contact Connection Point Connection Point 2 Part 2 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 28 of ANSYS Inc and its subsidiaries and affiliates Define Connections Uni Directional Fender Aligned to X Axis Details of Fender 1 C e X Direction Oriy Fender Connection Point Connection Point 1 Part Contact Connection Point Connection Point 2 Part 2 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 29 Approach Uni Directional Fender Aligned to Z Axis q Details of Fender 1 C SSSS d ner CS Visibility Visible Activity Not Suppressed Connectivity Fender And Contact On Structures Type Fixed Action Z Direction Only Fender Connection Point Connection Point 1 Part Contact Connection Point Connection Point 2 Part 2 2 4 5 Joints A hydrodynamic analysis allows structures to be connected by articulated joints These do not permit relative translation of the two structures but allow relative rotational movement in a number of ways that can be defined by the user To add a joint to your analysis right click on the Connections tree object and select Insert Connection gt Joint or click on the Connections object and select Joint from the Connections toolbar To add a joint you will need to enter the
108. ional areas vary between an ellipse and a rectangle with the width and height of the two diameters In addition you can specify a Viscous Drag Coefficient and Added Mass Coefficient in each of the Z and Y directions It is also possible to define the mass contribution of the stub to the model Mass Unit Length You cannot automatically add Discs to STUB objects but you can add them manually if needed 2 3 3 Point Mass Point mass elements can be inserted into the model the properties can either be input manually or can be Program Controlled If Mass definition is set to Manual the point mass must have all its properties input by the user Mass X Y and Z coordinates If a Program Controlled point mass is used the mass and the horizontal position will be calculated from the panel elements in the structure i e excluding tubular stub lines and point buoyancy bodies The mass will equal the mass of water displaced and the horizontal position will be that of the center of buoyancy The moments of inertia or radii of gyration and vertical position Z cannot be determined by the program and must always be input Moments of inertia can be defined directly or by inputting radii of gyration If Define inertia values by is set to via Radius of Gyration you need to enter Kxx Kyy and Kzz If you select Direct input of Inertia you must enter the Ixx lyy and Izz values Tip After inserting your point masses solve for hydrostatics only
109. irection defined no Cross Swell This option will not be available if multiple structures are connected with a Connection Stiffness matrix If set to Yes and a Connection Stiffness object is then defined between two structures it will show as a yellow field In addition the Analysis Options item will be marked with the question mark until either the Connection Stiffness matrix is suppressed or is changed to connect between a point and a structure or the option is set to No Near field solution If Yes specifies that the near field solution should be used in the calculation of mean drift force By default the far field solution is used which only calculates the mean drift force in three horizontal degrees of freedom i e surge sway and yaw The far field solution is also unable to consider the hydrodynamic interaction between structures No Automatic Wave Drift Damping Calculation If Yes stops the automatic calculation of wave drift damping for a floating structure Note that the wave drift damping calculated by the program is only for the floating structure damping from risers etc is not included No Current Phase Shift If Yes switches off the wave phase shift due to a current speed No drift coefficients If Yes disables the Mean Wave Drift Force calculations No pressure post processing If Yes specifies that there will be no pressure post processing and therefore the connectivity warnings can be omitted No Yaw Wave Drift
110. is Actual Response Low Frequency The low frequency subtype values are obtained by filtering the actual response with a filter which has a cut off frequency of one third of the frequency of the 10 spectral line i e with N spectral lines n 0 1N 1 Wcutoff Wn 3 Wave Frequency the wave frequency response is that which remains when the low frequency re sponse is subtracted from the actual response RAO Based The RAO based motions are those that are calculated using only the RAOs ignoring the affects of connections unless these are included as additional matrices in the diffraction analysis using the applied wave These values are calculated at the center of gravity and are available in all translational and rotational component directions Plot availability Line graph presentation Distance Rotation plotted against Time Line Graph Input Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 81 Approach Use the Component input to select which position component to plot either X Y or Z for translation or RX RY or RZ for rotation Line Graph Output Maximum Value and Minimum Value of Structure Position and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box 2 8 2 2 2 Structure Velocity Result Desc
111. itor menu bar for more details Calculate Full QTF Matrix If Yes specifies calculation of the full QTF matrix Use Full QTF Matrix If Yes specifies that the full matrix of difference frequency QTFs is to be used when calculating slowly varying drift forces Use Sum Frequency QTFs If Yes specifies that the full matrix of sum frequency QTFs is to be used when calculating slowly varying drift forces in addition to using the full matrix of difference frequency QTFs You must also have Use Full QTF Matrix set to Yes to use this feature 2 6 4 Common Analysis Options The analysis settings available in this section of the Details panel control how the analysis is performed In normal circumstances they will not need adjusting however if you get modeling warnings then you may wish to turn on the Ignore modeling rule violations option Refer to the Aqwa Reference manual Help gt Aqwa Reference from the Aqwa Editor menu bar for more details Note Options appear based on the configuration of the analysis Not all of the options below will be visible for a particular Analysis Settings object Options are listed below in alphabetical order to make them easier to find Calculate C I F Using Added Mass and Damping If Yes calculates the Convolution Integral Function based on both added mass and damping The default method for calculation of the Convolution Integral Function uses the radiation damping only Calculate Motions Using R
112. lack The rules for defining fixed and movable structures are as follows 1 If neither of the two is connected to a fixed connection point the structure with the Connection Point on Structure A option will remain at its original position and the structure with the Connection Point on Structure B option will be moved 2 The Connection Point on Structure A or Connection Point on Structure B designations will be over ridden in some situations If one of two structures is connected to a fixed connection point or is part of a group of articulated structures that are already connected to a fixed connection point then that structure will remain in a defined position and the other structure will be moved If this second structure is also part of a group of articulated structures that are not connected to any fixed connection point the full group to which this structure is already connected will also be moved Note that this action is independent of the Connection Point on Structure A or Connection Point on Structure B designations 3 If one or both of the structures are part of groups of articulated structures and none of these structures is connected to a fixed connection point then rule 1 applies and the structure with the Connection Point on Structure B designation will be moved along with its group of structures 4 If both articulated groups are already connected to fixed connection points the new joint is then going to close the loop See ru
113. led You can then enter the number of elements Number of Elements to use in the analysis of the cable You must have Use Cable Dynamics set to Yes in the Hydrodynamic Time Response system s Analysis Settings in order to be able to use dynamics for an individual cable If Use Dynamics is set to No for a cable whose Connectivity is Connection Point amp Structure the Sea Bed Slope parameter is made available This value is the sea bed slope in degrees for this mooring line A positive slope is for the sea bed to slope up from the anchor towards the attachment point and a negative slope is for the sea bed to slope down from the anchor towards the attachment point Note that the slope is ignored if cable dynamics is being used for the solution Once the cable is fully defined the initial tensions at the start and end of the cable Initial Cable Tension Start Initial Cable Tension End are reported in the Details panel To avoid the iterative calculation of the mooring forces the program establishes a database covering all the expected configurations of the cable Additional controls enable fine control over the cable The availability depends upon if the cable is at tached between a fixed point and a structure or between two structures For cables attached between a fixed point and a structure Connectivity set to Fixed Point amp Structure the range of the possible end points of the cable is determined by Negative dZ measured from
114. les for Closed Loops p 34 below 2 4 5 2 Moving Structures Structures are moved in two steps They are first translated which causes the joint points to be coincident and then the structures are rotated so that the two sets of axes attached to the joint object become superimposed This gives you the freedom to set an initial orientation for the structures at the start of the Time History Analysis You will not see the structures move in the viewer The resulting set of axes defines the local joint axes at the start of the Time History Analysis In this set of axes some rotational motion of the structures will be allowed during the Time History Analysis de pending on the type of joint selected Ball and Socket Joint all rotations are allowed Universal Joint rotations are allowed around the X and Y axes of the local axes system Hinged Joint rotations are only allowed around the X axis of the local axes system Rigid Joint no rotation is allowed 2 4 5 3 Closed Loops In hydrodynamic analyses the following conditions apply to closed loops in articulated groups of structures Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 34 of ANSYS Inc and its subsidiaries and affiliates Define Connections The joint positions in the closed loop must be geometrically compatible It is not possible to connect two structures using two joints if the distance between these
115. line during the winch action will change as the length changes i e the stiffness during the simulation assuming that the length varies from L to the final length Lf will be EA L La to EA Lf La where EA KO L The speed entered is positive for paying out and negative for winding in In mathematical terms the speed is dL dt where L is the unstretched length of line and t is time For lines which have significant strain e this precludes steel which yields at about 0 001 the user may wish to consider the speed of the drum in terms of stretched length When winding in the line wound onto the drum will have the same tension as the free line itself at any particular time This means that in order to wind a length of unstretched line the effective speed must be increased by a factor of 1 e This is done automatically If the user wishes to simulate a stretched line speed for winding in then the speed specified should be input with a speed reduction factor of 1 1 where e is the average strain When paying out the adjustment of speed is not straightforward The elastic energy of the line on the drum will depend on exactly how the line was wound on the drum originally This energy stored on the drum is unknown and is assumed to be zero i e the line on the drum when paying out is assumed to be unstretched The effective winch speed effectively with only 1 side of the line stretched is 1 2 If the user wishes to simulate a
116. llowed around X axis Rigid Transmitting a moment about all three axes and not free to rotate at all This type of constraint enables you to find the reactions between two or more structures This type of joint rigidly connects the structures together so that the solution of the equations of motion is the same as if one structure was defined Figure 2 4 Rigid Joint In order to see the shape of the connections more easily you can switch to wireframe mode Connectivity Select the type of connectivity for the joint Fixed Point and Structure Structure and Structure Fixed Point For Connectivity of Fixed Point and Structure select the fixed point from a dropdown list of existing fixed points Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 32 of ANSYS Inc and its subsidiaries and affiliates Define Connections Connection Point on Structure A B Allows you to select the connection point on the contact struc ture s from a dropdown of existing connection points Stiffness About X Y Z These three fields define the rotational stiffness about the X Y and Z axes Damping About X Y Z These three fields define the rotational damping about the X Y and Z axes Translation Friction Coefficient Friction coefficient for transverse force k1 Rotational Coefficient Friction coefficient for overturning moment k2 Axial Friction Coef
117. ls Computation of the second order wave forces via the full quadratic transfer function matrices permits use over a wide range of water depths Aqwa Hydrodynamic Diffraction can also generate pressure and inertial loading for use in a structural analysis as part of the vessel hull design process The results from a diffraction analysis can be mapped onto an ANSYS Mechanical finite element model for further structural assessment and detailed design Since the mapping function automatically accounts for mesh differences between the hydrodynamic and finite element models they do not have to be topologically identical Aqwa Hydrodynamic Time Response provides dynamic analysis capabilities for undertaking global per formance assessment of floating structures in the time domain A wide range of physical connections such as mooring lines fenders and articulations are provided to model the restraining conditions on the vessels In addition sea keeping simulation may be undertaken with the inclusion of forward speed effects Slow drift effects and extreme wave conditions may be investigated and damage conditions such as line breakage may be included to study any transient effects that may occur Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 1 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential in
118. ms can be dragged from the Analysis Systems Toolbox to the Project Schematic to create your analysis See Create a Hydrodynamic Analysis System p 3 for more detailed information on creating your analysis using the Project Schematic File View Took Units Extensions Heb lad Project Bilimport lt pReconect Z Refresh Project Update Project E Analysis Systems Design Assessment amp Electric F A Y B Harmonic Response 2 Geometry F 20 oe Hydrodynamic Diffraction 3 Madal Hydrodynamic Time Resporee t Linear Buckling 4 ser 4 es sero 2 Magnetostatic 5 CE Solution P i 5 eS Solution 6 Results GB Modal 6 Results Hydrodynamic Diffraction Hydrodynamic Time Response hh lt ogi e ad 4 gt el eel G Modal Samcef ty Random Vibration GB Response Spectam G Rigid Dynamic atic Structural E Static Structural Samcef a Steady State Thermal E Thermal clectric GA Transient Structural Transient Thermal Y Vew Al Customize S Ready Ei Shaw Progress Show 4 Messages Many tasks in the Schematic can be performed using Context Menu Options that display when you right click on a cell in a Hydrodynamic system in the Project Schematic Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 91 Workbench Interface Figure
119. n duc galeava aabeovaaentia en aka Vaka ca Eais 43 2 7 Applying Ocean Environment and Forces ccccsssssescesseceseesenceecessesceseeseeseesesseneeseessneeeseeseeeesoess 46 2 7 Ve Structure Selection aa a soak easedecs ea a E be AY taal eee Buse ed teates 46 27 2 GRAVILY ntiiseesisreed Sleeved a S E aT E a ital wht E EE E aT aia 47 2 73 Wave Direction Saino aaen i aE EE EEE E AE EOE AE EEE AE EE O tivedays 47 2 7 4 Wav FreQUeNCleS aenieei eei nia aa E EA EEE EE EEA EE EER 47 PA eLA 0 E A E E A EEE 48 D790 ROUGE Wav eiii isoine ai eoeta eane EEEE ox nal A Ee a EE REE SEAN ot at EESE SET Olan oud aiia 49 277 Ae Ullah WAVE cast raa reese Eaa aasa aeae E AAAA AEAEE A RE S ATESA Maceo SEENEN a E Ea aE iS 50 2 7 7A JONSWAP Hor Alpha niisiis iaieineea enek iaie ia aiaei aeien 52 2 7 7 2 PIEFSON MOSKOWINZ sensin daeina aa A E adel a anode 52 DA ea GAUSSIAN a Ee E e cede EE E E E E E A E ER 52 2 774 User Spectra 1D aneientir e a E EEE Ei E See EARN EEE dude A ei 53 2 4 osUser TIME FISCOLY sins an aE a a a E A E EAE EES 53 2 7 8 lrfeg lar Wave GOUD ieisiecniee niiae ise ican oneal E AE E AE E E 56 QED CUNE e iin a oes A ea a a AAE a dew E EASE EE aa a E AE T A E Ka AEEA 56 DT KOANTA a TO EEEE EE E TE TOSE A E E EE E E EE TO cheateeeetams 58 2 7 10 1 Ochi ANd SHIN SPSCtrUM veres einernie tarana enS EEEE TRAE E E aE aae 60 2 7 10 2 APi Stahdard Spectrum sner en E E EE A A sii aE A a ai 60 2 7 10 3 NPD Standard Spectrum s rissen eene
120. nalysis right click on the Hydrodynamic Time History object then select Insert gt Wind gt wind type or click on the Hydrodynamic Time Response object and from the Analysis toolbar select Wind gt wind type The available wind types are Constant Velocity Time Dependent Velocity Ochi and Shin Spectrum e API Standard Spectrum e NPD Standard Spectrum ISO Standard Spectrum User Defined Spectrum The wind type of Constant Velocity is permitted for any wave type Enter the Speed and Direction of the constant wind in the Wind Spectral Definition section of the Details panel Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 58 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces Details of Wind Name Wind Visibility Visible Activity Not Suppressed gt Wind Spectral Definition w Spectra None Constant Speed O mjs Direction 0 The wind types Ochi amp Shin API NPD ISO and User Defined are only permitted for analysis types that permit irregular waves The following options are shown in the Details panel for all of the spectra except User Defined multiple sets of these options are defined for Time Dependent Velocity Enter the Refer ence Height at which the wind speed is measured the Speed of the wind at the reference height and the Direction of the wind spectrum Wind Spectral Definition wW Spectra Ochi
121. nd affiliates Establish Analysis Settings Output Full QTF Matrix If Yes writes an ASCII file AL QTF which can be used for external post processing The file is in fixed format as follows AQTF 1 0 EXAMPLE FULLY COUPLED SUMM DIFF QTF 14 3 0 00000 30 00000 45 00000 90 00000 0 3490659 0 4188791 0 5235988 1 4 2 3 1 4695E 03 4 8995E 05 7 4829E 03 1 0434E 07 2 9763E 01 2 1092E 04 5 0714E 03 3 1427E 03 2 0972E 03 3 4310E 04 5 3036E 02 2 4030E 01 1 3916E O1 1 1357E 06 1 2190E 03 8 1649E 06 6 3355E 01 1 9725E 04 1 0582E 01 7 0678E 05 1 2178E 03 4 6883E 06 1 0078E 00 7 8328E 03 etc Header Record 1 Columns 1 10 Reserved for Version Header AQTF 1 0 Columns 11 80 Run Title For each structure Logical Record 1 Columns 1 2 Structure Number Columns 3 4 Number of Directions for this structure Columns 5 6 Number of Frequencies for this structure Columns 9 80 6 Directions degrees PER LINE in field widths of 12 If more than 6 directions are input then columns 9 80 are used on the next line Logical Record 2 Columns 9 80 6 Frequencies radians sec PER LINE in field widths of 12 If more than 6 frequencies are input then columns 9 80 are used on the next line up to the total number of frequencies Next N N Logical Records N Number of frequencies These are 4 lines each where Line 1 Columns 1 2 Structure number Line 1 Columns 3 4 Direction number Line 1 Columns 5 6 Firs
122. ng Optional task that can be 1 In an analysis system schematic perform either of the geometry done before attaching following options geometry Right click on the Geometry cell and choose Proper ties OR Select the Geometry cell in the schematic for a stand ard analysis the from the Workspace toolbar drop down menu choose any option that includes Proper ties or Components Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 4 of ANSYS Inc and its subsidiaries and affiliates Attach Geometry Procedure Condition Procedural Steps 2 Check boxes to specify Default Geometry Options and Advanced Geometry Defaults Attaching DesignModel er geometry to a hydro dynamic sys tem DesignModeler is running in an analysis system Double click on the Model cell in the same analysis system schematic The Aqwa application opens and displays the geometry DesignModeler is not run ning Geometry is stored in an agdb file 1 Select the Geometry cell in an analysis system schematic 2 Browse to the agdb file from the following access points Right click on the Geometry cell in the Project Schematic Import Geometry and choose Browse Double click on the Model cell in the schematic The Aqwa application opens and displays the geometry Attaching CAD geo metry toa hydrodynam ic system CAD system is running Select the Geome
123. ng the positive X axis in the global coordinate system then values of X_REF Y_REF of 100 0 0 0 will indicate that the wave elevation was measured 100 metres downstream of the 0 0 wave reference point Omission of these data will default the reference point to 0 0 i e the wave elevation will be calculated using the origin of the global coordinate system as the point at which the wave elevation will be reproduced X_REF Y_REF and DIRECTION values appear in the Details panel for the Wave object The Spectrum Name will be used for graphs and tables where appropriate throughout the program and is appended to the Wave object name in the tree CURRENT SPEED and CURRENT DIRECTION are needed for calculation of the wavelengths of the wavelets used to reproduce the wave elevation If present they must match the correspond ing values in the unsuppressed Current object in the tree if there is no Current object an error will be generated If omitted it is assumed that there is no current and a warning will be issued The duration of the time history in the file should be at least 7200s This duration is necessary in order to give sufficient resolution of low frequency resonant responses If the file contains less data than this the data will be extended automatically up to 7200s using a process of mirroring and copying The maximum number of timesteps in the WHT file is 150000 Comments starting with in Column 1 may be added anywhere in the file
124. nsional frequency Note The wind profile for a user defined spectrum is assumed uniform in other words there is no modification to the wind speed with elevation The standard deviation s z is normally about 1 6th of the mean wind speed at a reference elevation of 10m i e the turbulence intensity I z is about 1 6th By definition the integral of S f F from zero to infinity is unity This is assumed in calculating the wind spectral energy density It is therefore UP TO THE USER TO SPECIFY A SPECTRUM COEFFICIENT depending on the formulation of the non dimensional spectrum In terms of the user defined parameters the spectral energy density is given by S F cs U f I z 2 Uz 2 F and f cf F z Uz The following examples choose all values to be at the reference elevation 10m for simplicity with a mean wind speed of 30 9m Example 1 Specifying the API Spectrum as a User defined Spectrum To specify the API spectrum as a user defined spectrum the user specifies Uz 30 9m s Mean wind speed z 10 0m Reference elevation cf 40 0 Frequency coefficient cs 1 0 Spectrum coefficient I z 0 1636 Turbulence intensity 0 15 2 0 125 and for each f U f f 1 1 5f 5 3 where f 40 0 10 0 30 9 F 12 945 F hertz The standard deviation will then be calculated as s z 0 1636 30 9 5 055 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential info
125. nts in the Matrix Definition Data window that appears below the model 2 3 8 Additional Added Mass Frequency Independent This object may be used to input frequency independent additional added mass in global directions using tabular input Only one definition of Additional Added Mass per structure can be active i e not suppressed for the analysis and the values are added to those calculated automatically during the analysis To add Additional Added Mass 1 Select a part in the Tree Outline 2 Right click on the part and select Add gt Additional Added Mass or Click on the Add icon in the toolbar and select Additional Added Mass from the dropdown list An Additional Added Mass object is added to the part 3 Select the Additional Added Mass object in the Tree Outline and enter the matrix coefficients in the Matrix Definition Data window that appears below the model 2 3 9 Current Force Coefficients This object may be used to include the viscous drag of the current on the hull of a fixed or floating structure using tabular input in the Current Force Coefficients window The term current force coefficient is used to differentiate these coefficients from traditional drag coefficients and from coefficients of wind force The current force coefficients are defined as the force or moment per unit velocity squared The moment is about the center of gravity of the structure These forces are a function of the relative velocity between
126. ond the capabilities of a linear analysis in which case inaccurate results can be produced The Result Type can be defined as Cyclic where an equivalent phase position of the incident wave component can be selected or is shown in the graph as the time as a proportion of wave period if a range is chosen Amplitude Maximum value of the selected result Minimum value of the selected result When Cyclic is selected Wave Position Phase can be set to 0 or t T 0 or 90 or t T or you can enter a specified phase position in rotation units or select a Range of results for animation If a range of results is selected then the Number of Steps can be selected The more steps the smoother the animation but the longer the results take to process If you select a range of results for animation after you evaluate the Pressures and Motions results right click on the object and select Evaluate All Results controls appear that allow you to start pause and stop the animation If a particular result is required from the animated set click on the graph to display it Other controls on the graph allow you to change the time over which the animation occurs and create an avi animation file Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 87 Approach File Edit View Units Help al StQQRMQ Insert Result Project
127. onnectivity for the fender Fender and Contact on Structures Fender On Structure Contact On Fixed Point Fender On Fixed Point Contact On Structure Type Fixed or Floating Note that Floating fenders cannot have a horizontal connection plane If there is more than a 60 degree angle between the Floating fender and contact plane directions a warning is generated saying that the forces are in error But this will not prevent the run from completing Action For a Fixed fender you can select Omni Directional or for either fender type choose the axis X Direction Only Y Direction Only or Z Direction Only for a uni directional fender Fender Connection Point Contact Connection Point Allows you to select an existing Connection Point on a structure to define the fender attachment point and contact plane origin These are present when the Fender Contact is on a structure Fender Fixed Point Contact Fixed Point Allows you to select from a dropdown list an existing Fixed Point for the Fender Contact when the connectivity is specified as such Damping Coefficient Material or structural damping coefficient 8 Damping is modelled as linear material damping where the damping coefficient is 8 x the stiffness Damping is only applied in the dir ection perpendicular to the contact points e Friction Coefficient This is the friction coefficient u The friction force is given by F pR where R is the normal reaction The
128. ontrolled Number of Spectral Lines Definiti User Defined Number Of Spectral Lines 60 Omit Calculation of Drift Forces No Start and Finish Frequency Defi Program Controlled Start Frequency 0 322109013795853 rad s Finish Frequency 2 83794689178467 rad s Significant Wave Height 2m Zero Crossing Penod 8s Cross Swell Details Cross Swell Spectrum None An irregular wave can be added to the Hydrodynamic Time Response system either individually or as part of an Irregular Wave Group In addition it can be added to the Hydrodynamic Diffraction system when Linearized Morison Drag p 44 is specified for the analysis only a single irregular wave can be used in the Hydrodynamic Diffraction system and no Cross Swell should be specified Note Although you can add multiple irregular wave groups and individual irregular waves to your analysis you must have only one active in order for the analysis to solve the others must be suppressed To insert an irregular wave right click on the Hydrodynamic Time Response or Hydrodynamic Dif fraction object and select Insert gt Irregular Wave gt wave type or select Irregular Wave gt wave type from the Analysis toolbar The available wave types are listed below The following parameters are available in the Details panel for all irregular wave types Direction of Spectrum is the direction of waves within a wave spectrum Seed Definition defines the random seed for a wave spectrum Th
129. or more details The non dimensional wind spectrum S f is given by e for 0 000 lt f lt 0 003 S f 583 f 2 0 003 e for 0 003 lt f lt 0 100 S f 420 f 7 1 35 11 5 e for 0 100 lt f S f 838 f 1 f 35 11 5 We note that the peak occurs at approximately f 0 0117 where S f 2 0685 At f 1 0 S f is approxim ately 14 of the peak value where f Non dimensional frequency F z Uz S f Non dimensional wind spectrum F S F Ux 2 F Frequency in hertz z Elevation Uz Wind speed at elevation z S F Wind speed energy density Ux Shear velocity The wind speed elevation z and the shear velocity are given by Uz U10 2 5 Ux In 0 1 z Ux U10 sqrt C10 C10 0 000794 0 00006658 U10 where U10 Wind speed at reference elevation of 10 metres 2 7 10 2 API Standard Spectrum The API wind spectrum is a simple non dimensional one as defined below Note that in later versions of API standards the recommended spectrum is the NPD spectrum Mean Profile The mean profile for the wind speed averaged over 1 hour at elevation z Uz can be approximated by Uz U10 z zr 0 125 where U10 Wind speed averaged over 1 hour at reference elevation of 10 metres Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 60 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces zr 10 metres Gust Fa
130. orce or Tension plotted against Time Line Graph Input For Whole Cable Forces use the Component input to select which Cable Force component to plot either X Y or Z force components or Anchor Uplift Tension or Laid Length Use the Connection field to select which cable s characteristics to plot e For Cable Section Tension use the Connection field to select which catenary cable s characteristics to plot Use the Cable Section field to select the Catenary Section for which you want to plot section tension Line Graph Output Maximum Value and Minimum Value of Cable Force Tension and the Time at which they occur Pos ition of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box 2 8 2 2 8 Time Step Error The error expressed as a percentage is graphed for each time step The program outputs the expected maximum error at each time step in each degree of freedom which is related to the chosen time step These errors can always be reduced by shortening the time step Result Description 2D graphs to illustrate the maximum error per step during the analysis Plot availability Line graph presentation Maximum Error Percentage plotted against Time Line Graph Input None Line Graph Output Maximum Value and Minimum Value of Maximum Percentage of Error and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting th
131. outside the range at which the hydrodynamic parameters are defined the program will automatically extrapolate the values required The effects of cross swell are implemented in most of Aqwa Select the Cross Swell Spectrum type in the Cross Swell Details section of the Details panel The Cross Swell Spectrum can be different from the current Wave Type However the parameters used to define the Cross Swell Spectrum are the same as those for the corresponding spectrum Wave Type except that the start and finish frequencies are calculated by the program For all wave types except User Time History and User Spectra 1D set Wave Range Defined by to either Period or Frequency Next set Start and Finish Frequency Period Definition The available options are Program Controlled both Start Frequency Period and Finish Frequency Period default Start Frequency Period User Defined Finish Frequency Period Program Controlled Finish Frequency Period User Defined Start Frequency Period Program Controlled User Defined both Start Frequency Period and Finish Frequency Period Start Frequency Period is the lowest frequency or longest period at which the spectrum is defined and Finish Frequency Period is the highest frequency or shortest period at which the spectrum is defined Enter values in the fields that are user defined based on the Start and Finish Frequency Period Definition setting Other parameters are available in the Details panel ba
132. point to the first pulley then if it exists to the second pulley and then to the cable end point Along with the pulley position defined by Connection Point which can be selected from the dropdown list of existing connection points you must enter a Friction Coefficient for the pulley The friction of the pulley is represented by T2 T1 where T2 is the larger tension and T1 the smaller T2 T1 is defined for the situation where the line turns through 180 around the pulley Within the program a friction factor y is calculated such that T2 T1 e The friction is then varied depending on how far around the pulley the line passes T2 T1 must be in the range 1 lt T2 T1 lt 2 with 1 being no friction 2 4 1 2 Non Linear Polynomial For Non Linear Polynomial cables enter the polynomial coefficients Coefficient A Coefficient B Coefficient C Coefficient D Coefficient E and Unstretched Length of the cable The coefficients of the polynomial define the force in the cable as a function of extension thus Force P1 E P2 E P3 E P4 E P5 E Where P1 P2 P3 P4 P5 polynomial coefficients E Extension of the mooring line as defined in the linear cable section 2 4 1 3 Non Linear Steel Wire For Non Linear Steel Wire cables enter the Asymptotic Stiffness and Asymptotic Offset in addition to the Unstretched Length of the cable These constants are physical properties used in defining the tension extension curve of a
133. r Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 80 of ANSYS Inc and its subsidiaries and affiliates Solution Surface Graph Input Use the Component input to select which force component to plot either X Y or Z for forces or RX RY or RZ for moments Surface Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the Frequency and Direction or Frequency and Position or Position and Direction at which they occur Position of Min in X Position of Max in X and Position of Min in Y Position of Max in Y These values can be parameterized by selecting the adjacent check box 2 8 2 2 Hydrodynamic Time Response Results Under the Solution object of a Hydrodynamic Time Response system a number of graphs will be available to track the behavior of number of parameters over time The graphs are all line graphs and the following categories of graphs are available 2 8 2 2 1 Structure Position 2 8 2 2 2 Structure Velocity 2 8 2 2 3 Structure Acceleration 2 8 2 2 4 Structure Forces 2 8 2 2 5 Fender Forces 2 8 2 2 6 Joint Forces 2 8 2 2 7 Cable Forces 2 8 2 2 8 Time Step Error 2 8 2 2 1 Structure Position Result Description 2D graphs to illustrate the following response subtypes of the Structure Position during the analys
134. rectory AQWA2NEUT pl p2 where p1 Aqwa database name without extension p2 Aqwa structure number optional defaults to 1 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 105 Appendix A file called p1_p2 ahd will be generated This file can be opened in a text editor if required Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 106 of ANSYS Inc and its subsidiaries and affiliates Index A aqwa attach geometry 4 create analysis system 3 attaching geometry 4 G geometry attach aqwa 4 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 107 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 108 of ANSYS Inc and its subsidiaries and affiliates
135. ription 2D graphs to illustrate the following response subtypes of the Structure Velocity during the analysis e Actual Response Low Frequency The low frequency subtype values are obtained by filtering the actual response with a filter which has a cut off frequency of one third of the frequency of the 10 spectral line i e with N spectral lines n 0 1N 1 Wcutoff Wn 3 e Wave Frequency the wave frequency response is that which remains when the low frequency re sponse is subtracted from the actual response RAO Based The RAO based motions are those that are calculated using only the RAOs ignoring the affects of connections unless these are included as additional matrices in the diffraction analysis using the applied wave These values are calculated at the center of gravity and are available in all translational and rotational component directions Plot availability e Line graph presentation Velocity plotted against Time Line Graph Input Use the Component input to select which Velocity component to plot either X Y or Z for translational velocity or RX RY or RZ for rotational velocity Line Graph Output Maximum Value and Minimum Value of Structure Velocity and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box 2 8 2 2 3 Structure Acceleration Result Description 2D graphs to illustrate the following response
136. rmal Y and Normal Z component values The default values of the added mass and viscous drag coefficients can be modified if desired Note Drag is not used in hydrodynamic diffraction analyses 2 3 6 Additional Hydrodynamic Stiffness This object may be used to input an additional linear hydrostatic stiffness matrix using tabular input in the Matrix Definition Data window The linear stiffness matrix relates to the hydrostatic forces contrib uting to the equations of static equilibrium of a structure Specifically the net linear hydrostatic forces F s acting at the center of gravity of a structure when the structure is at an arbitrary position X are given by F s K dK X e X Ble e K stiffness matrix e dK additional hydrodynamic stiffness matrix input in this object e X e equilibrium position B e buoyancy force at equilibrium If additional hydrodynamic stiffness is used it should be checked that the above expression which is used to calculate the linear hydrostatic forces throughout the Aqwa suite produces the forces on the structure intended by the user Note In this context hydrostatic forces can act in all 6 degrees of freedom In the equation above the term X e is the diffraction analysis defined position If the initial position in a subsequent motions analysis is not as defined in the diffraction run then there will be restoring forces which will try to return the structure to
137. rmation 64 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces Example 2 Specifying the Ochi and Shin Spectrum as a User defined Spectrum In order to input an Ochi amp Shin spectrum as a user defined spectrum we consider the definition of the Ochi amp Shin spectrum i e S F S f Ux 2 F f F Z Uz Although cf is unity S f is defined differently for the Ochi amp Shin spectrum and is only defined at the standard reference height of 10m Noting that the integral of S f F for the Ochi and Shin Spectrum is approximately 9 24 giving cs 1 0 9 24 0 1082 we can calculate the standard deviation s z as s z Ux sqrt 9 24 3 04 Ux The turbulence intensity is therefore I z 3 04 Ux Uz Noting that C10 0 000794 0 00006658 U10 and Ux Uz sqrt C10 Ux 30 9 sqrt 0 000794 0 00006658 30 9 1 650 This gives a turbulence intensity of I z 3 04 1 65 30 9 0 1623 We therefore specify Uz 30 9m s Mean wind speed z 10 0m Reference elevation cf 40 0 Frequency coefficient cs 0 1082 Spectrum coefficient I z 0 1623 and for each f U f is f 0 000 0 003 583 f 2 0 003 f 0 003 0 100 420 f 7 1 f 35 11 5 f 0 100 0 324 838 f 1 f 35 11 5 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 65
138. rmation as discussed above 2 4 4 Fenders Fenders are a type of mooring allowing the user to model material contact between two structures They are the only way to model contact so if there are no fenders structures can pass through each other From a practical point of view like other mooring elements fenders are defined as acting between two structures or one structure and a fixed connection point Depending on the relative positions of the structure on the type of Fender floating fixed unidirectional fixed omnidirectional and on their positions on the structures they create a varying force acting on the structure and added to the other forces used for computing the structures motions These forces are calculated using the properties defined for each fender A Contact Plane is defined for each fender this is the plane which the fender is going to impact This plane is defined by a point and a vector An attachment point is defined for each fender For fixed fenders this is the point where the fender is located on the structure For floating fenders the attachment point is translated to the mean water surface Fixed unidirectional and floating fenders also have a direction of action represented by a normal vector Along with the attachment point given in the fender s definition it defines a plane which is going to be the second plane pressing on the fender For floating fenders the actual attachment point is obtained by tr
139. ry cables Prior to Release 15 0 these objects were labeled as Connection Point 2 3 Define Parts Behavior A part is a group of geometric entities that form a ship or other structure that is to be analyzed in Aqwa The name is read in from the geometry database and the graphical view will show the part the appro priate structure will be highlighted when the part in the tree is selected Each part will be assigned a structure number for the analysis The parts can be included or excluded from the analysis using the Structure Selection A number of options can be set for each part in the Details panel Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 7 Approach To help visualization it is possible to show or hide specific parts using the Part Visibility option The Part Activity option is used to decide what structures are used in the analysis Note If a part is suppressed it cannot be used in the analysis However when a part is unsup pressed it must be added to the Structure Selection in order for it to be included in the analysis Total Structural Mass and X Y and Z Positions of COG the Center of Gravity are displayed for each Part This information is based on the masses defined for each element body of the structure Point Masses and Tubes Stubs It is important to remember that the mass of each
140. s warranties disclaimers limitations of liability and remedies and other provisions The software products and documentation may be used disclosed transferred or copied only in accordance with the terms and conditions of that software license agreement ANSYS Inc is certified to ISO 9001 2008 U S Government Rights For U S Government users except as specifically granted by the ANSYS Inc software license agreement the use duplication or disclosure by the United States Government is subject to restrictions stated in the ANSYS Inc software license agreement and FAR 12 212 for non DOD licenses Third Party Software See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software and third party software If you are unable to access the Legal Notice please contact ANSYS Inc Published in the U S A Table of Contents 1 Introduction What is Aqwa i eicsi cc3 t05 sete helena fleas saddbtaca eer caiane tevh endo dteaatbe tease saned tan beGieatsaee aatbeveatese 1 2 Approach neen Besser a a a nee el etd Bad aaa ced A laos cad lad Se a ee 3 2 1 Import or Create Hydrodynamic Analysis Systems scceeessseceessneeeceesseeeceesaeeesesseeeceessaeeeseesaaees 3 2 1 1 Import a Hydrodynamic System Database 4 scdssesisasesvnevcassanavectvanes esses ntovsssasubasvynseraddvenardages sas 3 2 1 2 Create a Hydrodynamic Analysis System siissiscaniuincsssvieniies sicdayncasutpan
141. s are also presented in global directions Within the geometry you can select the types of bodies that will be attached Once attached the diffracting behavior of surface geometry can be selected lines can be set to be Tu bular TUBE Elements or Slender Tube STUB elements and additional Aqwa specific objects can be added such as Point Mass Point Buoyancy and Disc The Details panel provides you with options for setting up the sea geometry s Water Depth and size Water Size X Water Size Y which can be used to alter the graphical view By Slicing on the XY plane Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 6 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior the sea level coincides with the point where the surface geometry is split to form above water non diffracting and below water diffracting sections By default this setting in the Surface Body Details view will be Program Controlled and determined from the water level however you can manually override it to define specific bodies to be non diffracting It is important that the correct water depth is specified especially with shallow water conditions since the sea bed acts as a boundary condition to the diffraction analysis The Water Size in the X and Y dir ections modifies the extent of the graphical display of the water surface and sea bed The Water Density can also be changed
142. same way as a normal user defined spectrum As the phases of the spectral wavelets are allocated randomly the input wave elevation time history will not be reproduced Note Current is ignored when calculating the phase wave forces on the structure and the wave kinematics for Morison elements The WHT file is an ASCII file with the wave elevation data in free format with 2 values per line The first value is the time and the second value is the wave elevation The following 2 statements are required in the file DEPTH value G value The DEPTH value must be the same as the Water Depth specified in the Geometry Details or else an error will be generated The G value is compared to the Gravity specified in the Gravity object Details to determine the units used The following optional data can also be input If any are omitted the relevant value defaults to zero DIRECTION value degrees X_REF value Y_REF value NAME Spectrum Name Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 54 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces CURRENT_SPEED value CURRENT_DIRECTION value degrees Note The X_REF and Y_REF values are used in the calculation of the phase of the wave and are the position where the wave elevation was measured For example in SI units if the DIRECTION of the wave is zero degrees in other words alo
143. sed on the wave type defined The following wave types are available 2 7 7 1 JONSWAP Hs or Alpha 2 7 7 2 Pierson Moskowitz 2 7 7 3 Gaussian 2 7 7 4 User Spectra 1D 2 7 7 5 User Time History Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 51 Approach 2 7 7 1 JONSWAP H or Alpha The JONSWAP wave spectrum can be used to describe a wave system where there is an imbalance of energy flow i e sea not fully developed This is nearly always the case when there is a high wind speed It may be considered as having a higher peak spectral value than the Pierson Moskowitz spectrum but is narrower away from the peak in order to maintain the energy balance If you choose JONSWAP Hs as the Wave Type Significant Wave Height will be used in the calculations rather than the parameter Alpha which is used when the Wave Type is set to JONSWAP Alpha Parameterization of the classic form of the JONSWAP spectrum with parameters of fetch and wind speed was undertaken by Houmb and Overvik BOSS Trondheim 1976 Vol 1 These empirical parameters which you must enter are termed Gamma 7 Alpha a and Peak Frequency wp the frequency at which the spectral energy is a maximum The peak frequency together with empirical parameters termed Gamma and Alpha are used in this formulation The spectral ordinate S at a frequency w is
144. sis you may click on the field next to Structures to Exclude then click Apply with no structures selected The Aqwa solver requires that a group of interacting structures be consecutively ordered for the analysis Set the structure ordering so that all structures in a particular interacting group are listed sequentially For example if you have 4 structures named A B C and D structure C is excluded and structures A and D are in an interacting group you must list structures A and D sequentially in the Structure Ordering section of the Details panel In this case the order could be A D B or B D A but it could not be A B D There are some limitations on the number of interacting structures and the total number of structures There is a maximum number of 20 interacting structures in any group Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 46 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces e The total number of structures must be less than or equal to 50 The number of added mass sub matrices must be less than or equal to 430 This is calculated by summing the squares of the number of structures in each group and adding to that the number of non interacting structures Note Suppressing unsuppressing a structure from the right click menu on the tree or the Details panel of the structure affects the structure s
145. sressssteessssteesseteesssreessssreesssete 103 6 2 Transferring Pressures and Motions Frequency Domain to Mechanical Models sses 105 VOX esac saves PAE deste E can ooodtwnsectad ethos SE TO Cidade E E cat tostiaettes EAE E catverei asia 107 Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates v vi Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates Chapter 1 Aqwa Introduction What is Aqwa ANSYS Aqwa provides an engineering toolset for the investigation of the effects of wave wind and current on floating and fixed offshore and marine structures including spars floating production storage and offloading FPSO systems semi submersibles tension leg platforms TLPs ships renewable energy systems and breakwater design Aqwa Hydrodynamic Diffraction provides an integrated environment for developing the primary hydro dynamic parameters required for undertaking complex motions and response analyses Three dimen sional linear radiation and diffraction analysis may be undertaken with multiple bodies taking full account of hydrodynamic interaction effects that occur between bodies While primarily designed for floating structures fixed bodies such as breakwaters or gravity based structures may be included in the mode
146. status in the Structure Selection If you suppress a structure and then unsuppress it you must go to the Structure Selection object and remove it from the excluded structures set in order for it to be included in the analysis 2 7 2 Gravity This tree object enables the definition of Gravity for this analysis changes can be made if you want to try to match another analysis 2 7 3 Wave Directions The Wave Directions tree object enables the definition of a range or single wave direction to use in the analysis If Type is set to Single Direction Forward Speed you can enter a structure Forward Speed and a Wave Direction In this case only a single wave direction can be analyzed If Type is set to Range of Directions No Forward Speed waves are automatically created in 180 and 180 directions and either the Interval or the number of intermediate directions No of Intermediate Directions can be specified If a direction range is of particular interest additional ranges or specific directions can be added To add Optional Wave Directions select Single or Range from the Additional Range dropdown For the Single direction specify the Start Angle For a Range of directions specify the Start Angle End Angle and either the Interval or No of Intermediate Directions Duplicated directions will automatically be removed although the number of directions does not con tribute greatly to the analysis time there is a limit imposed of a total
147. sults The Time History Motion results object allows you to view an animation of the motion of the parts in your project over the entire analysis period You can insert the Time History Motion object in the tree either before or after running the analysis Only one Time History Motion result can be added to an analysis Controls below the Geometry window allow you to start and pause the animation change the portion of the animation that plays and create an AVI movie file Fie Edt View Unts Hep J F tf St QaQagRQQtam rye SBE ua 200 08 mn Description Play the animation from the current time Pause the animation Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 89 Approach Control Description Current Time a slider to the Enter the time at which to start the animation for viewing or video right of the field can be used in export Start the video export Enter the time at which to end the video export will change Video Length accordingly Enter the number of seconds of animation that you want to export will change Video Stops At accordingly To export a video of all or part of an animation set the Current Time and either Video Stops At or Video Length Then click the video export icon A dialog box will appear asking you to provide a file name and browse to the location where you w
148. t Frequency number Line 1 Columns 7 8 Second frequency number Line 1 Columns 9 80 Real part of difference frequency QTF for 6 d o f PD Line 2 Columns 9 80 Imaginary part of difference frequency QTF for 6 d o f QD Line 3 Columns 9 80 Real part of sum frequency QTF for 6 d o f PS Line 4 Columns 9 80 Imaginary part of sum frequency QTF for 6 d o f QS Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 41 Approach Note that the QTF coefficients normally referred to as P real and Q imaginary are in standard format If i is the 1st frequency and j is the second then P i j coefficients are symmetric and Qii j coefficients are anti symmetric i e P i j P j i and Q i j Q j i The force time history is therefore given by F FD cos w2 w1 t P1 FS cos w1 w2 t P2 Where FD SQRT PD 2 QD 2 FS SQRT PS 2 QS 2 w1 1st frequency w2 2nd frequency P1 ATAN2 QD PD P2 ATAN2 QS PS Do not output LIS banner page If Yes disables printing of the banner page in the LTS file No data list If Yes disables all extended data output in the LTS file Output Element Properties If Yes writes complete details of each element used in the body modeling to the LIS file All important details of the body elements are output together with the resul
149. t is set up and behaves in a manner similar to the Workbench Mesh object However for the Aqwa Mesh object some fields in the Details panel have a Program Con trolled option that will set related fields to default values If you instead select User Defined you may set the related field values yourself This behavior is different from that described for the Workbench Mesh object in the Meshing User s Guide 2 5 2 1 Mesh Parameters The Meshing Type option controls the algorithm that is used for the mesh generation The default is for it to be Program Controlled in which case the Surface Only Meshing algorithm is used for parts that only contain surfaces and the Combined Meshing is used if the part also includes lines If the Program Controlled option fails to produce a satisfactory mesh then you may control the selection manually 2 5 2 2 Sizing Aqwa allows you to control the sizing of the elements in the mesh as described in Sizing Group in the Meshing User s Guide 2 5 2 3 Inflation Aqwa allows you to control the inflation of the elements in the mesh as described in Inflation Group in the Meshing User s Guide On surfaces inflation requires a Mesh Local Inflation Control object to be created in order to specify which face of the model is going to be targeted by the inflation process and from which boundary it is going to start The Mesh Local Inflation Control object allows the user to select these sections of the geometry
150. tant properties of the bodies Output Source Strengths If Yes writes the singularity strengths for both the modified and unmodified values to the LTS file the modified strengths being a linear combination of the unmodified values The actual relationship is a function of the number of body symmetries that are used Output Potentials If Yes writes the modified and unmodified values of the potential at the diffraction element centers and at the field points to the LIS file This information may be used to define the fluid flow field about the body Output Centroid Pressures If Yes writes the total hydrostatic and hydrodynamic fluid pressures at each plate in the model to the LIS file No Statistics If Yes stops the automatic calculation of statistics at the end of each simulation run Statistical processing can be lengthy for long simulations This option can be used to reduce processing time if statistics are not required No wave elevation at field points If Yes disables the writing of field point wave elevation in the LIS file Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 42 of ANSYS Inc and its subsidiaries and affiliates Establish Analysis Settings 2 6 3 QTF Options The analysis settings available in this section of the Details panel control the QTF output refer to the Aqwa Reference manual Help gt Aqwa Reference from the Aqwa Ed
151. the frequency range of the fitted spectrum and subject to the limitations of roundoff error This is achieved by multiplying each of the spectral wavelets by a different Low Frequency Perturbation LFP Function i e Wave elevation Sigma j 1 N a j cos w j t k j x i j LFP j t Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 53 Approach where N number of spectral lines set to 200 j wavelet number t time w frequency as normally output by the Aqwa solver phase as normally output by the Aqwa solver a j amplitude k wave number Note that no spurious low frequency waves are generated by the above method For any wavelet the minimum frequency present in the wave elevation is w j dw where dw is the highest frequency present in the LFP function Note also that there is no frequency overlap for each wavelet Each LFP function can be considered as a frequency spreading function over a limited set of contiguous frequency bands In this case each wavelet has a different energy as opposed to the standard Aqwa wavelets which have equal energy Import of the time series will also generate a user defined spectrum using a Fast Fourier Transform whose frequency range is based on a JONSWAP fit of the wave elevation spectral density If drift effects are ignored this spectrum will be used in the
152. the model at the mesh level in order to generate a better mesh The local pinching control fields are set similarly as those described in Changing Pinch Controls Locally in the Meshing User s Guide 2 5 3 3 Inflation Control Adding a Mesh Local Inflation Control object allows you to control the inflation of the elements at specific boundaries in the mesh using fields similar to those described in Notes on Defining Local Inflation Controls 2D Only near the bottom of the section Inflation Control in the Meshing User s Guide You can use the global inflation settings or if Use Global Inflation Parameters is set to No you can set local values for the fields that are displayed 2 6 Establish Analysis Settings The Analysis Settings object allows you to specify how the analysis runs and how the results are shown Different fields appear in the Details view for the object depending on the parent object Hydrodynamic Diffraction or Hydrodynamic Time Response The Sea Grid Size Factor controls how much larger the sea area is than the structure or structure group if there are interacting structures present The default value of 2 will cause the sea area to be twice as long as the structure in the X or Y directions a ratio of X 1 6 Y is maintained This field is only displayed for the Hydrodynamic Diffraction system The following sections appear in the Details view for the Analysis Options object 2 6 1 Time Response Options 2 6 2 Output Fil
153. then the hydrostatic results will be available and the values of mass will be calculated before performing the full Aqwa analysis 2 3 4 Point Buoyancy Point buoyancy PBOY elements can be inserted into the model these require a position X Y Z and a Volume 2 3 5 Disc Disc elements can be used to create an area that has drag Viscous Drag Coef and added mass Added Mass Coef in the direction perpendicular to the disc The Diameter of the disc is required along with the centroid and the definition of the normal direction If the centroid is at the position of an existing vertex set Centroid Definition to Select Vertex and click Pick in the Vertex field then select the vertex on the model and click Apply To enter the coordinates of the vertex directly set Centroid Definition to Specify Coordinates and enter the X Y and Z values You can specify the normal by picking a second vertex or specifying the direction of a normal vector To use an existing vertex to define the normal set Normal Definition to Select Second Vertex and click on Pick in the Normal Vertex field then select the vertex on the model and click Apply To enter the Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 12 of ANSYS Inc and its subsidiaries and affiliates Define Parts Behavior vector for the normal directly set Normal Definition to Specify Vector Components and enter the Normal X No
154. they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 76 of ANSYS Inc and its subsidiaries and affiliates Solution 2 8 2 1 4 Steady Drift Result Description 2D or 3D graphs to illustrate the mean drift forces moments applied on the structure and how they change with direction frequency or both direction and frequency Plot availability Line graph presentation Force Moment plotted against either Direction or Frequency Surface graph presentation Force Moment plotted against Direction Frequency The Frequency Scale can be modified to be Period Scale if required Line Graph Input e Use the Component input to select which force component to plot either X Y or Z for forces or RX RY or RZ for moments e When the plot is performed against Direction then the required frequency can be chosen using the Fre quency input e When the plot is performed against frequency then the required direction can be chosen using the Dir ection input Line Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the first Frequency or Direction at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Surface Graph Input Use the Component input to sele
155. tion Vertex Vertex Defining the XY Plane For For an Alignment Method of Vertex Selection select the Origin Vertex of the fender or contact plane a vertex defining the X direction X Direction Vertex and a vertex that would along with the other two vertices define the XY Plane Vertex Defining the XY Plane As these vertices must be part of a body in the geometry the user may have to anticipate and include for instance a dummy massless line body in the geometry oriented the same way as the fender to be defined In DesignModeler you can for example create such a line body as being perpendicular to the surface of the hull Rotation about Global Z Rotation about Local Y Rotation about Local X For an Alignment Method of Direction Entry define the alignment using these three rotation fields Note The Fender Axis definition should point towards the contact surface i e through the fender itself The Contact Axis definition should point towards the fender attachment surface i e opposite direction to the Fender Axis definition 2 4 4 1 Examples of Use of Fenders The following images show examples of using omni and uni directional fenders with various alignment methods Omni Directional Fender Details of Fender 1 Name Fender 1 Visibility Visible Activity Not Suppressed Connectivity Fender And Contact On Structures Type Fixed Action Omni Directional Fender Connection Point Connect
156. tions 2 5 1 Basic Global Mesh Options 2 5 2 Advanced Global Mesh Options 2 5 3 Local Mesh Controls 2 5 1 Basic Global Mesh Options If Global Control is set to Basic a limited number of meshing options are available in the Details panel The mesh is automatically generated on the bodies in the model its density is based on the defeaturing tolerance and maximum element size parameters The Defeaturing Tolerance controls how small details are treated by the mesh If the detail is smaller than this tolerance then a single element may span over it otherwise the mesh size will be reduced in this area to ensure that the feature is meshed The defeaturing tolerance can not be greater than 0 6 x max element size Max Element Size controls the maximum size of the element that will be generated In Aqwa this is explicitly related to the maximum wave frequency that can be utilized in the diffraction analysis If a particular maximum wave frequency is desired then this can be specified instead Max Allowed Fre quency and the associated maximum element size will be computed If a smaller element size is required for a particular part or body then one or many Mesh Sizing object s can be added to refine the mesh The Meshing Type option controls the algorithm that is used for the mesh generation The default is for it to be Program Controlled in which case the Surface Only Meshing algorithm is used for parts that only contain surfaces and the
157. try cell in an analysis system schematic Right click on the Geometry cell listed there Double click on the Model cell in the same analysis sys tem schematic The Aqwa application opens and displays the geometry If required set geometry options in the Aqwa application by highlighting the Geometry object and choosing set tings under Preferences in the Details view CAD system is not run ning Geometry is stored in a native CAD system file or in a CAD neutral file such as Parasolid or IGES CAD Interface Terminology Select the Geometry cell in an analysis system schematic Browse to the CAD file from the following access points Right click on the Geometry cell in the Project Schematic and choose Import Geometry Double click on the Model cell in the Project Schematic The Aqwa application opens and displays the geometry The CAD interfaces can be run in either plug in mode or in reader mode Attaching geometry in plug in mode requires that the CAD system be running Attaching geometry in reader mode does not require that the CAD system be running 2 2 1 General Modeling Requirements DesignModeler is the ANSYS tool used to create geometry for hydrodynamic systems For information on importing geometry created in DesignModeler see the Geometry section When using DesignModeler Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS
158. ue that is between 0 and the water depth A 0 degree direction defines the current flowing in the positive X direction 90 degrees defines it flowing in the positive Y direction This value will be used for the full depth as defined by Water Depth in the Geometry object q Current Definition Data Details of Current Depth mm Velocity m s Direction Name Current Visibility Visible Activity Not Suppressed For a variable current enter multiple rows containing information for the current Velocity and Direction at each Depth Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 56 of ANSYS Inc and its subsidiaries and affiliates Applying Ocean Environment and Forces Current Definition Data Details of Current Depth m velocity m s Direction Name Current Visibility Visible Activity Not Suppressed Depth is measured from the sea surface Depth values must be positive numbers and less than the depth of water If a complete definition of current with depth is not defined between the water surface and depth of water constant values will be assumed based upon the lowest and highest defined data So in the example above and assuming a water depth of 250m the current values at a depth of 0 the water surface will be a velocity of 2 5 m s and a direction of 45 degrees and at the sea bed the velocity will be 0 If there are multiple rows
159. ulated by the program based on the relative flow velocity at the bilge Keulegan Carpenter number roll natural frequency of the vessel and the radius of the bilge The roll damping coefficient used in the nonlinear roll damping force calculation is also calculated by the program based on a database stored within the program To compute the effects of nonlinear roll damping select Included in Calculations from the Non Linear Roll Damping drop down menu By default these are excluded from the calculations If selected addi tional parameters need to be provided It is assumed that the two bilges have symmetric properties about the center line of the vessel The Bilge Radius defines the local radius of the bilge corner dimen sion from the hull to the extreme of the bilge The Depth to Bilge is the vertical position of the bilge corner on the vessel in the global axis system The Offset of Bilge from Central Line is the lateral offset of the bilge corner from the center line of the vessel in the global axis system The central line is defined by selecting vertices from the geometry for the start and end points of the central line Reference Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 9 Approach Vertex for Start of Central Line Reference Vertex for End of Central Line For each end of the central line you can also specify X and Y of
160. ures common to all of the Aqwa analysis systems The following are discussed in this chapter 4 1 Generating Reports 4 2 Parameters 4 3 Comments Images and Figures 4 1 Generating Reports You can click on the Report Preview tab in the main window pane to generate a summary of all of the objects in your Outline Once started the report generation process must run to completion Avoid clicking anywhere in the Workbench window while the report is generating because it will stop the report and may cause an error The Details information for each object appears as tables in the report Figures and images appear as specified in the Outline Charts that appear in the outline are also included When you are viewing the Report Preview tab several related buttons will appear in your toolbar Use the Print button to print a copy of the report The Publish button will save the report in one of three formats mht a web page archive format that can be opened by Internet Explorer 5 5 or later e html file with graphics in a sub directory e html file with graphics in the same directory Click Publish then select the format in which you want to save from the Save as type drop down list Use the Send To button to send the report to an email recipient mht file format only Word or PowerPoint The document is opened in Word as any published HTML file would be Only the images contained in the report are imported in PowerPoint no other in
161. used of 600 points which is formed by the multiplication of Number of Vertical Partitions and Number of X Coordinates For cables attached between two structures the database uses a radial coordinate system in which Number of X Coordinates becomes the number of radial distances and the Number of Vertical Parti tions is the number of angular positions determined by maximum tension AY Maximum radial gt ao distance 2 4 2 Catenary Data Under the Connections object in the tree a Catenary Data object is automatically added Under this object you can insert definitions for various types of Catenary Sections and Catenary Joints that can be used to create Catenary Cables 2 4 2 1 Catenary Section Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 23 Approach 2 4 2 2 Catenary Joint 2 4 2 1 Catenary Section To define the properties of a catenary section right click on the Catenary Data item in the tree and select Insert Catenary Data gt Catenary Section Click on the Catenary Section object that you added and enter the following information in the Details panel The mass per unit length Mass Unit Length of the section of the composite mooring line The Equivalent Cross Sectional Area of the mooring line It is often more convenient especially with wire lines to specify this parameter so the buoyanc
162. ustnincdyiesa canieau ed Sannutaveimeultncaweanevenl 3 2 22 Attachi GOOmetry ata sa E EEEE EEE E aa San Ee eaS S E Ara EEE tee ca tes 4 2 2 1 General Modeling Requirements sssseesssssesssssesssssressssseesssrressserersssstessssstesssereesssreessssreessseess 5 2 2 2 Configuring the Geometry ssessesssssessssseessssressssseessssressssreessseressssseesssstessssstessseteesseseessssreesso 6 2 23 Add Fixed ROINtS aies arane a a E E a A a n eek 7 23 Define Parts B haviot c ape a E a e a a e a a aa a E a aAa 7 2 3 ls SUITACE Body aeir ao E EE E T EO AEE ET AE AE EEA E 10 2 3 2 Lie BOY sinense a a E a a a aaiae 11 23 3 POME MASS sce iduucecvertetacsa T o Ere EE EE EEE KEETE ENEEK A OEE OEVER EEE 12 RIA POINGBUOVANC YE Sy nas eraras ie Nei araa eA SE ES ie N E AA EA A A EA AAT tess 12 PAo PETA DI EENEN E A I AOE EAEE 12 2 3 6 Additional Hydrodynamic Stiffness isccsvsssasceaes toes vuevaseacavensceventavehtogs boerdudvaseabavesseesmetandnsays lobeds 13 2 3 7 Additional Damping Frequency Independent ccccccccsssssssseccceecceeseessnseeeeeeessseesnnneseeeees 14 2 3 8 Additional Added Mass Frequency Independent cccccccccssssesssstecceceeeeeessnneeeeeeeeeeseeensnaees 14 2 3 9 Current Force Coefficients enren eriein ie a i a a A E a i 14 2 3 10 Wind Force Coefficients socere ennen aE EEEa EEE EE EEEE ES 17 23 11 Str ct re CONNECTION POINKS w isressirrriasesiiesi ioris rrini o aT etero k T E AOE NEEE EEE 19 24 Def
163. v t y ll w a DA JL Fluid Dynamics Structural Mechanics Electromagnetics Systems and Multiphysics a Aqwa User s Manual ANSYS Inc Release 15 0 Southpointe November 2013 275 Technology Drive Canonsburg PA 15317 ANSYS Inc is ansysinfo ansys com certified to ISO http www ansys com 9001 2008 T 724 746 3304 F 724 514 9494 Copyright and Trademark Information 2013 SAS IP Inc All rights reserved Unauthorized use distribution or duplication is prohibited ANSYS ANSYS Workbench Ansoft AUTODYN EKM Engineering Knowledge Manager CFX FLUENT HFSS 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 in the United States or other countries ICEM CFD is a trademark used by ANSYS Inc under license CFX is a trademark of Sony Corporation in Japan All other brand product service and feature names or trademarks are the property of their respective owners Disclaimer Notice THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS INC ITS SUBSIDIARIES OR LICENSORS The software products and documentation are furnished by ANSYS Inc its subsidiaries or affiliates under a software license agreement that contains provisions concerning non disclosure copying length and nature of use compliance with exporting law
164. v Only excludes those calculated on diffracting panels instead these are included under the Diffraction Forces These values are calculated at the center of gravity and are available in all translational and rotational component directions Plot availability e Line graph presentation Force Moment plotted against Time Line Graph Input Use the Component input to select which Structure Force Moment component to plot either X Y or Z for force components or RX RY or RZ for rotational components Line Graph Output Maximum Value and Minimum Value of the Structure Force and the Time at which they occur Position of Min in X Position of Max in X These values can be parameterized by selecting the adjacent check box Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 84 of ANSYS Inc and its subsidiaries and affiliates Solution 2 8 2 2 5 Fender Forces Result Description 2D graphs to illustrate the fender forces during the analysis You must select the Structure and Con nection to that structure connected Fender for which you want to display the results Plot availability e Line graph presentation Force plotted against Time Line Graph Input Use the Component input to select which Fender Force component to plot either X Y or Z force components or one of the following Total Force Compression Force Elastic Force Damping Force Friction Force Horizont
165. ve has been performed Detailed hydrostatic results are available by selecting the Properties tab at the bottom of the graphical view In the Details panel select the Structure whose results you want to display You can add as many Hy drostatic results objects as you like to display the results of different structures For each result object you can suppress or enable the display of the Center of Gravity Center of Buoyancy and Center of Flotation information from the Details panel Any number of Hydrostatic results objects can be added to the Solution Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information 70 of ANSYS Inc and its subsidiaries and affiliates Solution toes Nyp redynarne Dih tao ANSTS AQWA HYDRO OUTRACT Vie Cit Yew is te id 9 EJ DEG Momoa E StQQahQaeex S Ge retisk T I 3 Propect AQWA Hydrostatic Revelts Seri Strecture FSRu Hy drostane Stiffeess Ceatre of Grawty Poston X 149 MAE re 9 993965 m z Sn RX R Heave Z 19311208 Nim 412 7475 4176376 5 N RRX 2643 669 N mim 87 17900 Nm j PacthRZ 2 2828306 N mim Eses lt e 7 Hydrostate Displacement Properties poe Actual Vobametice Duplacement no Std ah Equevalert Vobsmmetric Displacement 7 Pont Pend A nen Centre of Buoyancy Postion X 149 MAB 9 999966 m 2 1201 m Ou of Bance Forces Weaglt FX 0400309 FY 3455507 FZ 18916 A7 Ware enone Ort of Balance Moments Weight MX 1 0640
166. y e Line graph presentation static Force Moment plotted against X position either for All Components or Z Components Only Line graph presentation RAO Force Moment plotted against either Position Direction or Frequency Line graph presentation RAO Phase Angle plotted against either Position Direction or Frequency Surface graph presentation RAO Force Moment plotted against Direction Frequency Direction Pos ition or Frequency Position Surface graph presentation RAO Phase Angle plotted against Direction Frequency Direction Position or Frequency Position The Frequency Scale can be modified to be Period Scale if required Line Graph Input e Use the Component input to select which force component to plot either X Y or Z for forces or RX RY or RZ for moments When the plot is performed against Direction RAO then the required frequency can be chosen using the Frequency input and the Position can be entered When the plot is performed against Frequency RAO then the required direction can be chosen using the Direction input and the Position can be entered e When the plot is performed against Position RAO then the required direction can be chosen using the Direction input and the required frequency can be chosen using the Frequency input Line Graph Output Maximum Value and Minimum Value of Angle or Force Moment and the first Frequency Direction or Position at which they occu
167. y of the line may be calculated and subtracted from the structural weight to give the weight in water This parameter may also be specified as zero if the mass per unit length is input as the mass of the line LESS the mass of the displaced water per unit length this does not apply to the cases when cable dynamic analysis is required for which a non zero equivalent cross section area must be defined The stiffness of the line Stiffness EA specified in terms of EA where E is Youngs modulus and A is the cross sectional area of the line The default value is chosen to give a typical value based on the mass unit length Clearly this may be in error if the mass per unit length specified includes buoyancy effects The Maximum Tension which is the highest value of tension that should be used in the database created for this composite mooring line It is important that this is a realistic value If a very high value is input the database will cover a very large range of tensions and the accuracy in the actual working range may be reduced If a very small value is input the database will only cover a small range of tensions and constant tension may occur for larger strain values i e no extrapolation is carried out If cable dynamics is utilized this limiting value is not applied The Axial Stiffness Coefficients k1 k2 k3 A cable may have nonlinear axial stiffness The stiffness is calculated using the formula EA c EA const k1 e
168. ynamic Analysis System Each analysis type is represented by an analysis system that includes the individual components of the analysis such as the associated geometry and model properties Most analyses are represented by one independent analysis system However an analysis with data transfer can exist where results of one analysis are used as the basis for another analysis In this case an analysis system is defined for each analysis type where components of each system can share data To create an analysis system expand the Analysis Systems section in the Toolbox and drag an analysis object template onto the Project Schematic The analysis system is displayed as a vertical array of cells schematic where each cell represents a component of the analysis system Address each cell by right clicking on the cell and choosing an editing option Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 3 Approach e To create an analysis system with data transfer to be added to an existing system drag the object template representing the upstream analysis directly onto the existing system such that red boxes enclose cells that will share data between the systems After you release the mouse button the two systems are dis played including an interconnecting link and a numerical designation as to which cells share data See Working through a
169. zing 4 1 3 COORDINATE Card with Rotation Node Generation Not Supported 4 1 4 COORDINATE STRUCTURE Card Parts Structures 4 1 5 COORDINATE OFFSET card Not Supported 4 1 6 COORDINATE card with TRANSLATION Not Supported 4 1 7 COORDINATE Card with Mirror Node Gen 4 1 8 NOD5 card 5 digit node numbers Not Supported Always enabled 4 2 Deck 2 ELM Element Topology 4 2 0 General Description 4 2 1 Deck Header 4 2 2 ELEMENT TOPOLOGY Card Mesh Mesh Sizing Line Bodies Point Mass Point Buoyancy Disc 4 2 3 SYMX and SYMY X and Y Symmetry Cards Not Supported 4 2 4 HYDI card Hydrodynamic Interaction Structure Selection 4 2 5 RMXS RMYS cards Remove Symmetry Not Supported 4 2 6 MSTR Card Move Structure Not Supported 4 2 7 FIXD Card Fix Structure Parts Structures 4 2 9 VLID Card Suppression of Standing Waves Parts Structures Surface Bodies 4 2 10 ASYM Axi Symmetric Structure Generation Not Supported Release 15 0 SAS IP Inc All rights reserved Contains proprietary and confidential information of ANSYS Inc and its subsidiaries and affiliates 103 Appendix Aqwa Manual Reference Aqwa Editor Tree Object 4 2 11 ILID Card Suppression of Irregular Frequencies 4 2 12 ZLWL Card Waterline Height Surface Bodies Geometry 4 3 Deck 3 MATE Material Properties 4 3 0 General

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