2way FSI of a wing
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Hi everyone! I got stuck in solving a 2way FSI problem for my Final Year Project. Hope someone could please help me with it...
The project is to simulate the fluid flow around a 3D wing with a morphing wing structure installed. The final objective is to obtain the stress distribution in the mechanism. Before solving the real problem, I was planned to do a validation case to obtain a valid method. For the validation case, I chose a 3D straight wing with a NACA 0012 airfoil. In this case, CFX and Transient Structural are chosen as the CFD and structure solvers respectively. I've tested the problem settings on a simple cuboid in the case which the solver ran properly and was able to generate reasonable results. However, when I apply the same settings on my wing, the solver always terminated without any results generated. As shown in the CFX solver report, there are some problems with the mesh quality. However, I really cannot figure out the problem by myself... Could anyone please give me some suggestions that may help me to improve the mesh? Or are there any external meshers (like ICEM) that could be used for such a 2way FSI problem? (p.s. the attachment shows my previous mesh of the fluid field.) Thanks and Best Regards, 
hi,
i am currently working on a quiet similar problem. what error shows up if the solver is crashing ? i generally would suggest a hexmesh since very fine tet/prismelementation at the wing would cause very bad angles if the wing is moving. neewbie 
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++  Job Information  ++ Run mode: serial run Host computer: MENTW121 (PID:6456) Job started: Wed Jan 11 16:35:52 2012 ++  Memory Allocated for Run (Actual usage may be less)  ++ Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node Real 5405.0 61.07 14.44 21113.4 244.28 Integer 7194.3 81.29 19.22 28102.6 325.15 Character 200.0 2.26 0.53 195.3 2.26 Logical 10.0 0.11 0.03 39.1 0.45 Double 265.5 3.00 0.71 2074.3 24.00 ================================================== ==================== Interpolating Onto Domain "Default Domain" ================================================== ==================== Total Number of Nodes in the Target Domain = 88504 Bounding Box Volume of the Target Mesh = 3.57492E03 Checking all source domains from the source file: Target mesh is the same as domain "Default Domain". Start direct copying of variables from domain "Default Domain". ++  Variable Range Information  ++ ++  Variable Name  min  max  ++  Velocity u.Beta  1.97E06  1.00E+00   Velocity v.Beta  8.94E08  1.00E+00   Velocity w.Beta  1.04E07  1.00E+00   Courant Number  3.22E+01  4.50E+03   Mesh Coordinates  4.61E19  2.24E01   Effective Density at End of Timestep  1.18E+00  1.18E+00   Density  1.18E+00  1.18E+00   Mesh Diffusivity  1.00E+15  1.00E+15   Volume Porosity  1.00E+00  1.00E+00   Pressure.Gradient  4.42E01  9.28E+04   Velocity u.Gradient  1.77E03  1.12E+04   Velocity v.Gradient  2.32E02  9.47E+03   Velocity w.Gradient  3.61E03  2.73E+03   Mesh Displacement  0.00E+00  1.99E08   Total Mesh Displacement  0.00E+00  2.04E07   Absolute Pressure  1.01E+05  1.01E+05   Pressure  6.51E+01  6.91E+01   Total Pressure  2.04E+01  7.15E+01   Specific Volume  8.44E01  8.44E01   Shear Strain Rate  2.19E01  1.81E+04   Turbulence Eddy Dissipation  2.28E01  2.05E+05   Turbulence Eddy Frequency  3.83E+02  1.91E+05   Turbulence Kinetic Energy  1.38E03  1.34E+01   Velocity Correlation uu  9.96E03  1.56E+02   Velocity Correlation uv  2.43E+01  5.97E+01   Velocity Correlation uw  1.54E+01  3.63E+01   Velocity Correlation vv  2.72E11  4.90E+01   Velocity Correlation vw  1.08E+01  1.14E+01   Velocity Correlation ww  0.00E+00  2.26E+01   Velocity  2.66E01  1.30E+01   Dynamic Viscosity  1.83E05  1.83E05   Eddy Viscosity  4.52E08  1.82E04  ++ ++  CPU Requirements of Interpolation  ++ Interpolation Step Time Percentage (secs. %total)  Tree Setup 1.40E01 60.0 % Interpolation 1.56E02 6.7 % Miscellaneous 7.80E02 33.3 %  Total 2.34E01 ++  Job Information  ++ Host computer: MENTW121 (PID:6456) Job finished: Wed Jan 11 16:35:54 2012 Total CPU time: 2.340E01 seconds or: ( 0: 0: 0: 0.234 ) ( Days: Hours: Minutes: Seconds ) Total wall clock time: 2.000E+00 seconds or: ( 0: 0: 0: 2.000 ) ( Days: Hours: Minutes: Seconds ) ++    Solver    ++ ++    ANSYS CFX Solver 13.0     Version 2010.10.0123.02 Sat Oct 2 02:31:59 GMTDT 2010     Executable Attributes     singleint3264bitnovc8noifortnovc6optimisedsupfortnoprofnos    Copyright 2010 ANSYS Inc.  ++ ++  Job Information  ++ Run mode: serial run Host computer: MENTW121 (PID:6508) Job started: Wed Jan 11 16:35:57 2012 Connecting to the following master process: Host Name : MENTW121 Port Number : 56220 ++  Memory Allocated for Run (Actual usage may be less)  ++ Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node Real 38370.6 433.55 102.52 149885.1 1734.18 Integer 12594.9 142.31 33.65 49198.7 569.23 Character 3543.7 40.04 9.47 3460.7 40.04 Logical 80.0 0.90 0.21 312.5 3.62 Double 908.0 10.26 2.43 7093.8 82.08 ++  ****** Notice ******   The Total Centroid Displacement is being reinitialised using   the current mesh geometry.  ++ ++  Mesh Statistics  ++  Domain Name  Orthog. Angle  Exp. Factor  Aspect Ratio  +++++   Minimum [deg]  Maximum  Maximum  +++++  Default Domain  17.0 !  64 !  13 OK  +++++   %! %ok %OK  %! %ok %OK  %! %ok %OK  +++++  Default Domain  <1 2 98  <1 5 95  0 0 100  +++++ Domain Name : Default Domain Total Number of Nodes = 88504 Total Number of Elements = 374292 Total Number of Tetrahedrons = 311528 Total Number of Prisms = 62431 Total Number of Pyramids = 333 Total Number of Faces = 19838 ++  User Defined Monitor Information  ++ ++  ****** Notice ******     Monitor points have been defined in a moving mesh simulation.   Please note that the points are assigned to vertices located as   given below for the initial mesh. During the simulation, the   points may be reassigned to other vertices but the new   positions are not reported in the output file.  ++ Monitor Point: Monitor Point 1 Domain: Default Domain User specified location (x,y,z) : 9.945E01, 1.045E01, 0.000E+00 Assigned vertex location (x,y,z): 1.550E01, 4.650E02, 0.000E+00 Distance to specified location : 8.415E01 Valid variables from output variable list: Pressure ++  Initial Conditions Supplied by Fields in the Input Files  ++ Domain Name : Default Domain Absolute Pressure Courant Number Mesh Coordinates Mesh Diffusivity Mesh Displacement Pressure Pressure.Gradient Shear Strain Rate Specific Volume Total Mesh Displacement Total Pressure Velocity Velocity.Beta Velocity.Gradient Volume Porosity ++  Average Scale Information  ++ Domain Name : Default Domain Global Length = 1.5280E01 Minimum Extent = 9.3000E02 Maximum Extent = 2.4800E01 Density = 1.1850E+00 Dynamic Viscosity = 1.8310E05 Velocity = 9.2781E+00 Advection Time = 1.6469E02 RMS Courant Number = 1.1615E+03 Maximum Courant Number = 4.5011E+03 Reynolds Number = 9.1752E+04 ++  ERROR #002100004 has occurred in subroutine Out_Scales_Flu.   Message:   The Reynolds number is outside of the range expected based on the   Option selected for the TURBULENCE MODEL. Check this setting,   the values of the properties, mesh scale, consistency of units   and solution values in the input file. Execution will proceed.  ++ /* For this problem, I'm sure that I selected the LAMINAR MODEL and the Reynolds number is far less than the critical transition Reynolds number. I don't know why this error pumped up...*/ ++  Boundary Condition Data Supplied by External Solver Coupling  ++ ANSYS Multifield Solver : ANSYS CFX Boundary : Wing CFX Variable : Total Mesh Displacement ANSYS Interface : 1 ANSYS Variable : DISP ++  Checking for Isolated Fluid Regions  ++ No isolated fluid regions were found. ++  ****** Notice ******     The CFX results that are being used to initialise this   simulation were generated at a time value that is inconsistent   with the Coupling Initial Time value set in the CFX Input File.   Please review results carefully.   CFX results time : 1.0000E01   Coupling Initial Time : 0.0000E+00  ++ ++  The Equations Solved in This Calculation  ++ Subsystem : Mesh Displacement XDisp YDisp ZDisp Subsystem : Momentum and Mass UMom VMom WMom PMass CFD Solver started: Wed Jan 11 16:36:10 2012 ++  Convergence History  ++ ++  Writing transient file 0_CS.trn   Name : Transient Results 1   Type : Selected Variables   Option : Every Coupling Step  ++ ================================================== ====================  Timestepping Information    Timestep  RMS Courant Number  Max Courant Number  ++++  1.0000E01  999.99  999.99   ================================================== ==================== TIME STEP = 5 SIMULATION TIME = 1.0000E01 CPU SECONDS = 1.948E+02 (THIS RUN: 1 1.0000E01 4.368E+00)   COUPLING/STAGGER ITERATION = 1    SOLVING : Mesh Displacement    Equation  Rate  RMS Res  Max Res  Linear Solution  ++++++  XDisp  0.00  0.0E+00  0.0E+00  0.0E+00 OK  YDisp  0.00  0.0E+00  0.0E+00  0.0E+00 OK  ZDisp  0.00  0.0E+00  0.0E+00  6.9 0.0E+00 OK ++++++ ++  *** INSUFFICIENT MEMORY ALLOCATED ***     ACTION REQUIRED : Increase the real stack memory size.     Details :   Requested space : 324000 words   Current allocated space : 38370576 words   Current used space : 17850611 words   Current free space : 20519965 words   Number of free areas : 108  ++ /* It seems that the memory available is more than enough for what is required...*/ Fatal error generated in gCrdVxIp Message : FULL : Failed to make a data area for CrdVxIp gCrdVxIp called by : get_MVFLOW_ELIP ++  Writing crash recovery file  ++ ++  ERROR #001100279 has occurred in subroutine ErrAction.   Message:   Stopped in routine gCrdVxIp            ++ ++  An error has occurred in cfx5solve:     The ANSYS CFX solver exited with return code 1. No results file   has been created.  ++ End of solution stage. ++  The following transient and backup files written by the ANSYS CFX   solver have been saved in the directory   C:/Users/wang0537/AppData/Local/Temp/2Way   validation_6048_Working/dp0/CFX/CFX/Work1/Fluid Flow CFX_004:     0_CS.trn  ++ ++  An error has occurred in cfx5solve:     ANSYS Solver terminated with return code 3840  ++ ++  The results from this run of the ANSYS solver have been written to   C:\Users\wang0537\AppData\Local\Temp\2Way   validation_6048_Working\dp0\CFX\CFX\Work1\Fluid Flow CFX_004.ansys  ++ ++  Warning!     The ANSYS CFX Solver has written a crash recovery file. This file   has been saved as C:/Users/wang0537/AppData/Local/Temp/2Way   validation_6048_Working/dp0/CFX/CFX/Work1/Fluid Flow   CFX_004.res.err and may be an aid to diagnosing the problem or   restarting the run. More details should be available in the   solver output section of the output file.  ++ ++  The following user files have been saved in the directory   C:/Users/wang0537/AppData/Local/Temp/2Way   validation_6048_Working/dp0/CFX/CFX/Work1/Fluid Flow CFX_004:     mon  ++ This run of the ANSYS CFX Solver has finished. 
according to the numbers the memory should be sufficient.... did you try to change the stack size e.g. to 1.1?

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As newbie says, simply increase the memory allocation factors. You can do this on the solver manager under advanced.
Don't worry about the Re number warning. It is a warning, not an error and just a guide. If you are sure your flow is laminar then you have done the right thing. 
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The error message tells you which one is the problem  the real stack. But I would change them all provided you have enough memory to do so. Once you have it running you can reduce them to what is really needed.

I think he means the Solver, Partitioner and Interpolation tabs. It's the Solver tab you want in this case. Try increasing the Memory Allocation Factor to 1.2 or something similar.

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++  Mesh Statistics  ++  Domain Name  Orthog. Angle  Exp. Factor  Aspect Ratio  +++++   Minimum [deg]  Maximum  Maximum  +++++  Default Domain  23.4 ok  172 !  20 OK  +++++   %! %ok %OK  %! %ok %OK  %! %ok %OK  +++++  Default Domain  0 3 97  <1 5 95  0 0 100  +++++ And the Orthog. Angle also seems undesirable... How can I improve these two factors? 
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That is just a warning message, your simulation will still proceed. But pay attention to its advice  an expansion factor of 172 is pretty bad and you should try to do a better quality mesh.

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