# Extremely slow simulation with interDyMFoam

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 April 18, 2013, 05:16 Extremely slow simulation with interDyMFoam #1 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 5 Hi, I am running a simulation with interDyMFoam (Air/Water, AMI with rotating and stationary mesh) which runs extremely slow, and I am looking for some ways to improve the performance. The main reason seems to be low time steps (e-8) to keep the Courant number < 1, but it should be possible to speed up the calculation of every time step I think. I am looking for some comments on the residual targets/tolerances set in fvSolution, and maybe on my fvSchemes file also? I recently increased the toleranse of the pressure terms to 1e-6 instead of 1e-8 too increase the speed of the simulations, could this be further increased? I am running decomposed on 128 cores by the way. Any tips on how to improve the performance will be greatly appreciated. Regards, Jone Some output: Code: ```Interface Courant Number mean: 6.455324963e-06 max: 0.5005681575 Courant Number mean: 0.0002116964997 max: 0.5882487797 deltaT = 5.569042488e-08 Time = 0.006919137503 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.006919137503 transformation: ((0 0 0) (0.9738608726 (0 0.2271453297 0))) AMI: Creating addressing and weights between 4453 source faces and 4453 target faces AMI: Patch source weights min/max/average = 0.9985002144, 1.001921397, 1.000047858 AMI: Patch target weights min/max/average = 0.9990857617, 1.001532226, 1.000018088 Execution time for mesh.update() = 0.07 s MULES: Solving for alpha1 Phase-1 volume fraction = 0.00295762538 Min(alpha1) = -1.735479458e-18 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.002957636622 Min(alpha1) = -1.731270876e-18 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.002957647861 Min(alpha1) = -1.732182027e-18 Max(alpha1) = 1 GAMG: Solving for p_rgh, Initial residual = 0.02411778836, Final residual = 8.942364364e-07, No Iterations 40 time step continuity errors : sum local = 2.893569178e-13, global = 4.456094558e-14, cumulative = 9.7491866e-11 GAMG: Solving for p_rgh, Initial residual = 0.01070900624, Final residual = 8.263136668e-07, No Iterations 17 time step continuity errors : sum local = 2.632099118e-13, global = -7.978696644e-15, cumulative = 9.74838873e-11 ExecutionTime = 61236.58 s ClockTime = 61388 s Interface Courant Number mean: 6.448986145e-06 max: 0.5055292675 Courant Number mean: 0.0002114044481 max: 0.5878898938 deltaT = 5.504594754e-08 Time = 0.006919192549 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.006919192549 transformation: ((0 0 0) (0.9738604585 (0 0.2271471051 0))) AMI: Creating addressing and weights between 4453 source faces and 4453 target faces AMI: Patch source weights min/max/average = 0.9985011005, 1.001921476, 1.00004786 AMI: Patch target weights min/max/average = 0.9990854226, 1.001532248, 1.000018089 Execution time for mesh.update() = 0.07 s MULES: Solving for alpha1 Phase-1 volume fraction = 0.002957658974 Min(alpha1) = -1.733118704e-18 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.002957670084 Min(alpha1) = -1.733538446e-18 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.002957681198 Min(alpha1) = -1.734437289e-18 Max(alpha1) = 1 GAMG: Solving for p_rgh, Initial residual = 0.02904518995, Final residual = 8.139273874e-07, No Iterations 38 time step continuity errors : sum local = 2.577957076e-13, global = -5.558341087e-14, cumulative = 9.742830389e-11 GAMG: Solving for p_rgh, Initial residual = 0.01185015756, Final residual = 8.340824853e-07, No Iterations 24 time step continuity errors : sum local = 2.717511422e-13, global = 4.323848088e-14, cumulative = 9.747154237e-11 ExecutionTime = 61237.22 s ClockTime = 61389 s``` My fvSolution: Code: ```FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { pcorr { solver GAMG; tolerance 1e-06; //1e-08 relTol 0; smoother DIC; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } p_rgh { solver GAMG; tolerance 1e-06; //1e-08 relTol 0; smoother DIC; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } p_rghFinal { solver GAMG; tolerance 1e-06; //1e-08 relTol 0; smoother DIC; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-06; relTol 0; nSweeps 1; } UFinal { solver smoothSolver; smoother GaussSeidel; tolerance 1e-06; relTol 0; nSweeps 1; } } PIMPLE { momentumPredictor no; //yes nCorrectors 2; nNonOrthogonalCorrectors 0; nAlphaCorr 1; nAlphaSubCycles 3; cAlpha 1.5; correctPhi no; /* pRefPoint (0.0013 0.0017 0.0017); pRefValue 1e5; */ } relaxationFactors { fields { } equations { "U.*" 1; } } // ************************************************************************* //``` fvSchemes: Code: ```FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { div(rho*phi,U) Gauss limitedLinearV 1; div(phi,alpha) Gauss vanLeer01; div(phirb,alpha) Gauss interfaceCompression; //Following added because of crash on Vilje div((muEff*dev(T(grad(U))))) Gauss linear; div((nuEff*dev(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear limited 1.0; } interpolationSchemes { default linear; } snGradSchemes { default limited 1.0; } fluxRequired { default no; p_rgh; pcorr; alpha; } // ************************************************************************* //```

 April 22, 2013, 11:56 #2 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 9 increasing the tolerance is definitely not what i would raccomand. you are trading a small speedup for accuracy. definitely a no-no. any chanches you can use a coarser mesh? the courant number is set by the cell size and the flow velocity so increasing the cell size lowers the Courant number, thus allowing a higher timestep. also, check your maeh, maybe it is just a cell or two that are small and are slowing down all the simulation. I don't know if this strategy is doable for your case though. another thing you might want to try is to initialize the case with the mesh steady, maybe even using LTSInterFoam, even without turbulent quantities, just to do not start you simulation with big local velocities given by the mesh movement (I'm just guessing, something like a propeller rotating at 300 rpm, inflow velocity 10 ms, and there you go, big relative speed between flow and mesh motion, because the flow haven't picked it up yet...) __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

 April 22, 2013, 12:45 #3 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,698 Rep Power: 27 Hi Jone, From my experience with moving meshes and VOF methods, then you really have to consider the following: Code: ```momentumPrediction on; nCorrectors 3; // At least. I sometimes use as many as 5 nNonOrthogonalCorrectors ?;``` With respect to the non-orthogonal correctors, then you are using a method with rotating meshes, which must give rise to at least occasional high non-orthogonalities. In addition, I have read some threads about poor performance of the AMI on a large number of processors. You might consider the need of 128 processors, now that one iteration only takes 0.64 s. Kind regards Niels

April 22, 2013, 14:21
#4
Senior Member

Vieri Abolaffio
Join Date: Jul 2010
Location: Always on the move.
Posts: 308
Rep Power: 9
Quote:
 Originally Posted by ngj Hi Jone, From my experience with moving meshes and VOF methods, then you really have to consider the following: Code: ```momentumPrediction on; nCorrectors 3; // At least. I sometimes use as many as 5 nNonOrthogonalCorrectors ?;``` With respect to the non-orthogonal correctors, then you are using a method with rotating meshes, which must give rise to at least occasional high non-orthogonalities. In addition, I have read some threads about poor performance of the AMI on a large number of processors. You might consider the need of 128 processors, now that one iteration only takes 0.64 s. Kind regards Niels
silly me, I haven't noticed that. how big is your mesh?
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Naval architecture and CFD consultancy

 April 22, 2013, 16:55 #5 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 5 Vieri and Nils, thank you very much for your answers! I will look into them tomorrow morning. My mesh is around 1 million cells, so not that big. In CFX it takes less than 1/10 of the time with 4 millions, so I really donīt get it. I agree that the mesh might be the reason, I actually think that there are a couple of very small cells limiting the simulation time. Maybe I can find a way to limit the min cell size in Ansys Meshing to compare the speed. Initialization is a very good idea that I will look into. Have a good evening! Regards, Jone

 April 22, 2013, 17:02 #6 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 9 128 cores for a 1 million mesh it is really too much. I do think that you are getting too much mpi communication overhead. try with a more reasonable number, like 20-40 cores top. __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

 April 23, 2013, 04:50 #7 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 5 First of all, I also tried with a coarser mesh. It was ok in checkMesh, but it stilled crashed with the following error: Code: ```#0 Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #2 in "/lib/x86_64-linux-gnu/libc.so.6" #3 void Foam::MULES::limiter(Foam::Field&, Foam::geometricOneField const&, Foam::GeometricField const&, Foam::GeometricField const&, Foam::GeometricField const&, Foam::zeroField const&, Foam::zeroField const&, double, double, int) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" #4 void Foam::MULES::limit(Foam::geometricOneField const&, Foam::GeometricField const&, Foam::GeometricField const&, Foam::GeometricField&, Foam::zeroField const&, Foam::zeroField const&, double, double, int, bool) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" #5 Foam::MULES::explicitSolve(Foam::GeometricField&, Foam::GeometricField const&, Foam::GeometricField&, double, double) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" #6 in "/opt/openfoam211/platforms/linux64GccDPOpt/bin/interDyMFoam" #7 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #8 in "/opt/openfoam211/platforms/linux64GccDPOpt/bin/interDyMFoam"``` Last timesteps: Code: ```Interface Courant Number mean: 1.597370001e-13 max: 3.367889415e-08 Courant Number mean: 8.492343262e-05 max: 47.93150517 deltaT = 1.542054914e-14 Time = 5.124667456e-05 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 5.124667456e-05 transformation: ((0 0 0) (0.9999985598 (0 0.001697167211 0))) AMI: Creating addressing and weights between 1860 source faces and 1860 target faces AMI: Patch source weights min/max/average = 0.9999999855, 1.000273407, 1.00002072 AMI: Patch target weights min/max/average = 0.9999986967, 1.000284245, 1.000020412 Execution time for mesh.update() = 0.25 s --> FOAM Warning : From function Time::operator++() in file db/Time/Time.C at line 1010 Increased the timePrecision from 10 to 11 to distinguish between timeNames at time 5.124667455e-05 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101492e-05 Min(alpha1) = -2.94026316e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101492e-05 Min(alpha1) = -2.940263151e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101493e-05 Min(alpha1) = -2.940263144e-21 Max(alpha1) = 1 smoothSolver: Solving for Ux, Initial residual = 0.03289536739, Final residual = 5.931840904e-09, No Iterations 22 smoothSolver: Solving for Uy, Initial residual = 0.02652586093, Final residual = 6.490399401e-09, No Iterations 21 smoothSolver: Solving for Uz, Initial residual = 0.06385161287, Final residual = 9.329710362e-09, No Iterations 22 GAMG: Solving for p_rgh, Initial residual = 0.8168173646, Final residual = 5.329552555e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5691559964, Final residual = 4.333370438e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6077577617, Final residual = 5.096296929e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5588035124, Final residual = 4.970930311e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6553288826, Final residual = 6.082410996e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6012161847, Final residual = 5.743818456e-09, No Iterations 20 time step continuity errors : sum local = 2.767907786e-13, global = 6.720125451e-14, cumulative = -4.563931424e-06 GAMG: Solving for p_rgh, Initial residual = 0.7547558975, Final residual = 8.26595506e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4767521403, Final residual = 4.33189641e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.500681991, Final residual = 5.307664532e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4631253002, Final residual = 4.796368045e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5959068421, Final residual = 6.221265876e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5300655458, Final residual = 5.512629022e-09, No Iterations 20 time step continuity errors : sum local = 6.317765168e-13, global = 1.567796998e-13, cumulative = -4.563931267e-06 GAMG: Solving for p_rgh, Initial residual = 0.6942039022, Final residual = 7.554443004e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5165126574, Final residual = 5.254193207e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6475607497, Final residual = 6.787541225e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5574720976, Final residual = 5.810655172e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.7423454876, Final residual = 7.734423209e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6165483516, Final residual = 6.41331222e-09, No Iterations 20 time step continuity errors : sum local = 1.508767972e-12, global = 3.749318923e-13, cumulative = -4.563930892e-06 GAMG: Solving for p_rgh, Initial residual = 0.8276795512, Final residual = 8.954560476e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.558609031, Final residual = 5.530478839e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6826850609, Final residual = 7.158367366e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5769959496, Final residual = 5.989697425e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.7749635251, Final residual = 8.06470252e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6336308451, Final residual = 6.581617802e-09, No Iterations 20 time step continuity errors : sum local = 3.559817726e-12, global = 8.850757951e-13, cumulative = -4.563930007e-06 GAMG: Solving for p_rgh, Initial residual = 0.8547424795, Final residual = 9.199343842e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5841017513, Final residual = 5.844350229e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.7306124828, Final residual = 7.63158262e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6069032171, Final residual = 6.294821239e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.8194731067, Final residual = 8.514487236e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6594746017, Final residual = 6.843822577e-09, No Iterations 20 time step continuity errors : sum local = 8.411599725e-12, global = 2.092559032e-12, cumulative = -4.563927914e-06 ExecutionTime = 501.96 s ClockTime = 502 s Interface Courant Number mean: 1.770494893e-13 max: 4.980492024e-08 Courant Number mean: 0.0002330663221 max: 139.7058538 deltaT = 1.103786901e-15 Time = 5.1246674565e-05 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 5.124667456e-05 transformation: ((0 0 0) (0.9999985598 (0 0.001697167211 0))) AMI: Creating addressing and weights between 1860 source faces and 1860 target faces AMI: Patch source weights min/max/average = 0.9999999855, 1.000273407, 1.00002072 AMI: Patch target weights min/max/average = 0.9999986967, 1.000284245, 1.000020412 Execution time for mesh.update() = 0.23 s --> FOAM Warning : From function Time::operator++() in file db/Time/Time.C at line 1010 Increased the timePrecision from 11 to 12 to distinguish between timeNames at time 5.124667456e-05 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101493e-05 Min(alpha1) = -2.940263142e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101493e-05 Min(alpha1) = -2.94026314e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 2.340101493e-05 Min(alpha1) = -2.940263136e-21 Max(alpha1) = 1 smoothSolver: Solving for Ux, Initial residual = 0.06477118372, Final residual = 8.642332518e-09, No Iterations 26 smoothSolver: Solving for Uy, Initial residual = 0.02933841898, Final residual = 6.713449257e-09, No Iterations 25 smoothSolver: Solving for Uz, Initial residual = 0.1070822693, Final residual = 8.780816192e-09, No Iterations 27 GAMG: Solving for p_rgh, Initial residual = 0.8893907442, Final residual = 6.03093516e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.2999964081, Final residual = 4.400563944e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2001912473, Final residual = 4.323988997e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.1991798232, Final residual = 4.856585103e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2166203943, Final residual = 5.449721145e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2325097647, Final residual = 5.987364552e-09, No Iterations 19 time step continuity errors : sum local = 2.31991253e-13, global = 4.653817902e-14, cumulative = -4.563927868e-06 GAMG: Solving for p_rgh, Initial residual = 0.2530189377, Final residual = 6.73790163e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2376544809, Final residual = 6.337231792e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2508918284, Final residual = 7.096666627e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.2671706917, Final residual = 7.384764598e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.3142132031, Final residual = 8.694850032e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.3269917566, Final residual = 8.999909757e-09, No Iterations 19 time step continuity errors : sum local = 4.947432806e-13, global = 1.061610488e-13, cumulative = -4.563927762e-06 GAMG: Solving for p_rgh, Initial residual = 0.3896779346, Final residual = 4.01177967e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.3602979394, Final residual = 9.679480202e-09, No Iterations 19 GAMG: Solving for p_rgh, Initial residual = 0.4086001377, Final residual = 4.23695469e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4096242098, Final residual = 4.220163954e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4891555194, Final residual = 5.018675493e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4798885981, Final residual = 4.903916905e-09, No Iterations 20 time step continuity errors : sum local = 4.304573434e-13, global = 9.361216275e-14, cumulative = -4.563927668e-06 GAMG: Solving for p_rgh, Initial residual = 0.5731626992, Final residual = 5.785088066e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.4692696901, Final residual = 4.65822784e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5222446816, Final residual = 5.323751511e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5051875075, Final residual = 5.107623445e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6048712058, Final residual = 6.10837163e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5734690483, Final residual = 5.770318327e-09, No Iterations 20 time step continuity errors : sum local = 9.866099684e-13, global = 2.125564627e-13, cumulative = -4.563927455e-06 GAMG: Solving for p_rgh, Initial residual = 0.6854054465, Final residual = 6.829505031e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.537832268, Final residual = 5.286631514e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5994082542, Final residual = 6.028535219e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5680692402, Final residual = 5.673560985e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6801833379, Final residual = 6.789791194e-09, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.6322346784, Final residual = 6.292624607e-09, No Iterations 20 time step continuity errors : sum local = 2.267217457e-12, global = 4.844195478e-13, cumulative = -4.563926971e-06 ExecutionTime = 540.1 s ClockTime = 540 s Interface Courant Number mean: 1.178773889e-13 max: 3.493308291e-08 Courant Number mean: 8.800536524e-05 max: 51.12002034 deltaT = 2.159206695e-16 Time = 5.12466745648e-05 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 5.124667456e-05 transformation: ((0 0 0) (0.9999985598 (0 0.001697167211 0))) AMI: Creating addressing and weights between 1860 source faces and 1860 target faces AMI: Patch source weights min/max/average = 0.9999999855, 1.000273407, 1.00002072 AMI: Patch target weights min/max/average = 0.9999986967, 1.000284245, 1.000020412 Execution time for mesh.update() = 0.25 s``` I played around with the parameters in fvSolution for this one with no success. About the number of cores you are right, it is too many. But anyway it has been running way faster with 128 than with 8 cores. I heard before that there should be around 50k cells for each core, so 20 could be a good number of cores. I am trying to initialize with potentialFoam by adding these lines to fvSolutions: Code: ```potentialFlow { nNonOrthogonalCorrectors 10; }``` How can I use LTSInterFoam to initialize? The quantities are quite large as you say, inlet speed of almost 40 ms-1 and quick rotation.

 April 23, 2013, 07:55 #8 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 9 your simulation is beyond recovery earlier than that. with the auto time stepping you are already at a DeltaT =1e-14 s, average courant number of 8 and max Co 45. i dont' know what you changed or if it is the mesh but something went horribly wrong earlier. I'd suggest to disable the autotimestep, at least for the tests. in this way if there is an issue the sim crashes instantly instead of dragging up wasting time. consider it as euthanasia. to initialize the solution, change the time scheme in your control dict and just run LTSInterFoam instead of interDyMFoam. it will tell you if something is amiss. if you want to be really cool, add a MRF zone at your rotating region. than you can bring the developed field into your simulation. __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

April 23, 2013, 08:01
#9
Member

Anon
Join Date: Oct 2012
Posts: 33
Rep Power: 5
Quote:
 Originally Posted by sail your simulation is beyond recovery earlier than that. with the auto time stepping you are already at a DeltaT =1e-14 s, average courant number of 8 and max Co 45. i dont' know what you changed or if it is the mesh but something went horribly wrong earlier. I'd suggest to disable the autotimestep, at least for the tests. in this way if there is an issue the sim crashes instantly instead of dragging up wasting time. consider it as euthanasia. to initialize the solution, change the time scheme in your control dict and just run LTSInterFoam instead of interDyMFoam. it will tell you if something is amiss. if you want to be really cool, add a MRF zone at your rotating region.
Thank you Vieri!

So should I run the full simulation with LTSInterFoam, or just the first timestep(s)? How do I apply the result so that it initializes interDyMFoam?

About this particular simulation that crashed it must be something wrong with the mesh. I tried to make a coarser mesh just for testing, but I guess it resolves the flow very poorly.

 April 23, 2013, 10:14 #10 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 9 it is very problem dependent, but i'd say run not necessarly until convergence, but not far from it either. 1000-3000 iterations, maybe? use mapFields to move the data or just edit manually the BCs if needed. __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

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