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Courant Number increasing too high PimpleFoam |
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Anon
Join Date: Dec 2020
Posts: 20
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Hi all,
This is a question which has been asked many times, unfortunately trying some of the suggestions applicable to my situation have not worked, so I hope someone can help now I have a simulation over open terrain. Over the weekend I simulated the flow using PimpleFoam over a coarse domain using a deltaT of 0.001 and a maxCo of 0.9. It ran for over 3 minutes, (the time I required it to run for), without the courant number increasing above 0.005. However, when I increase the blockMesh resolution even slightly to (15 10 4) from (10 5 2) shown in my blockMesh file below, with the same deltaT of 0.001, the courant number increases past 1 within 15 minutes and grows exponentially until it crashes. This is an issue, as it isn't close to how fine I need my resolution to be for the study My checkMesh produces no errors, with a max Non orthogonality of 56, average of 5. Finally, even with a maxCo of 0.9, using adjustTimeStep causes it to rise above 1 more quickly than without my case files are shown below blockMeshDict convertToMeters 1; vertices ( (-125 518150 0) (2180 518150 0) (2180 519320 0) (-125 519320 0) (-125 518150 450) (2180 518150 450) (2180 519320 450) (-125 519320 450) ); blocks ( hex (0 1 2 3 4 5 6 7) (10 5 2) simpleGrading (1 1 1) ); edges ( ); boundary ( outlet { type patch; faces ( (0 4 7 3) (1 5 4 0) ); } inlet { type patch; faces ( (2 6 5 1) ( 3 7 6 2 ) ); } DuneField { type wall; faces ( (0 3 2 1) ); } top { type patch; faces ( (4 5 6 7) ); } ); mergePatchPairs ( ); fvSchemes: ddtSchemes { default Euler; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; } divSchemes { default none; div(phi,U) bounded Gauss linearUpwind grad(U); div(phi,k) bounded Gauss upwind; div(phi,epsilon) bounded Gauss upwind; div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear orthogonal ; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p ; } wallDist { method meshWave; } fvSolution solvers { p { solver GAMG; tolerance 1e-5; relTol 0.01; smoother DICGaussSeidel; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } pFinal { $p; relTol 0; } "(U|k|epsilon)" { solver smoothSolver; smoother symGaussSeidel; tolerance 1e-05; relTol 0.1; } "(U|k|epsilon)Final" { $U; relTol 0; } } PIMPLE { nNonOrthogonalCorrectors 0; nCorrectors 2; } controlDict: application pimpleFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 10000000000; deltaT 0.002; writeControl adjustableRunTime; writeInterval 1; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression off; timeFormat general; timePrecision 6; runTimeModifiable yes; adjustTimeStep yes; libs ("libatmosphericModels.so"); maxCo 0.9; transportProperties transportModel Newtonian; nu nu [ 0 2 -1 0 0 0 0 ] 1e-05; CrossPowerLawCoeffs { nu0 nu0 [ 0 2 -1 0 0 0 0 ] 1e-06; nuInf nuInf [ 0 2 -1 0 0 0 0 ] 1e-06; m m [ 0 0 1 0 0 0 0 ] 1; n n [ 0 0 0 0 0 0 0 ] 1; } BirdCarreauCoeffs { nu0 nu0 [ 0 2 -1 0 0 0 0 ] 1e-06; nuInf nuInf [ 0 2 -1 0 0 0 0 ] 1e-06; k k [ 0 0 1 0 0 0 0 ] 0; n n [ 0 0 0 0 0 0 0 ] 1; } turbulenceProperties simulationType RAS; RAS { RASModel RNGkEpsilon; turbulence on; printCoeffs on; kEpsilonCoeffs { Cmu 0.09; C1 1.44; C2 1.92; sigmaEps 1.11; } } If any other files are needed, please let me know. Any advice would be greatly appreciated Last edited by CfdUser5855; January 11, 2021 at 07:16. Reason: Missing File |
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courant number, pimplefoam, turbuelence model |
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