How to get steady result in pitzDaily using LES model
Hi Foamers,
I am trying to use simpleFoam to solve pitzDaily with LES model and compare the results between LES model and RAS model (k-epsilon model). And I change part codes in tutorials(incompressibel/pisoFoam/les/pitzDaily), but the caculation is not convergent no matter how long the running time I set. Here is my changes: 1.fvsolution solvers { p { solver GAMG; tolerance 1e-06; relTol 0.1; smoother GaussSeidel; } pFinal { $p; smoother DICGaussSeidel; tolerance 1e-06; relTol 0; } "(U|k|B|nuTilda|s)" { solver smoothSolver; smoother GaussSeidel; tolerance 1e-05; relTol 0; } } SIMPLE { nNonOrthogonalCorrectors 0; consistent yes; residualControl { p 1e-2; "(pFinal|U|B|nuTilda|s)" 1e-3; } } relaxationFactors { equations { U 0.9; // 0.9 is more stable but 0.95 more convergent ".*" 0.9; // 0.9 is more stable but 0.95 more convergent } } 2.conrtolDict application simpleFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 2000; deltaT 1; writeControl timeStep; writeInterval 100; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression off; timeFormat general; timePrecision 6; runTimeModifiable true; Please tell why I can not get steady result in LES model Best regards, yuanjiahui |
Do your calculations with a transient solver like pisoFoam or pimpleFoam. Then compare similar time steps.
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You have to use a transient solver for LES but for comparison with RAS results, you can add "fieldAverage" function within controlDict for getting the mean values of U and p.
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Hi mzzmrt.Can I get a steady result with a transient solver like pisoFoam in LES model?
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In short, no. pisoFoam calculates a transient, time dependant solution. And you use LES to resolve the transient flow without averaging like RAS does.
If you want a steady, time independant, solution use simpleFoam and a RAS model. If you want to compare LES and RAS, you can do so by comparing the steady RAS and the transient RAS and LES results. |
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regards |
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Conduct both for the same runtime. |
Add this to your controlDict, solve LES with pisoFoam and check the results in paraview:
functions { fieldAverage1 { type fieldAverage; functionObjectLibs ("libfieldFunctionObjects.so"); enabled true; outputControl outputTime; fields ( U { mean on; prime2Mean off; base time; } p { mean on; prime2Mean off; base time; } ); } } |
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