# convergence problems

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July 13, 2012, 05:30
convergence problems
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Join Date: Jan 2012
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Hello,

I have some serious convergence problems (especially p) with a mesh for a flow simulation around a building. To simulate multiple angles, I merged two meshes and combined them with AMI. So my question, is this mesh too bad to run? Here are the checkMesh results:

Quote:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 1901408 faces: 12673529 internal faces: 12307391 cells: 5669490 boundary patches: 10 point zones: 0 face zones: 1 cell zones: 1 Overall number of cells of each type: hexahedra: 470000 prisms: 1352790 wedges: 0 pyramids: 10170 tet wedges: 0 tetrahedra: 3836530 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. *Number of regions: 2 The mesh has multiple regions which are not connected by any face. <
And here are my fvSchemes and fvSolution:
Quote:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; grad(k) cellLimited Gauss linear 1; grad(epsilon) cellLimited Gauss linear 1; } divSchemes { default none; div(phi,U) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(phi,nuTilda) Gauss upwind; div(R) Gauss linear; div((nuEff*dev(T(grad(U))))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p ; } // ************************************************** *********************** //
Quote:
 solvers { p { solver PCG; preconditioner DIC; tolerance 1e-06; relTol 0.01; } U { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } k { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } epsilon { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } R { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } nuTilda { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } } SIMPLE { nNonOrthogonalCorrectors 0; residualControl { p 1e-2; U 1e-3; "(k|epsilon|omega)" 1e-3; } } relaxationFactors { p 0.3; U 0.7; k 0.7; epsilon 0.7; R 0.7; nuTilda 0.7; } // ************************************************** *********************** //
I use simpleFoam and the k-e-realizable model for this simulation. I tried a simulation for zero angle of attack, everything works fine. But when I change the angle, I get problems with convergence.

I'll be really grateful for every advice.

Thanks,
slint

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