# [snappyHexMesh] Problem in results with snappyHexMesh between refinement levels

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 November 8, 2018, 04:46 Problem in results with snappyHexMesh between refinement levels #1 New Member   Phil Join Date: Sep 2018 Posts: 3 Rep Power: 5 Hi, i ran into a problem when solving a case for external flows around a car with pisoFoam and snappyHexMesh. You can clearly see a big influence from the mesh between different refinement levels (see attached pictures) Above the Car one can clearly see the edges of the different refinement levels in the velocity profile. I have the same problem in the transition between the layers and the surrounding mesh at the front of the car (see attached picture). Has anyone an idea what seems to be the problem? I also did the motorbike tutorial to see if this problem happens there too. And in some Areas you can clearly see those boundary lines in the velocity profile. I dont think that this is a Problem with snappyHexMesh itself, because it is commonly used. But what am I doing wrong? I write the content from fvSchemes fvSolution and SnappyHexMesh in the next post. Hope one of you can help me U_profile_above_car.jpg U_profile_above_car_with_mesh.jpg car_front_U_profile.png

 November 8, 2018, 04:49 fvSolution #3 New Member   Phil Join Date: Sep 2018 Posts: 3 Rep Power: 5 solvers { p { solver GAMG; tolerance 1e-6; //relTol 0.01; smoother GaussSeidel; nPreSweeps 0; nPostSweeps 1; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 20; agglomerator faceAreaPair; mergeLevels 1; } pFinal { \$p; tolerance 1e-06; relTol 0; } "(U|k|kl|kt|omega)" { solver GAMG; smoother GaussSeidel; tolerance 1e-06; //relTol 0.01 nPreSweeps 0; nPostSweeps 1; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 20; agglomerator faceAreaPair; mergeLevels 1; } "(U|k|kl|kt|omega)Final" { \$U; tolerance 1e-06; relTol 0; } } PISO { nOuterCorrectors 1; nCorrectors 2; nNonOrthogonalCorrectors 1; pRefCell 0; pRefValue 0; } relaxationFactors { equations { p 0.3; // 0.9 is more stable but 0.95 more convergent "(U|k|kl|kt|omega)" 0.7; // 0.9 is more stable but 0.95 more convergent } }