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Question/Problem with Convergence - simpleFoam - Pipe-System |
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March 1, 2019, 03:19 |
Question/Problem with Convergence - simpleFoam - Pipe-System
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Hi there!
My Case I want to simulate a part of a Pipe-System (simpleFoam) filled with air. See the attached file for an overview, Diameters are from 250mm to 350mm at the tubes . The velocites are around ~ 24 m/s down to 2 m/s at the rectangular part. (Volumetric Flowrate up to 4200 m^3/h) https://www.cfd-online.com/Forums/me...-geometrie.jpg If needed i can post also some Pictures of my Mesh. Im generating the Mesh with SnappyHexMesh out of a Background-Mesh from gmsh. I tried several different mesh-types. First coarse / then fine /with Layers or without. CheckMesh always told me my mesh is ok. I specify the velocity at the inlet and the fluid can stream out free at the end of the rectangular part, where i set the pressure to 0. I'm using the kepsilon turbulence-model, but i also tried out the kOmegaSST. Before i start simpleFoam, im initializing the Domain with potentialFoam. My Problem I have the problem that the initial-residual of p is not dropping below the value 0,05 - 0,005. Also the other variables don't reach lower values. I'm struggling now if this is enough? I guess These values should fall much more for reaching convergence? The Results do look ok, Velocites are in the expected range. Also the pressure doesnt look false. So im uncertain right now, if the boundaries are ok for my case. I dont really trust my results.. I would be very grateful, if someone look over my case or can give me some advices what i can do better! Best regards! So here is a small part of my solution.output. Most times the values arent changing even after 1000+ iterations. Code:
Time = 150 smoothSolver: Solving for Ux, Initial residual = 0.00378163, Final residual = 3.17913e-005, No Iterations 19 smoothSolver: Solving for Uy, Initial residual = 0.00795081, Final residual = 6.85687e-005, No Iterations 23 smoothSolver: Solving for Uz, Initial residual = 0.00467368, Final residual = 4.40989e-005, No Iterations 18 GAMG: Solving for p, Initial residual = 0.0132319, Final residual = 8.3468e-009, No Iterations 23 GAMG: Solving for p, Initial residual = 0.00198833, Final residual = 8.91338e-009, No Iterations 14 GAMG: Solving for p, Initial residual = 0.000139475, Final residual = 5.24627e-009, No Iterations 10 GAMG: Solving for p, Initial residual = 1.69987e-005, Final residual = 5.30083e-009, No Iterations 7 time step continuity errors : sum local = 2.43281e-007, global = 6.73135e-009, cumulative = 1.22496e-008 smoothSolver: Solving for epsilon, Initial residual = 0.0105538, Final residual = 0.000100227, No Iterations 14 smoothSolver: Solving for k, Initial residual = 0.0144642, Final residual = 0.000144077, No Iterations 18 ExecutionTime = 2162.26 s ClockTime = 2162 s fvSchemes Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 5 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(U) cellLimited Gauss linear 1; } divSchemes { div(phi,U) Gauss linearUpwind grad(U); div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,omega) Gauss upwind; div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p ; } // ************************************************************************* // I already played with the Relaxation-values. The ones provided in Motorbike tutorials also didnt Change something Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 5 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p { solver GAMG; tolerance 1e-8; relTol 0; smoother GaussSeidel; nPreSweeps 0; nPostSweeps 2; cacheAgglomeration on; agglomerator faceAreaPair; nCellsInCoarsestLevel 120; mergeLevels 1; maxIter 500; } Phi { $p; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.01; nSweeps 1; } k { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.01; nSweeps 1; } omega { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.01; nSweeps 1; } epsilon { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.01; nSweeps 1; } } SIMPLE { nCorrectors 1; nNonOrthogonalCorrectors 3; consistent yes; } potentialFlow { nNonOrthogonalCorrectors 10; } relaxationFactors { equations { U 0.9; k 0.9; epsilon 0.9; } } cache { grad(U); } // ************************************************************************* // U Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { outlet { type pressureInletOutletVelocity; value uniform (0 0 0); } wall { type fixedValue; value $internalField; } inlet { type fixedValue; value uniform (-12 0 0); } } // ************************************************************************* // Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } wall { type zeroGradient; } } // ************************************************************************* // Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0.02; boundaryField { inlet { type fixedValue; value uniform 0.02; } outlet { type zeroGradient; } wall { type kqRWallFunction; value $internalField; } } // ************************************************************************* // Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -3 0 0 0 0]; internalField uniform 0.038; boundaryField { wall { type epsilonWallFunction; value $internalField; } inlet { type fixedValue; value $internalField; } outlet { type zeroGradient; } } // ************************************************************************* // Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -1 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type calculated; value uniform 0; } outlet { type calculated; value uniform 0; } wall { type nutkWallFunction; value uniform 0; } } // ************************************************************************* // Code:
Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 1768526 faces: 4478326 internal faces: 4058490 cells: 1368541 faces per cell: 6.2379 boundary patches: 4 point zones: 0 face zones: 0 cell zones: 1 Overall number of cells of each type: hexahedra: 1146266 prisms: 48425 wedges: 0 pyramids: 0 tet wedges: 93 tetrahedra: 0 polyhedra: 173757 Breakdown of polyhedra by number of faces: faces number of cells 4 26247 5 14342 6 20343 7 2 8 3 9 86303 10 12 12 18976 13 3 15 7379 18 147 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking basic patch addressing... Patch Faces Points wall 350661 378310 inlet 4354 4505 outlet 51327 51795 Checking geometry... Overall domain bounding box (-3.88806 -3.63696 -0.632848) (2 -0.04195 1.917) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (-1.95926e-016 -1.8415e-015 1.707e-016) OK. Max cell openness = 3.4469e-016 OK. Max aspect ratio = 7.21486 OK. Minimum face area = 2.51639e-006. Maximum face area = 0.00302785. Face area magnitudes OK. Min volume = 4.5284e-009. Max volume = 0.000163703. Total volume = 2.06708. Cell volumes OK. Mesh non-orthogonality Max: 62.0921 average: 10.7761 Non-orthogonality check OK. Face pyramids OK. Max skewness = 1.80749 OK. Coupled point location match (average 0) OK. Mesh OK. |
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