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[snappyHexMesh] SnappyHexMEsh Surface Refinement |
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August 29, 2011, 05:21 |
SnappyHexMEsh Surface Refinement
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#1 |
New Member
Levent Aymelek
Join Date: Aug 2011
Posts: 12
Rep Power: 14 |
Hi all,
I am trying to mesh a domain using SnappyHexMesh. After meshing is succesfully completed i checked the mesh and some part of the surfaces are not refined althoug other did... i attach my snappyhexmeshdict and add a screenshot of the mesh. Does someone have any idea what can be the reason? /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.7.1 | | \\ / A nd | Web: www.OpenFOAM.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; snap false; addLayers false; geometry { simple.stl { convertToMeters 1; type triSurfaceMesh; name simple; } refinementBox { type searchableBox; min (-50 -300 -300); max ( 50 300 300); } }; // Settings for the castellatedMesh generation. castellatedMeshControls { // Refinement parameters // ~~~~~~~~~~~~~~~~~~~~~ maxLocalCells 1000000; maxGlobalCells 2000000; minRefinementCells 10; maxLoadUnbalance 0.10; nCellsBetweenLevels 3; // Explicit feature edge refinement // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ features ( //{ // file "someLine.eMesh"; // level 2; //} ); // Surface based refinement // ~~~~~~~~~~~~~~~~~~~~~~~~ refinementSurfaces { simple { // Surface-wise min and max refinement level level (5 6); } } // Resolve sharp angles resolveFeatureAngle 10; // Region-wise refinement // ~~~~~~~~~~~~~~~~~~~~~~ refinementRegions { refinementBox { mode inside; levels ((3 2)); } } // Mesh selection // ~~~~~~~~~~~~~~ locationInMesh (-50 -500 -500); } // Settings for the snapping. snapControls { nSmoothPatch 3; tolerance 4.0; //- Number of mesh displacement relaxation iterations. nSolveIter 30; nRelaxIter 5; } // Settings for the layer addition. addLayersControls { relativeSizes true; layers { } // Expansion factor for layer mesh expansionRatio 1.0; finalLayerThickness 0.3; minThickness 0.1; nGrow 1; // Advanced settings featureAngle 30; nRelaxIter 3; // Number of smoothing iterations of surface normals nSmoothSurfaceNormals 1; nSmoothNormals 3; // Smooth layer thickness over surface patches nSmoothThickness 10; // Stop layer growth on highly warped cells maxFaceThicknessRatio 0.5; // Reduce layer growth where ratio thickness to medial // distance is large maxThicknessToMedialRatio 0.3; // Angle used to pick up medial axis points minMedianAxisAngle 130; // Create buffer region for new layer terminations nBufferCellsNoExtrude 0; // Overall max number of layer addition iterations nLayerIter 50; } meshQualityControls { maxNonOrtho 65; maxBoundarySkewness 20; maxInternalSkewness 4; maxConcave 80; minFlatness 0.5; minVol 1e-13; minArea -1; minTwist 0.02; //- minimum normalised cell determinant //- 1 = hex, <= 0 = folded or flattened illegal cell minDeterminant 0.001; //- minFaceWeight (0 -> 0.5) minFaceWeight 0.02; //- minVolRatio (0 -> 1) minVolRatio 0.01; //must be >0 for Fluent compatibility minTriangleTwist -1; // Advanced //- Number of error distribution iterations nSmoothScale 4; //- amount to scale back displacement at error points errorReduction 0.75; } // Advanced // Flags for optional output // 0 : only write final meshes // 1 : write intermediate meshes // 2 : write volScalarField with cellLevel for postprocessing // 4 : write current intersections as .obj files debug 0; mergeTolerance 1E-6; // ************************************************** *********************** // |
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August 29, 2011, 05:29 |
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#2 |
Senior Member
Roman Thiele
Join Date: Aug 2009
Location: Eindhoven, NL
Posts: 374
Rep Power: 20 |
did you check that you didn't run into the problem of maximum reached cells? try changing the maximum cells you can have and/or reducing the level to which you refine around surfaces, say (3 4).
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~roman |
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August 29, 2011, 06:28 |
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#3 |
New Member
Levent Aymelek
Join Date: Aug 2011
Posts: 12
Rep Power: 14 |
Hi,
thanks for reply. I checked the number of cells.. its around 700k. still under the limit. But thge strange thing happened.. i deleted all the time steps and meshed again it seems like its working now... but i dont understand i did it lots of times and it was always the same problematic mesh but know its meshing quite well..... Thanks a lot! |
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August 29, 2011, 06:32 |
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#4 | |
Senior Member
Roman Thiele
Join Date: Aug 2009
Location: Eindhoven, NL
Posts: 374
Rep Power: 20 |
Quote:
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~roman |
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August 29, 2011, 07:05 |
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#5 |
New Member
Levent Aymelek
Join Date: Aug 2011
Posts: 12
Rep Power: 14 |
OK! Now its great info... i will check again. Thanks a lot
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August 29, 2011, 09:46 |
addLayers
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#6 |
Senior Member
Jon Elvar Wallevik
Join Date: Nov 2010
Location: Reykjavik, ICELAND
Posts: 103
Rep Power: 19 |
Hi laymelek
I would also recommend that you have snap true; addLayers true; with the latter you have to have layers { simple { nSurfaceLayers 3; } } the number 3 is just an example (I usually use this). Note that the name simple in the above might have to be changed, depending on the name of solid in the stl file is. For example if the designation is "solid voff_2" (edit the stl file and you see this in the first line) and the name of the .stl file is simple.stl, then use layers { simple_voff_2 ... And final comment. Often, my simulation have crashed when using snappy. To solve this is to have small cells in vicinity of wall to handle large grad(U). This means large refinement at surface, say 4 to 5. Hope this helps |
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August 29, 2011, 09:56 |
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#7 |
Member
Join Date: Nov 2009
Location: Germany
Posts: 96
Rep Power: 16 |
Hi,
Well, surface refinement 4 to 5 says nothing about how fine the mesh is. Have you looked at the yplus values? Maybe you could correlate the yplus values with the crashed simulation? This would be very interesting to me.
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"When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." Werner Heisenberg
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August 29, 2011, 10:08 |
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#8 |
Senior Member
Jon Elvar Wallevik
Join Date: Nov 2010
Location: Reykjavik, ICELAND
Posts: 103
Rep Power: 19 |
Sorry, I am not using turbulence modeling. My theme is usually non Newt fluid mech, like the HB modell.
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