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[snappyHexMesh] Layers in snappy collapse in some places of my solid |
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March 8, 2015, 16:44 |
Layers in snappy collapse in some places of my solid
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#1 |
Member
Rubén
Join Date: Oct 2014
Location: Munich
Posts: 47
Rep Power: 12 |
Hi FOAMers!
I am having an issue with snappyhexmesh. I have looked in this posts: http://www.cfd-online.com/Forums/ope...d-surface.html http://www.cfd-online.com/Forums/ope...ng-layers.html But, they doesn't work for me You can see in my first picture a slice of the internal mesh in the mid plane. As you can see, layers are added without a problem. But, if I move the slice a little bit, you can see that layers have collapsed, and they dissapear I have changed every number on the addlayer part of snappyhexmeshdict... I really don't know what to do I attach my snappyhexmeshdict file: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; snap true; addLayers true; // Geometry. Definition of all surfaces. All surfaces are of class // searchableSurface. // Surfaces are used // - to specify refinement for any mesh cell intersecting it // - to specify refinement for any mesh cell inside/outside/near // - to 'snap' the mesh boundary to the surface geometry { frisbee.stl { type triSurfaceMesh; name frisbee; } refinementBox0 { type searchableBox; min (-0.135 -0.135 -0.07); max (0.135 0.135 0.0015); } refinementBox1 { type searchableBox; min (0.135 -0.07 -0.07); max (0.6 0.04 0.02); } refinementBox2 { type searchableBox; min (0.13 -0.1 -0.05); max (1.5 0.07 0.05); } refinementBox3 { type searchableBox; min (-0.3 -0.2 -0.1); max (3 0.2 0.1); } refinementBox4 { type searchableBox; min (-0.45 -0.25 -0.12); max (4.5 0.25 0.12); } }; // Settings for the castellatedMesh generation. castellatedMeshControls { // Refinement parameters // ~~~~~~~~~~~~~~~~~~~~~ // If local number of cells is >= maxLocalCells on any processor // switches from from refinement followed by balancing // (current method) to (weighted) balancing before refinement. maxLocalCells 640000; // Overall cell limit (approximately). Refinement will stop immediately // upon reaching this number so a refinement level might not complete. // Note that this is the number of cells before removing the part which // is not 'visible' from the keepPoint. The final number of cells might // actually be a lot less. maxGlobalCells 6400000; // The surface refinement loop might spend lots of iterations refining just // a few cells. This setting will cause refinement to stop if <= // minimumRefine are selected for refinement. Note: it will at least do one // iteration (unless the number of cells to refine is 0) minRefinementCells 10; // Allow a certain level of imbalance during refining // (since balancing is quite expensive) // Expressed as fraction of perfect balance (= overall number of cells / // nProcs). 0=balance always. maxLoadUnbalance 0.10; // Number of buffer layers between different levels. // 1 means normal 2:1 refinement restriction, larger means slower // refinement. nCellsBetweenLevels 3; // Explicit feature edge refinement // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // Specifies a level for any cell intersected by its edges. // This is a featureEdgeMesh, read from constant/triSurface for now. features ( { file "frisbee.eMesh"; level 6; } ); // Surface based refinement // ~~~~~~~~~~~~~~~~~~~~~~~~ // Specifies two levels for every surface. The first is the minimum level, // every cell intersecting a surface gets refined up to the minimum level. // The second level is the maximum level. Cells that 'see' multiple // intersections where the intersections make an // angle > resolveFeatureAngle get refined up to the maximum level. refinementSurfaces { frisbee { // Surface-wise min and max refinement level level (7 9); } } // Resolve sharp angles on fridges resolveFeatureAngle 60; // Region-wise refinement // ~~~~~~~~~~~~~~~~~~~~~~ // Specifies refinement level for cells in relation to a surface. One of // three modes // - distance. 'levels' specifies per distance to the surface the // wanted refinement level. The distances need to be specified in // descending order. // - inside. 'levels' is only one entry and only the level is used. All // cells inside the surface get refined up to the level. The surface // needs to be closed for this to be possible. // - outside. Same but cells outside. refinementRegions { frisbee { mode distance; levels ((0.008 10)); } refinementBox0 { mode inside; levels ((1e15 9)); } refinementBox1 { mode inside; levels ((1e15 9)); } refinementBox2 { mode inside; levels ((1e15 7)); } refinementBox3 { mode inside; levels ((1e15 4)); } refinementBox4 { mode inside; levels ((1e15 2)); } } // Mesh selection // ~~~~~~~~~~~~~~ // After refinement patches get added for all refinementSurfaces and // all cells intersecting the surfaces get put into these patches. The // section reachable from the locationInMesh is kept. // NOTE: This point should never be on a face, always inside a cell, even // after refinement. locationInMesh (0 0 0); // Whether any faceZones (as specified in the refinementSurfaces) // are only on the boundary of corresponding cellZones or also allow // free-standing zone faces. Not used if there are no faceZones. allowFreeStandingZoneFaces true; } // Settings for the snapping. snapControls { //- Number of patch smoothing iterations before finding correspondence // to surface nSmoothPatch 3; //- Relative distance for points to be attracted by surface feature point // or edge. True distance is this factor times local // maximum edge length. tolerance 2.0; //- Number of mesh displacement relaxation iterations. nSolveIter 30; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; //- Highly experimental and wip: number of feature edge snapping // iterations. Leave out altogether to disable. nFeatureSnapIter 10; //- Detect (geometric only) features by sampling the surface // (default=false). implicitFeatureSnap false; //- Use castellatedMeshControls::features (default = true) explicitFeatureSnap true; //- Detect points on multiple surfaces (only for explicitFeatureSnap) multiRegionFeatureSnap false; } // Settings for the layer addition. addLayersControls { // Are the thickness parameters below relative to the undistorted // size of the refined cell outside layer (true) or absolute sizes (false). relativeSizes true; // Per final patch (so not geometry!) the layer information layers { "frisbee.*" { nSurfaceLayers 5; } } // Expansion factor for layer mesh expansionRatio 1.15; //- Wanted thickness of final added cell layer. If multiple layers // is the // thickness of the layer furthest away from the wall. // Relative to undistorted size of cell outside layer. // is the thickness of the layer furthest away from the wall. // See relativeSizes parameter. finalLayerThickness 0.3; //- Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add layer. // Relative to undistorted size of cell outside layer. // See relativeSizes parameter. minThickness 0.1; //- If points get not extruded do nGrow layers of connected faces that are // also not grown. This helps convergence of the layer addition process // close to features. // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x) nGrow 0; // Advanced settings // When not to extrude surface. 0 is flat surface, 90 is when two faces // are perpendicular featureAngle 360; // At non-patched sides allow mesh to slip if extrusion direction makes // angle larger than slipFeatureAngle. slipFeatureAngle 30; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 3; // Number of smoothing iterations of surface normals nSmoothSurfaceNormals 50; // Number of smoothing iterations of interior mesh movement direction nSmoothNormals 50; // Smooth layer thickness over surface patches nSmoothThickness 100; // Stop layer growth on highly warped cells maxFaceThicknessRatio 1.4; // Reduce layer growth where ratio thickness to medial // distance is large maxThicknessToMedialRatio 1.2; // Angle used to pick up medial axis points // Note: changed(corrected) w.r.t 16x! 90 degrees corresponds to 130 in 16x. minMedianAxisAngle 90; // Create buffer region for new layer terminations nBufferCellsNoExtrude 0; // Overall max number of layer addition iterations. The mesher will exit // if it reaches this number of iterations; possibly with an illegal // mesh. nLayerIter 300; } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { #include "meshQualityDict" // Advanced //- Number of error distribution iterations nSmoothScale 4; //- amount to scale back displacement at error points errorReduction 0.75; // 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; // Merge tolerance. Is fraction of overall bounding box of initial mesh. // Note: the write tolerance needs to be higher than this. mergeTolerance 1e-6; // ************************************************************************* // Snappy takes a lot of time to be understood, I have been working for months with it... and I have to finish my thesis |
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