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July 17, 2012, 08:15 |
snappyHexMesh doesnt snap
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#1 |
New Member
Thomas
Join Date: Jul 2012
Location: Darmstadt
Posts: 7
Rep Power: 13 |
Hey Guys, i know you must be tired of this sort of question, but i havent found a similar case in this forum.
I am trying to create a mesh of a wall with several drillholes in it. The wall including the holes is a stl file, created with AutoCAD. When i run snappy, it refines the mesh but doesnt snap the cells to the stl surface, as you can see at the attached files. I tried to vary the refinement options (maybe too much cells), but that doesnt take effect. I am sure to look at the mesh at time "2". The Mesh of the bounding box is nearly cubic. Here are my blockMeshDict and snappyHexMeshDict: Code:
/*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.0 | | \\ / A nd | Web: http://www.openfoam.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; root ""; case ""; instance ""; local ""; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( (-10 0 0) (12.057 0 0) (12.057 72.8598 0) (-10 72.8598 0) (-10 0 6.6) (12.057 0 6.6) (12.057 72.8598 6.6) (-10 72.8598 6.6) ); blocks ( hex (0 1 2 3 4 5 6 7) (7 22 2) simpleGrading (1 1 1) ); edges ( ); boundary ( inlet { type patch; faces ( (0 4 7 3) ); } outlet { type patch; faces ( (1 2 6 5) ); } walls { type wall; faces ( (0 1 5 4) (0 3 2 1) (2 3 7 6) (4 5 6 7) ); } ); mergePatchPairs ( ); // ************************************************************************* // Code:
/*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.0 | | \\ / A nd | Web: http://www.openfoam.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; root "/home/penfold/mattijs/foam/mattijs2.1/run/icoFoam"; case "test2"; instance "system"; local ""; class dictionary; object autoHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; // true; snap true; // true; addLayers true; // 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 { test2.stl { type triSurfaceMesh; name stlSurface; } refinementBox { type searchableBox; min (0 0 0); max (0.5 0.5 0.5); } }; // Settings for the castellatedMesh generation. castellatedMeshControls { // Refinement parameters // ~~~~~~~~~~~~~~~~~~~~~ // While refining maximum number of cells per processor. This is basically // the number of cells that fit on a processor. If you choose this too small // it will do just more refinement iterations to obtain a similar mesh. maxLocalCells 1000000; // 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 2000000; // 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 2; // 2; // 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 "someLine.eMesh"; // level 2; //} ); // 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 { stlSurface { // Surface-wise min and max refinement level level (3 5); // 5 6 } } // Resolve sharp angles resolveFeatureAngle 15; // 30; // 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 { stlSurface { mode distance; levels ((0.1 5)(0.2 3)(1 2)); mode inside; // inside; levels ((1.0e+15 5)); //1E15 4 } }; // 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 (-5 0 3.3); // 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 2; //- Relative distance for points to be attracted by surface feature point // or edge. True distance is this factor times local // maximum edge length. tolerance 4; //- 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. // Do not use here since mesh resolution too low and baffles present //nFeatureSnapIter 10; } // Settings for the layer addition. addLayersControls { relativeSizes true; //true; // v 1.6 // Per final patch (so not geometry!) the layer information layers { //minZ //{ // nSurfaceLayers 3; //} stlSurface_patch0 // a_surface_name { nSurfaceLayers 5; } } // Expansion factor for layer mesh expansionRatio 1.4; // 1.0; //- 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. //finalLayerRatio FINALLAYERRATIO; // 0.3; finalLayerThickness 0.6; // 0.3; // v 1.6 //- 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. minThickness 0.001; // 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. nGrow 1; // 1; // Advanced settings //- When not to extrude surface. 0 is flat surface, 90 is when two faces // make straight angle. featureAngle 179; // 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 1; // Number of smoothing iterations of interior mesh movement direction 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 // v 1.6 nLayerIter 50; // v 1.6 } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { //- Maximum non-orthogonality allowed. Set to 180 to disable. maxNonOrtho ; //- Max skewness allowed. Set to <0 to disable. maxBoundarySkewness 20; maxInternalSkewness 4; //- Max concaveness allowed. Is angle (in degrees) below which concavity // is allowed. 0 is straight face, <0 would be convex face. // Set to 180 to disable. maxConcave 80; //- Minimum pyramid volume. Is absolute volume of cell pyramid. // Set to very negative number (e.g. -1E30) to disable. minVol 1e-13; //- Minimum quality of the tet formed by the face-centre // and variable base point minimum decomposition triangles and // the cell centre. This has to be a positive number for tracking // to work. Set to very negative number (e.g. -1E30) to // disable. // <0 = inside out tet, // 0 = flat tet // 1 = regular tet minTetQuality 1e-30; //- Minimum face area. Set to <0 to disable. minArea -1; //- Minimum face twist. Set to <-1 to disable. dot product of face normal //- and face centre triangles normal 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; // Merge tolerance. Is fraction of overall bounding box of initial mesh. // Note: the write tolerance needs to be higher than this. mergeTolerance 1E-6; // ************************************************************************* // |
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