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[snappyHexMesh] very bad quality snapped mesh |
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July 11, 2016, 09:35 |
very bad quality snapped mesh
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Member
Federica Biano
Join Date: Feb 2016
Location: Genova, Italy
Posts: 39
Rep Power: 10 |
Hi everyone!
I'm trying to create a mesh with snappyHexMesh in OF 3.0.1 and I'm having lots of troubles with the snapping procedure. The mesh I obtain has a very poor quality, it isn't snapped at all and I don't know why. I used the same settings on other geometries and they worked. I attach my stl geometry, the dictionary used and the images of the result. SnappyHexMeshDict Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.3.0 | | \\ / 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 false; // 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 { meshInteraNeww.stl { type triSurfaceMesh; name meshInteraNeww; patchInfo { type wall; } } refinementBox1 { type searchableBox; min (-0.4 0 -2.4); max (27.2 3.8 4.8); } /* refinementBoxI1 { type searchableBox; min (0 0 -0.4); max (60 5 0.4); } refinementBoxS { type searchableBox; min (-10 0 -1.5); max (1 5 0.5); } */ }; // 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 10000000; // 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 20000000; // 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; // Number of buffer layers between different levels. // 1 means normal 2:1 refinement restriction, larger means slower // refinement. nCellsBetweenLevels 5; // 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 "meshInteraNeww.eMesh"; level 6; // 5 3 } ); // 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 { meshInteraNeww { // Surface-wise min and max refinement level level (6 6); // 5 5 } } resolveFeatureAngle 25; // 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 { refinementBox1 { mode inside; // inside; levels ((1E15 6)); //1E15 4 } /* refinementBoxI1 { mode inside; // inside; levels ((1E15 6)); //1E15 4 } refinementBoxS { mode inside; // inside; levels ((1E15 6)); //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 (-4.5 30 0.5); // 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 4; //- Relative distance for points to be attracted by surface feature point // or edge. True distance is this factor times local // maximum edge length. // tolerance 4.0; tolerance 6; //- Number of mesh displacement relaxation iterations. nSolveIter 400; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 10; nFeatureSnapIter 10; // Detect (geometric only) features by sampling the surface // (default=false). implicitFeatureSnap true; //- 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 { meshInteraNeww { nSurfaceLayers 3; // 3 } } // Expansion factor for layer mesh expansionRatio 1.5; // 1.5 // Wanted thickness of final added cell layer. If multiple layers // is the thickness of the layer furthest away from the wall. // See relativeSizes parameter. finalLayerThickness 0.1; // 0.7 // Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add layer. // See relativeSizes parameter. minThickness 0.001; // 0.25 // 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 60; // Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; // 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 // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x. 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 50; // Max number of iterations after which relaxed meshQuality controls // get used. Up to nRelaxIter it uses the settings in meshQualityControls, // after nRelaxIter it uses the values in meshQualityControls::relaxed. nRelaxedIter 20; } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { #include "meshQualityDict" } // 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; // ************************************************************************* // Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.3.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object surfaceFeatureExtractDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // meshInteraNeww.stl { // How to obtain raw features (extractFromFile || extractFromSurface) extractionMethod extractFromSurface; extractFromSurfaceCoeffs { // Mark edges whose adjacent surface normals are at an angle less // than includedAngle as features // - 0 : selects no edges // - 180: selects all edges includedAngle 175; } subsetFeatures { // Keep nonManifold edges (edges with >2 connected faces) nonManifoldEdges yes; // Keep open edges (edges with 1 connected face) openEdges yes; } // Write options // Write features to obj format for postprocessing writeObj yes; } // ************************************************************************* // Best regards Federica |
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