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[snappyHexMesh] How to create internal boundaries using snappyHexMesh |
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September 6, 2014, 14:38 |
How to create internal boundaries using snappyHexMesh
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#1 |
Member
Roberto Pieri
Join Date: Feb 2012
Location: Milan
Posts: 57
Rep Power: 14 |
Hi foamers,
I am trying to mesh a duct with zero-thickness deflectors in it. In the castellated phase snappy is able to refine cells near deflectors (as you can see in the attached figures below), but when running the snap phase, snappy doesn't morph the mesh following deflectors geometry. Moreover faceZones related to the deflectors are empty, as you can see below: Code:
Introducing zones for interfaces -------------------------------- Surface : deflettori_1 faceZone : deflettori_1 cellZone : deflettori_1 Surface : deflettori_2 faceZone : deflettori_2 cellZone : deflettori_2 Walking from location-in-mesh (12000 -18000 -22000) to assign cellZones - crossing a faceZone face changes cellZone Found point (12000 -18000 -22000) in global region 0 out of 1 regions. Only keeping zone faces inbetween different cellZones. CellZones: deflettori_1 size:0 deflettori_2 size:0 FaceZones: deflettori_1 size:0 deflettori_2 size:0 Edge intersection testing: Number of edges : 3596616 Number of edges to retest : 0 Number of intersected edges : 170194 Code:
/*--------------------------------*- C++ -*----------------------------------*| ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 2.2.0 | | \ / A nd | Web: www.OpenFOAM.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.2; format ascii; class dictionary; object autoHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; // true; snap true; // 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 { condotto.stl { type triSurfaceMesh; name condotto; patchInfo { type wall; } } deflettori_1.stl { type triSurfaceMesh; name deflettori_1; patchInfo { type wall; } } deflettori_2.stl { type triSurfaceMesh; name deflettori_2; patchInfo { type wall; } } }; // 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 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 10000000; // 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 0; // 1; // 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 6; // 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 "condotto.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 { condotto { // Surface-wise min and max refinement level level (2 2); } deflettori_1 { level (2 2); faceZone deflettori_1; // Create baffles for all faces on the surface faceType baffle; cellZone deflettori_1; cellZoneInside none; } deflettori_2 { level (2 2); faceZone deflettori_2; // Create baffles for all faces on the surface faceType baffle; cellZone deflettori_2; cellZoneInside none; } } resolveFeatureAngle 30; // 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 { } // 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 (12000 -18000 -22000); // 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 false; // true; (prima era true!) // false; } // Settings for the snapping. snapControls { //- Number of patch smoothing iterations before finding correspondence // to surface nSmoothPatch 3; // 3;(caso MidQ-meshMix) //- 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 4.0; // si puņ alzare... //- Number of mesh displacement relaxation iterations. nSolveIter 100; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; // Feature snapping //- 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 true; } // 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 { } // Expansion factor for layer mesh expansionRatio 1.2; //- 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 0.5; //- Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add layer. // See relativeSizes parameter. minThickness 0.002; //- 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 // make straight angle. featureAngle 180; //60 puis 180 //- 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 0.2; // 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 { //- Maximum non-orthogonality allowed. Set to 180 to disable. maxNonOrtho 65; // NB: mettere valore del checkMesh post castellated e separare 3 fasi //- Max skewness allowed. Set to <0 to disable. maxBoundarySkewness 4; maxInternalSkewness 2; //- 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 a sensible fraction of the smallest cell volume expected. // 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. Set to very negative number (e.g. -1E30) to // disable. // <0 = inside out tet, // 0 = flat tet // 1 = regular tet minTetQuality 1e-30; // ( prima era 1e-30: abilitato ); //- 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 0.05; // 0.05; // -1; disattivo //- minimum normalised cell determinant //- 1 = hex, <= 0 = folded or flattened illegal cell minDeterminant 0.001; //- minFaceWeight (0 -> 0.5) minFaceWeight 0.05; //- minVolRatio (0 -> 1) minVolRatio 0.01; //must be >0 for Fluent compatibility minTriangleTwist -1; //- if >0 : preserve single cells with all points on the surface if the // resulting volume after snapping (by approximation) is larger than // minVolCollapseRatio times old volume (i.e. not collapsed to flat cell). // If <0 : delete always. //minVolCollapseRatio 0.5; // Advanced //- Number of error distribution iterations nSmoothScale 4; //- amount to scale back displacement at error points errorReduction 0.75; // Optional : some meshing phases allow usage of relaxed rules. // See e.g. addLayersControls::nRelaxedIter. relaxed { //- Maximum non-orthogonality allowed. Set to 180 to disable. // maxNonOrtho 180; } } // 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; // ************************************************************************* // Thank you very much, Roberto |
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September 9, 2014, 13:31 |
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#2 |
Member
Roberto Pieri
Join Date: Feb 2012
Location: Milan
Posts: 57
Rep Power: 14 |
Any ideas??
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October 19, 2014, 10:57 |
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#3 |
Member
Cem Albukrek
Join Date: Mar 2009
Posts: 52
Rep Power: 17 |
Try to use the surface feature extraction feature on the missing sufraces. This comes with the latest 2.3 version of OpenFoam and seems to be fool proof. For an example you could look in the tutorials directory, i.e. Motorcycle case.
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