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[snappyHexMesh] Patches disappearing after snappyHexMesh |
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October 25, 2018, 15:42 |
Patches disappearing after snappyHexMesh
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#1 |
Member
Obi
Join Date: Jul 2016
Location: Canada
Posts: 45
Rep Power: 10 |
I'm trying to do multiregion meshing using snappyHexMesh for a chtMultiRegionFoam simulation. I've tried to simplify the geometry to a totally cylinder enclosed by a square channel. But after running sHM, all my boundary conditions set for the channel zone disappears and i don't understand why.
Can anyone explain the reason for this? Here is my snappyHexMeshDict Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 4.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // //Dict file gotten from fillingOfTank tutorial 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 { channel { type triSurfaceMesh; file "channel.stl"; regions { inlet {name chInlet; } outlet {name chOutlet; } chanWalls {name chWalls; } } } cylWall { type triSurfaceMesh; file "cylinder3_1.stl"; } }; // 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 100000;//JN: for parallel meshing // 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;//JN: maximum number of cells - guiding value, can be exceeded // 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 4;//JN: number of cells between refinement levels // 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 "channel.eMesh"; level 2; } { file "cylinder3_1.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 { channel { level (0 2); faceZone chan; cellZone chan; cellZoneInside inside; regions { inlet {level (0 2); patchInfo { type patch; } } outlet {level (0 2); patchInfo { type patch; } } chanWalls {level (0 2); patchInfo { type wall; } } } } cylWall { level (0 2); faceZone cyl; cellZone cyl; cellZoneInside inside; } } resolveFeatureAngle 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 { //JN: here we could additionally refine the mesh } // 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. // This is an outside point locationInMesh (-0.033 -0.033 0.0033); locationInMesh (0.02 0.02 0.1); //JN: point inside our geometry // 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; } // Settings for the snapping. //JN: Mostly standard settings 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 1.0; //- Number of mesh displacement relaxation iterations. nSolveIter 300; //- 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) features by sampling the surface implicitFeatureSnap false; //- Use castellatedMeshControls::features explicitFeatureSnap true; //- Detect features between multiple surfaces // (only for explicitFeatureSnap, default = false) 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 { cylWall { nSurfaceLayers 5; } chanWalls { nSurfaceLayers 5; } } // Expansion factor for layer mesh expansionRatio 1.1; // 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. // See relativeSizes parameter. finalLayerThickness 0.3; // Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add 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. nGrow 0; // Advanced settings // When not to extrude surface. 0 is flat surface, 90 is when two faces // are perpendicular featureAngle 90; // 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 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" // 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 75; } // Advanced //- Number of error distribution iterations nSmoothScale 4; //- Amount to scale back displacement at error points errorReduction 0.75; } // Advanced debug 0; // Write flags writeFlags ( scalarLevels // write volScalarField with cellLevel for postprocessing layerSets // write cellSets, faceSets of faces in layer layerFields // write volScalarField for layer coverage ); // 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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October 26, 2018, 06:03 |
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#2 | |
Member
ssa
Join Date: Sep 2018
Posts: 93
Rep Power: 8 |
Quote:
I think you should not specify patches in snappy. |
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October 26, 2018, 13:01 |
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#3 |
Member
Obi
Join Date: Jul 2016
Location: Canada
Posts: 45
Rep Power: 10 |
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April 14, 2023, 14:24 |
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#4 |
Member
Nevada
Join Date: Apr 2014
Posts: 32
Rep Power: 12 |
Hi, Did you get a solution for this issue? I get inner mapped wall if I do low level of snap but when I increase the level it removes the inner wall. Why is it so sensitive? Is it supposed to be?
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