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[snappyHexMesh] SnappyHexMesh creates me unnecessary patch if I try to refine my surfaces |
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March 7, 2024, 06:50 |
SnappyHexMesh creates me unnecessary patch if I try to refine my surfaces
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Luca Fanchini
Join Date: Feb 2024
Posts: 3
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Dear all I'm facing a problem... I'm trying to mesh a pipe inside a plate using snappyHexMesh.
I created my stl files using Inventor and I did the triangulation of the Stls using Salome. I exported the stl files in Ascii code in order to rename the patches. The problem is ... If I create a coarse mesh I obtain the patches I want: inlet, outlet, wall, wallOI and Pipe_to_Coolant (interface patch). If I try to refine the mesh at level (2 2) SnappyHexMesh creates me an additional patch called pipe... Also if I try to snap the patches are created. I don't know if it will damage the results of the simulation. Does anyone have a solution in order to cancel the additional patch? I attach images. This is the SnappyHexMeshDict: // Which of the steps to run castellatedMesh 1; snap 0; addLayers 0; // 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 { coolant { type triSurfaceMesh; file "assieme.stl"; regions { inlet {name inlet;} outlet {name outlet;} wall {name wall;} wallInletOutlet { name wallOI; } } } pipe { type triSurfaceMesh; file "interface.stl"; } wall { type triSurfaceMesh; file "wall.stl"; } wallInletOutlet { type triSurfaceMesh; file "wallInletOutlet.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 2000000; // 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 6; // 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 0.0; // Number of buffer layers between different levels. // 1 means normal 2:1 refinement restriction, larger means slower // refinement. nCellsBetweenLevels 4; // 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 "assieme.eMesh"; level 1; } { file "interface.eMesh"; level 1; } { file "wall.eMesh"; level 1; } { file "wallInletOutlet.eMesh"; level 1; } ); // 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 { coolant { level (1 1); regions { wall {level (1 1); patchInfo { type wall; }} wallInletOutlet {level (1 1); patchInfo { type wall; }} } } pipe { level (1 1); regions { inlet {level (1 1); patchInfo { type patch; }} outlet {level (1 1); patchInfo { type patch; }} } } } // Resolve sharp angles 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 { } // 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. locationsInMesh ( (( -0.15 0 -0.015) Pipe) (( 0 0.009 -0.015) Coolant) ); // 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 thekqRWallFunction;re 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 1.5; //- Number of mesh displacement relaxation iterations. nSolveIter 15; //- 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 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 { pipe { nSurfaceLayers 10; } coolant { nSurfaceLayers 6; } } // Expansion factor for layer mesh expansionRatio 1.05; // 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 0.6; // 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 0.4; // 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 1.7.x! (didn't do anything in 1.7.x) nGrow 0; // Advanced settings // When not to extrude surface. 0 is flat surface, 90 is when two faces // are perpendicular featureAngle 90; // 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 6; // Number of smoothing iterations of surface normals nSmoothSurfaceNormals 2; // Number of smoothing iterations of interior mesh movement direction nSmoothNormals 6; // Smooth layer thickness over surface patches nSmoothThickness 20; // 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 1.7.x! 90 degrees corresponds to 130 // in 1.7.x. minMedialAxisAngle 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 100; } // 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 // Write flags writeFlags ( scalarLevels layerSets 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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