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[snappyHexMesh] Not Able to Refine Mesh in Refinement Box |
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#1 |
New Member
Nian
Join Date: Jun 2019
Posts: 15
Rep Power: 7 ![]() |
Hello,
Sorry if this is a stupid question, but I have been stuck on trying to get a refinement box to work in the 'refinementRegions' settings for a few hours now, snappyHexMesh just ignores the refinementBox commands. I would really appreciate some help. ![]() I am using OpenFOAM 18.10, trying to 3D Mesh domain for an airfoil, and wishing to have a box of refinement region that could capture the flow around airfoil better. I have checked the searchableBox coordinates they should be okay, I have also increased maxLocalCells and maxGlobalCells so they should not be limiting the refinementBox meshing. I have tried meshing both with and without the "distance" mode for the airfoil surface under "refinementRegions", but snappyHexMesh still would not refine the targeted box region. The attached picture is a mid-slice through domain, the "distance mode" refinement around airfoil seems to be working. Below is my code for snappyHexMeshDict: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: dev | | \\ / 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 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 { airfoil { type triSurfaceMesh; file "airfoil.obj"; name surface0 } box { type searchableBox; min (-0.5 0.0 -1.5); max (2.0 2.0 1.5); } }; // 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 100000; // 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 8000000; // 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 20; // 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 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 "airfoil.eMesh"; level 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 { surface0 { // Surface-wise min and max refinement level level (5 6); // Optional specification of patch type (default is wall). No // constraint types (cyclic, symmetry) etc. are allowed. patchInfo { type wall; inGroups (airfoilGroup); } } } // Resolve sharp angles 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 { box { mode inside; levels ((1E15 3)); } surface0 { mode distance; levels ((0.1 5)(0.2 4)(0.4 3)); } } // 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 (2 2 2); // 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 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 2.0; //- Number of mesh displacement relaxation iterations. nSolveIter 30; //- 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 false; // Per final patch (so not geometry!) the layer information layers { surface0 { 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. firstLayerThickness 0.0003; // 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 0.000005; // 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 130; //60 // 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 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 // 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; } // 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; // ************************************************************************* // Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: dev | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; xmin -2.5; xmax 8.5; ymin 0; ymax 2; zmin -2.5; zmax 2.5; vertices ( ($xmin $ymin $zmin) ($xmax $ymin $zmin) ($xmax $ymax $zmin) ($xmin $ymax $zmin) ($xmin $ymin $zmax) ($xmax $ymin $zmax) ($xmax $ymax $zmax) ($xmin $ymax $zmax) ); blocks ( hex (0 1 2 3 4 5 6 7) (22 4 10) simpleGrading (1 1 1) ); edges ( ); boundary ( frontAndBack { type patch; faces ( (3 7 6 2) (1 5 4 0) ); } inlet { type patch; faces ( (0 4 7 3) ); } outlet { type patch; faces ( (2 6 5 1) ); } lowerWall { type wall; faces ( (0 3 2 1) ); } upperWall { type patch; faces ( (4 5 6 7) ); } ); // ************************************************************************* // ![]() |
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#2 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,169
Rep Power: 27 ![]() |
Hi,
It might just be a copy/paste problem but in your post, there is a missing semicolon here : Code:
airfoil { type triSurfaceMesh; file "airfoil.obj"; name surface0 } It should be : Code:
name surface0; This typo might prevent snappy from properly reading the "box" geometry. Let me know if it solves your problem. Yann |
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#3 | |
New Member
Nian
Join Date: Jun 2019
Posts: 15
Rep Power: 7 ![]() |
Quote:
Oh my goodness, this seems to be the reason, I am so mad for being stuck on this for so long hahaha. Thank you so much! It is working fine now. ![]() Nian |
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Tags |
mesh 3d, openfoam, snappyhexmesh |
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