September 15, 2011, 08:02
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Boundary layer in a pipe
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#1
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New Member
clement
Join Date: May 2011
Location: München
Posts: 12
Rep Power: 15
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Hi OpenFOAMer,
I'm actually trying to mesh a cabin for a HVAC problem with the SHM. But after a lot of attempts I don't succed in creating my boundary layer in the entire pipe system. You will find enclosed a cross section of the pipe and a copy of my SHMdict file. You will see that when the curvature of my pipe increase, the BL desappear.
If somebody get an idea .... I allready read a lot of topic on the subject but found any explanation.
Thanks
Clement
PHP Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.7.0 | | \\ / A nd | Web: www.OpenFOAM.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh 1; snap 1; addLayers 1;
// 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 { inlet.stl{ type triSurfaceMesh; name inlet;} outlet.stl{ type triSurfaceMesh; name outlet;} pipe.stl{ type triSurfaceMesh; name pipe;} inlay.stl{ type triSurfaceMesh; name inlay;} cabin-roof.stl{ type triSurfaceMesh; name cabin-roof;} cabin-side.stl{ type triSurfaceMesh; name cabin-side;} cabin-front.stl{ type triSurfaceMesh; name cabin-front;} cabin-floor.stl{ type triSurfaceMesh; name cabin-floor;} cabin-back.stl{ type triSurfaceMesh; name cabin-back;} refine-roof.stl{ type triSurfaceMesh; name refine-roof;} refine-panel-top.stl{ type triSurfaceMesh; name refine-panel-top;} panel.stl{ type triSurfaceMesh; name panel;} };
// 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 200000000;
// 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 200000000;
// 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 2000;
// 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 0.1;
// Number of buffer layers between different levels. // 1 means normal 2:1 refinement restriction, larger means slower // refinement. nCellsBetweenLevels 5;
// 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 "inlet.eMesh"; level 3; } { file "outlet.eMesh"; level 3; } { file "pipe.eMesh"; level 3; } { file "inlay.eMesh"; level 3; } { file "cabin-roof.eMesh"; level 3; } { file "cabin-side.eMesh"; level 3; } { file "cabin-front.eMesh"; level 3; } { file "cabin-floor.eMesh"; level 3; } { file "cabin-back.eMesh"; level 3; } { file "refine-roof.eMesh"; level 3; } { file "refine-panel-top.eMesh"; level 3; } { file "panel.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 { inlet{ // Surface-wise min and max refinement level level (5 5);} outlet{ // Surface-wise min and max refinement level level (1 1);} pipe{ // Surface-wise min and max refinement level level (5 5);} inlay{ // Surface-wise min and max refinement level level (6 6);} cabin-roof{ // Surface-wise min and max refinement level level (1 1);} cabin-side{ // Surface-wise min and max refinement level level (1 1);} cabin-front{ // Surface-wise min and max refinement level level (1 1);} cabin-floor{ // Surface-wise min and max refinement level level (1 1);} cabin-back{ // Surface-wise min and max refinement level level (1 1);} refine-roof{ // Surface-wise min and max refinement level level (6 6);} refine-panel-top{ // Surface-wise min and max refinement level level (6 6);} panel{ // Surface-wise min and max refinement level level (1 1);} }
// Resolve sharp angles resolveFeatureAngle 10;
// 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 (-1864.72 574.182 2774.74);
// 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 5;
//- 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 15;
//- Highly experimental and wip: number of feature edge snapping // iterations. Leave out altogether to disable. nFeatureSnapIter 20; }
// 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 { inlet_inlet{ nSurfaceLayers 2;}; pipe_pipe{ nSurfaceLayers 2;}; inlay_inlay{ nSurfaceLayers 2;}; refine-roof_refine-roof{ nSurfaceLayers 2;}; refine-panel-top_refine-panel-top{ nSurfaceLayers 2;}; }
// 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 0.8;
//- Minimum thickness of cell layer. If for any reasn layer // cannot be above minThickness do not add layer. // Relative to undistorted size of cell outside layer. minThickness 0.05;
//- 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 // make straight angle. featureAngle 30;
//- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 20;
// Number of smoothing iterations of surface normals nSmoothSurfaceNormals 20;
// Number of smoothing iterations of interior mesh movement direction nSmoothNormals 20;
// Smooth layer thickness over surface patches nSmoothThickness 10;
// Stop layer growth on highly warped cells maxFaceThicknessRatio 0.1;
// Reduce layer growth where ratio thickness to medial // distance is large maxThicknessToMedialRatio 0.05;
// Angle used to pick up medial axis points minMedianAxisAngle 60;
// Create buffer region for new layer terminations nBufferCellsNoExtrude 0;
// Overall max number of layer addition iterations nLayerIter 120;
nRelaxedIter 60; }
// 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;
//- Max skewness allowed. Set to <0 to disable. maxBoundarySkewness 20; maxInternalSkewness 4;
//- 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 projected area v.s. actual area. Set to -1 to disable. minFlatness 0.5;
//- 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-06;
//- Minimum quality of the tet formed by the face-centre // and variable base point minimum decomposition triangles and // the cell centre. This has to be a positive number for tracking // to work. Set to very negative number (e.g. -1E30) to // disable. // <0 = inside out tet, // 0 = flat tet // 1 = regular tet minTetQuality 1e-9;
//- Minimum face area. Set to <0 to disable. minArea 0.0001;
//- Minimum face twist. Set to <-1 to disable. dot product of face normal //- and face centre triangles normal minTwist 0.02;
//- minimum normalised cell determinant //- 1 = hex, <= 0 = folded or flattened illegal cell minDeterminant 0.001;
//- minFaceWeight (0 -> 0.5) minFaceWeight 0.02;
//- minVolRatio (0 -> 1) minVolRatio 0.01;
//must be >0 for Fluent compatibility minTriangleTwist -1;
// Advanced
//- Number of error distribution iterations nSmoothScale 4; //- amount to scale back displacement at error points errorReduction 0.75; }
// 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;
// ************************************************************************* //
[IMG]file:///tmp/moz-screenshot.png[/IMG]
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