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[snappyHexMesh] strange form of cells near refinementzone |
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March 5, 2017, 19:03 |
strange form of cells near refinementzone
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#1 |
New Member
Join Date: Nov 2016
Posts: 8
Rep Power: 9 |
Hello together,
I'm trying to simulate an open channel flow with interFoam, using openFoam version 4.1. After meshing with snappyHexMesh i get a strange looking Mesh at the inside of my geometry (picture attached). When looking from outside at the surface everything seems fine. You'll find my snappyHexMeshDict attached... Any hints would help me a lot, i'm under a great pressure of time and won't find the mistake! Thanks a lot!!! 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 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; // make basic mesh ? snap true; // decide to snap back to surface ? addLayers false; // decide to add viscous layers ? geometry // Load in STL files here { Spundwand.stl {type triSurfaceMesh; name Spundwand;} Aussenwand.stl {type triSurfaceMesh; name Aussenwand;} refinementBox {type searchableBox; min (-1 -1 -1); max (10 10 10);} }; castellatedMeshControls { maxLocalCells 10000000; //max cells per CPU core maxGlobalCells 20000000; //max cells to use before mesh deletion step minRefinementCells 10; //was 0 - zero means no bad cells are allowed during refinement stages maxLoadUnbalance 0.10; nCellsBetweenLevels 1; // expansion factor between each high & low refinement zone // Explicit feature edge refinement // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ features // taken from STL from each .eMesh file created by "SurfaceFeatureExtract" command ( {file "Aussenwand.eMesh"; level 1;} {file "Spundwand.eMesh"; level 1;} ); // Surface based refinement // ~~~~~~~~~~~~~~~~~~~~~~~~ refinementSurfaces // Surface-wise min and max refinement level { Aussenwand {level (3 3);} Spundwand {level (3 3);} } resolveFeatureAngle 80; // Resolve sharp angles // Default 30 refinementRegions // In descending levels of fine-ness { Spundwand { mode distance; levels ((0.0125 3)); // was ((0.001 4) (0.003 3) (0.01 2)) } Aussenwand { mode distance; levels ((0.0125 3)); // was ((0.001 4) (0.003 3) (0.01 2)) } } locationInMesh (1.1 1.1 1.1); //to decide which side of mesh to keep ** allowFreeStandingZoneFaces false; } // Settings for the snapping. snapControls { nSmoothPatch 3; tolerance 4.0; nSolveIter 30; nRelaxIter 5; nFeatureSnapIter 15; // default is 10 // New settings from openfoam 2.2 onwards for SHMesh implicitFeatureSnap false; // default is false - detects without doing surfaceFeatureExtract explicitFeatureSnap true; // default is true multiRegionFeatureSnap false; // deafault is false - detects features between multiple surfaces } // Settings for the layer addition. //nicht nötig wenn oben false addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName { relativeSizes false; // was true layers { Aussenwand {nSurfaceLayers 1;} // was 3 Spundwand {nSurfaceLayers 1;} // was 3 } expansionRatio 1.3; finalLayerThickness 0.00016; //was 0.00016 minThickness 0.00008; //was 0.00008 nGrow 0; // was 1 // Advanced settings featureAngle 80; // was 70 //- When not to extrude surface. 0 is flat, 90 is right angle. nRelaxIter 3; //- Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh. nSmoothSurfaceNormals 1; // Number of smoothing iterations of surface normals nSmoothNormals 3; // Number of smoothing iterations of interior mesh movement direction nSmoothThickness 10; // Smooth layer thickness over surface patches maxFaceThicknessRatio 0.5; // Stop layer growth on highly warped cells maxThicknessToMedialRatio 0.3; // Reduce layer growth where ratio thickness to medial distance is large minMedianAxisAngle 130; // Angle used to pick up medial axis points nBufferCellsNoExtrude 0; // Create buffer region for new layer terminations nLayerIter 50; // Overall max number of layer addition iterations } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { maxNonOrtho 65; maxBoundarySkewness 20; maxInternalSkewness 4; maxConcave 80; minFlatness 0.5; minVol 1e-13; minTetQuality 1e-9; minArea -1; minTwist 0.02; minDeterminant 0.001; minFaceWeight 0.02; minVolRatio 0.01; minTriangleTwist -1; // Advanced nSmoothScale 4; errorReduction 0.75; } // Advanced 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; // ************************************************************************* // |
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March 5, 2017, 22:08 |
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#2 |
Senior Member
Join Date: Aug 2013
Posts: 407
Rep Power: 15 |
Hi,
If I am not mistaken, your second image (the one in grey) is a slice/clip. If so, there isn't anything wrong with your mesh, at least nothing that is discernible from the images. You have refinementRegions which lead to polyhedral cells which are shown by Paraview that way. When you load up the .foam file (I assume that is how you are viewing the mesh), uncheck the "Decompose Polyhedra" option and your mesh should look fine. Hope this helps. Cheers, Antimony |
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March 6, 2017, 07:05 |
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#3 |
New Member
Join Date: Nov 2016
Posts: 8
Rep Power: 9 |
Hello Antimony,
thanks a lot for the quick and helpful reply! Got it, looks much better. Greetings Robert |
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