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-   -   [snappyHexMesh] snappyHexMesh does weird stuff sometimes (https://www.cfd-online.com/Forums/openfoam-meshing/169188-snappyhexmesh-does-weird-stuff-sometimes.html)

louay-tud April 5, 2016 03:36

snappyHexMesh does weird stuff sometimes
 
1 Attachment(s)
Hallo everyone, I've just a problem with the Mesh rsults of SnappyHexMesh. I've worked on mehsing of a complex geometry. Snappy did well but there's something wrong with the mesh and i can't get rid of it. when you guys look at the attached photo, where my red circle is. why did Snappy did this cells inclined and not vertical like their neighbours. Has anybody a clarification for this issue? Thank you very much

here is my SnappyHexMeshDict as well:
/*--------------------------------*- 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
{
Innenteil.stl {type triSurfaceMesh; name Innenteil;}
refinementBox {type searchableBox; min (-0.6 -0.08 -0.5); max (0.6 0.08 0.5);}
};

castellatedMeshControls
{
maxLocalCells 1000000; //max cells per CPU core
maxGlobalCells 3500000; //max cells to use before mesh deletion step
minRefinementCells 5; //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 "Innenteil.eMesh";
levels ((0.0 2)(0.00003 1));
}
);

// Surface based refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~

refinementSurfaces // Surface-wise min and max refinement level
{
Innenteil {level (5 5);}
}


resolveFeatureAngle 30; // Resolve sharp angles // Default 80
refinementRegions // In descending levels of fine-ness
{Innenteil {mode distance; levels ((0.006 4) (0.02 3) (0.1 2));}}
locationInMesh (1.51 -0.72 0.45); //to decide which side of mesh to keep **
allowFreeStandingZoneFaces false;
}


// Settings for the snapping.
snapControls
{
nSmoothPatch 3;
tolerance 4.0;
nSolveIter 200;
nRelaxIter 15;
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 true; // deafault is false - detects features between multiple surfaces

}



// Settings for the layer addition.
addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName
{
relativeSizes false; // was true
layers
{

Innenteil
{nSurfaceLayers 3;} // 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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