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[snappyHexMesh] Problem with SnappyHexMesh

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Old   March 20, 2017, 11:01
Default Problem with SnappyHexMesh
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Joe-Hin Yip
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Hi Foamers, i got a problem to do a mesh without to delete my Inlet and Outlet..

after the command to mesh with SHM, ge gonna delete all my "zero-sized-patches", which is my outlet, inlet and other walls


Thanks everyone for help !


This is the log and down below the dict from Snappy

patch faces layers overall thickness
[m] [%]
----- ----- ------ --- ---
ein 5121 2.63 0.000316 83.6
aus 0 0 0 0
kammer 628 2.77 0.000329 87
diff 0 0 0 0


Removing zero-sized patches:
maxY type patch at position 0
minX type patch at position 1
maxX type patch at position 2
minY type patch at position 3
minZ type patch at position 4
maxZ type patch at position 5
inlet type wall at position 6
aus type wall at position 9
diff type wall at position 11

Layer mesh : cells:24817 faces:79720 points:30432

SnappyHexmeshDict

/*--------------------------------*- 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 true; // decide to add viscous layers ?


geometry // Load in STL files here
{
inlet.stl {type triSurfaceMesh; name inlet;}
outlet.stl {type triSurfaceMesh; name outlet;}
ein.stl {type triSurfaceMesh; name ein;}
aus.stl {type triSurfaceMesh; name aus;}
kammer.stl {type triSurfaceMesh; name kammer;}
diff.stl {type triSurfaceMesh; name diff;}
ding.stl {type triSurfaceMesh; name ding;}
refinementBox {type searchableBox; min (-0.1 -0.1 -0.05); max ( 0.1 0.1 0.05);}
};

castellatedMeshControls
{
maxLocalCells 1000000; //max cells per CPU core
maxGlobalCells 2000000; //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 "inlet.eMesh"; level 3;}
{file "outlet.eMesh"; level 3;}
{file "ein.eMesh"; level 3;}
{file "aus.eMesh"; level 3;}
{file "kammer.eMesh"; level 3;}
{file "diff.eMesh"; level 3;}
);

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

refinementSurfaces // Surface-wise min and max refinement level
{
inlet {level (0 0);}
outlet {level (0 0);}
ein {level (3 3);}
aus {level (5 5);} // was 4 4
kammer{level (5 5);} // was 4 4
diff{level (5 5);} // was 4 4
}


resolveFeatureAngle 80; // Resolve sharp angles // Default 30
refinementRegions // In descending levels of fine-ness
{volume {mode distance; levels ((0.0006 4) (0.002 3) (0.01 2));}} // was ((0.001 4) (0.003 3) (0.01 2))
locationInMesh (0 0 0); //to decide which side of mesh to keep **
allowFreeStandingZoneFaces true;
}


// 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.
addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName
{
relativeSizes false; // was true
layers
{
ein
{nSurfaceLayers 3;} // was 3
aus
{nSurfaceLayers 3;} // was 3
kammer
{nSurfaceLayers 3;} // was 3
diff
{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;


// ************************************************** *********************** //

Last edited by Joehin; March 21, 2017 at 04:39. Reason: wrong
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Old   March 27, 2017, 10:48
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Weird... see if the size of those patches are not too small even with refinement.
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Old   March 27, 2017, 11:21
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Joe-Hin Yip
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i solved my problem, my blockMesh was to small

Thank your anyway for help
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