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Old   October 8, 2016, 12:09
Default SnappyHexMesh Patch Problem
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Hey everbody,

I`struggleing with snappyhexmesh. There must be a problem with the patches, however I have no idea where. I created my stl-files by exporting groups from salome.

Attched you can see the checkMesh-reply and the sHMD.
I would appreciate if someone could give me advise.

Great regards



On the one hand I get /*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 4.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 4.0-665f1db4c1f1
Exec : checkMesh
Date : Oct 08 2016
Time : 18:05:34
Host : "albrecht-cae-CELSIUS-M720"
PID : 6446
Case : /home/albrecht_cae/Schreibtisch/OpenFoam/20160924_valve
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 618285
faces: 1700663
internal faces: 1595529
cells: 541479
faces per cell: 6.0873866
boundary patches: 3
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 500090
prisms: 20856
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 20533
Breakdown of polyhedra by number of faces:
faces number of cells
5 622
6 3305
9 11371
12 4209
15 961
18 65

Checking topology...
****Problem with boundary patch 0 named inlet of type wall. The patch should start on face no 1595529 and the patch specifies 1595531.
Possibly consecutive patches have this same problem. Suppressing future warnings.
***Boundary definition is in error.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
inlet 894 990 ok (non-closed singly connected)
outlet 820 899 ok (non-closed singly connected)
patchwall 103418 103722 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.0099956077 -0.032523782 -0.0099985384) (0.02 0.002504085 0.0099985384)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-6.785461e-16 4.0906973e-15 3.3559227e-15) OK.
Max cell openness = 4.1354321e-16 OK.
Max aspect ratio = 5.7326472 OK.
Minimum face area = 2.773767e-09. Maximum face area = 4.6502648e-07. Face area magnitudes OK.
Min volume = 8.4842851e-13. Max volume = 1.9190422e-10. Total volume = 2.5154271e-06. Cell volumes OK.
Mesh non-orthogonality Max: 51.877025 average: 7.5311999
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.6908976 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End


And the sHMD:

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
{
inlet.stl {type triSurfaceMesh; name inlet;}
outlet.stl {type triSurfaceMesh; name outlet;}
patchwall.stl {type triSurfaceMesh; name patchwall;}
completegeometry.stl {type triSurfaceMesh; name completegeometry;}
};

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 0.1;
nCellsBetweenLevels 7; // 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 0;}
{file "outlet.eMesh"; level 0;}
{file "patchwall.eMesh"; level 0;}
);

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

refinementSurfaces // Surface-wise min and max refinement level
{
inlet {level (0 0);}
outlet {level (0 0);}
patchwall {level (2 2);}
}


resolveFeatureAngle 10; // Resolve sharp angles // Default 30
refinementRegions // In descending levels of fine-ness
{completegeometry {mode distance; levels ((0.0002 1) (0.0005 1) (0.01 0));}} // was ((0.001 4) (0.003 3) (0.01 2))
locationInMesh (0 0 -0.007); //to decide which side of mesh to keep **
allowFreeStandingZoneFaces true;
}


// Settings for the snapping.
snapControls
{
nSmoothPatch 0;
tolerance 4.0;
nSolveIter 300; //30
nRelaxIter 10; //5
nFeatureSnapIter 20; // 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 true; // was true
layers
{
patchwall
{
nSurfaceLayers 3;
} // was 3
}

expansionRatio 1.2;
finalLayerThickness 0.5; //was 0.00016
minThickness 0.2; //was 0.00008
nGrow 0; // was 1


// Advanced settings

featureAngle 180; // was 70 //- When not to extrude surface. 0 is flat, 90 is right angle.
nRelaxIter 10; //- Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh.
nSmoothSurfaceNormals 5; // Number of smoothing iterations of surface normals
nSmoothNormals 8; // 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 100; // 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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