[martinmat13]

I tried to make a domain for my simulation for a 2d case. But when I import my stl file and execute snappyHexMesh, the stl file is split up into 4 cells in z-direction and the base mesh is 1 cell (which is desired as for a 2d case).

How can I resolve this issue with the stl file.

The images and snappyHexMeshDict are shown here below.

************************************************** *************

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v2212 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location system;
object snappyHexMeshDict;
}
//************************************************** ******************//

castellatedMesh true;
snap true;
addLayers false;
geometry
{
fish.stl { type triSurfaceMesh; name fish; }
refinementeBox
{
type searchableBox;
min (0.9 0 0);
max (2.4 0.75 0.01);
}

fishRefinementBox
{
type searchableBox;
min (1.38 0.33 0);
max (1.72 0.42 0.01);
}

}

castellatedMeshControls
{
features
(
{ file "fish.eMesh";
level 2 ;
//refineFeatureEdgesOnly false;
}
);

refinementSurfaces
{
fish {
level (2 2);
patchInfo
{
type wall;
}
}


}

refinementRegions
{
/*fish
{

mode outside;
levels ((0.01 1));


}*/

/*refinementeBox
{

mode inside;
levels ((1 1));

}*/

fishRefinementBox
{

mode inside;
levels ((1 1));

}

}

locationInMesh (1.2 0.54 0.0009); //(0.2 0.2 0.1);
maxLocalCells 100000;
maxGlobalCells 200000;
minRefinementCells 0;
nCellsBetweenLevels 1;
resolveFeatureAngle 20;
allowFreeStandingZoneFaces true;
planarAngle 30.0;
maxLoadUnbalance 0.1;
}

snapControls
{
nSolveIter 300;
nSmoothPatch 5;
tolerance 2.0;
nRelaxIter 25;
nFeatureSnapIter 20;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap true;
}

addLayersControls
{
layers
{
//"patch_inlet-fancoil.*"
//{
//nSurfaceLayers 10;
//}
}

relativeSizes true;
expansionRatio 1.05;
finalLayerThickness 0.5;
minThickness 0.05;
nGrow 0;
featureAngle 130;
slipFeatureAngle 60;
nRelaxIter 5;
nSmoothSurfaceNormals 1;
nSmoothNormals 3;
nSmoothThickness 10;
maxFaceThicknessRatio 0.5;
maxThicknessToMedialRatio 0.3;
minMedialAxisAngle 90;
nBufferCellsNoExtrude 0;
nLayerIter 50;
nRelaxedIter 20;
writeVTK false;
noErrors false;
layerRecovery 1;
growZoneLayers false;
projectGrownUp 0.0;
}

meshQualityControls
{
maxNonOrtho 65.0;
maxBoundarySkewness 3;
maxInternalSkewness 3;
maxConcave 65.0;
minFlatness 0.5;
minVol 1.0E-13;
minTetQuality 1.0E-15;
minArea -1.0;
minTwist 0.02;
minDeterminant 0.001;
minFaceWeight 0.05;
minVolRatio 0.01;
minTriangleTwist -1.0;
nSmoothScale 4;
errorReduction 0.75;
relaxed
{
maxNonOrtho 65;
}
}

debug 0;
mergeTolerance 1.0E-2;
autoBlockMesh true;

[Yann]

Hello Martin,

Due to the way snappy refines the mesh (octree structure), it cannot mesh 2D cases out of the box since it also refines the 3rd dimension.
However, you can mesh your geometry in snappy as you already did, then use the extrudeMesh utility to extrude one of the face of your mesh and get the proper one-cell thickness mesh you need for your 2D case.

I didn't search for it but you should be able to find examples in the tutorials or on the forum.

Regards,
Yann

[GerhardHolzinger]

Extrude a one-cell layer of the front or back patch and throw away the original mesh.

[martinmat13]

Originally Posted by Yann

Hello Martin,

Due to the way snappy refines the mesh (octree structure), it cannot mesh 2D cases out of the box since it also refines the 3rd dimension.
However, you can mesh your geometry in snappy as you already did, then use the extrudeMesh utility to extrude one of the face of your mesh and get the proper one-cell thickness mesh you need for your 2D case.

I didn't search for it but you should be able to find examples in the tutorials or on the forum.

Regards,
Yann

Dear Mr. Yann

Thank you for your reply and suggestion. Good news is, it worked the way you suggested and I was able to extrude my mesh. Much thanks and regards.

Martin