[tale_aasland]

Hi,


I'm new with openFoam, and trying to learn snappyhexmesh. Right now, I'm working on a mesh for the bottom of a pontoon, but strange abberations show up when I run snappyhexmesh. These are mostly outside of the refined regions, as shown in the screenshot (I've included a screenshot of the 3D geometry, for reference).


Clearly, I'm doing something wrong in the setup, though I can't figure out what. Any help is much appreciated.



Here's the dict:


/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 12
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //


castellatedMesh true;
snap true;
addLayers false;

geometry //stl file, OpenFoam bounding geometry or both
{
pontoon
{
type triSurfaceMesh;
file "pontoon.stl";
}

bigbox
{
type searchableBox;
min (-30 -15 0);
max (40 15 10);
}
box
{
type searchableBox;
min (-27 -9 0);
max (30 9 6);
}

};

castellatedMeshControls
{
maxLocalCells 500000;
maxGlobalCells 5000000;
minRefinementCells 0;
nCellsBetweenLevels 1;

features
(
{
file "pontoon.eMesh";
level 3;
}
);


refinementSurfaces
{
pontoon
{
// Surface-wise min and max refinement level
level (4 4);
}

}


refinementRegions
{
box
{
mode inside;
level 2;
}
bigbox
{
mode inside;
level 1;
}
}

resolveFeatureAngle 30;
planarAngle 30;



allowFreeStandingZoneFaces true;
insidePoint (-30 -20 5);
};


snapControls
{
nSmoothPatch 3;
tolerance 1;
nSolveIter 100;
nRelaxIter 5;

// Feature snapping
nFeatureSnapIter 10;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap true;
};



meshQualityControls
{
maxNonOrtho 75;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;

minVol 1.00E-13;
minTetQuality 1e15;

minArea -1;
minTwist 0.02;
minDeterminant 0.001;
minFaceWeight 0.05;
minVolRatio 0.01;
minTriangleTwist -1;
minFlatness 0.5;
nSmoothScale 4;

errorReduction 0.75;
};

mergeTolerance 1e-6;

[AtoHM]

Its just a visualization issue. Per default, paraview decomposes the hexahedrons into tetraeder cells. You can see here how to get a representation of the hexahedrons: How to visualize polyhedron mesh in paraview


Furthermore, if you create a slice or clip of the mesh, it can happen that cell layers are cut at weird positions. This leads to the lines you see. You can avoid this in the display options of the filter in the properties, look for a checkbox option saying "crinkle". do Squiggles in snappyHexMesh effect quality