SnappyHexMesh Not Refining Cells
 

Hi All,


I'm running into issues trying to get my mesh to refine near the surface. I have run SHM many times, and been able to get different levels of surface refinement across a variety of surfaces, but in this case I simply can't get any level of refinement, the cells are all the same size in the domain. SHM runs without any errors, and the STL snaps into the domain no problem.



My blockMesh and SHM files are listed below, and a screenshot of what the domain looks like after Meshing is attached:


BlockMesh


convertToMeters 1;

vertices
(
(44 -2451510 -1765)
(1465 -2451510 -1765)
(1465 -2449783 -1765)
(44 -2449783 -1765)
(44 -2451510 -1400)
(1465 -2451510 -1400)
(1465 -2449783 -1400)
(44 -2449783 -1400)
);

blocks
(
hex (0 1 2 3 4 5 6 7) (5 6 1) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
outlet
{
type patch;
faces
(
(0 4 7 3)
(3 7 6 2)

);
}

inlet
{
type patch;
faces
(
(2 6 5 1)
(1 5 4 0)
);
}

Mesa
{
type wall;
faces
(
(0 3 2 1)
);
}
top
{
type patch;
faces
(
(4 5 6 7)
);
}
);

mergePatchPairs
(
);


snappyHexMesh



/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 7
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
castellatedMesh true;
snap true;
addLayers true;

geometry
{
refinementBox
{
type searchableBox;
min (0 -2451600 -2000);
max (1470 -2440000 -1000);
}

Mesa
{
type triSurfaceMesh;
file "Mesa.stl";
}
};


castellatedMeshControls
{
maxLocalCells 2000000000;

maxGlobalCells 2000000000;

minRefinementCells 1;

maxLoadUnbalance 0.10;

nCellsBetweenLevels 1;

features
(

);

refinementSurfaces
{
Mesa
{
level (0 2);

regions
{
refinementBox
{
level (3 3);
}
}
}
}

resolveFeatureAngle 5;

refinementRegions
{

refinementBox
{
mode inside;
levels ((5 5));
}

}

locationInMesh (1000 -2450000 -1600);

allowFreeStandingZoneFaces true;
}

snapControls
{
nSmoothPatch 3;

tolerance 1.0; //was 2.0

nSolveIter 30;

nRelaxIter 5;
}


addLayersControls
{
relativeSizes true;

layers
{

}

expansionRatio 1.0;

finalLayerThickness 1; //was 0.3

minThickness 0.25;

nGrow 0;

featureAngle 60;

nRelaxIter 5;

nSmoothSurfaceNormals 1;

nSmoothNormals 3;

nSmoothThickness 10;

maxFaceThicknessRatio 0.5;

maxThicknessToMedialRatio 0.3;

minMedianAxisAngle 90;

nBufferCellsNoExtrude 0;

nLayerIter 50;

nRelaxedIter 20;
}

meshQualityControls
{
maxNonOrtho 45;
maxBoundarySkewness 10;
maxInternalSkewness 2;

maxConcave 80;

minVol 1e-13;

minTetQuality 1e-30;

minArea -1;

minTwist 0.05;

minDeterminant 0.001;

minFaceWeight 0.05;

minVolRatio 0.01;

minTriangleTwist -1;

nSmoothScale 4;

errorReduction 0.75;

relaxed
{
maxNonOrtho 45;
}
}

mergeTolerance 1e-5;


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



Using this SHM script on other domains (switching relevant values out) has produced refinement before, but not in this case. If anyone could provide some insight that would be greatly appreciated

This looks like an error to me. Do you write out a log file for your sHM-Runs? If you do, it should show an error. The refinementBox is not a region of Mesa, it should be a separate entry.

Another hint: set the locationInMesh components to some odd values to avoid it landing on a node -> this can cause issues.

Hi Ato,

Thanks for the reply, I don't write out a log after it's finished I just watch it as it does it. It finishes with no errors and checkMesh produces no errors either.

What do you mean regarding the refinement box? Apologies for the confusion

CheckMesh wouldn't show errors, as you have the blockMesh it can work on.

I am not sure why you mention the refinementBox at all in refinementSurfaces subdictionary, but if you do, it should probably look like this


But normally, you would just have it in refinementRegions (as you have already). There it gets refined to lvl 5, no need to add another refinement here. Although this seems not to be the real cause of your issue. Try using an odd location in mesh like locationInMesh (999.214 -2450001.214 -1600.145);
Hopefully this helps.