[Kim sung hwan]

Dear cfd-users,

i have tried making external mesh by running snappyHexMesh for simulating a OneraM6 wing. but i meet a problem the addlayer processing in snappyHexMesh. Until snapping, i got reasonable snapping results on the wing surface.

however, after addlayer step, i found some bumps between upper and lower level of refinement level. when i got uniform cells near a surface using distance refinement, i could
resolve this problem. but it makes too many total cells so, it's not efficient.

I have tried many parametric study, but i can't find the solution about this issue.


I attached four screenshots and below there's my snappyHexMeshDict.

I would appreciate any help for solve this problem.

/*--------------------------------*- C++ -*----------------------------------*\
|       o          |                                                          |
|    o     o       | HelyxOS                                                  |
|   o   O   o      | Version: v1.0.3                                           |
|    o     o       | Web:     http://www.engys.com                            |
|       o          |                                                          |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object snappyHexMeshDict;
}

    castellatedMesh true;
    snap true;
    addLayers true;
    geometry
    {
        M6.stl
        {
            type triSurfaceMesh;
            name M6;
        }

        box1
        {
            type searchableBox;
            min (-0.5 0.0 -0.5 );
            max (2.0 1.5 0.5 );
        }

    }

    castellatedMeshControls
    {
        features
        (
        
        {
            file "M6.eMesh";
            level 8;
        }

        );
        refinementSurfaces
        {
            M6
            {
                regions
                {
                }

                level (7 8 );
            }

        }

        refinementRegions
        {
            box1
            {
                mode inside;
                levels (( 1E5 3 ));
            }

        }

        locationInMesh (3.0 3.0 1.0 );
        maxLocalCells 1000000;
        maxGlobalCells 2000000;
        minRefinementCells 0;
        nCellsBetweenLevels 5;
        resolveFeatureAngle 5;
        allowFreeStandingZoneFaces false;
    }

    snapControls
    {
        nSolveIter 300;
        nSmoothPatch 3;
        tolerance 1.0;
        nRelaxIter 5;
        nFeatureSnapIter 10;
        implicitFeatureSnap false;
        explicitFeatureSnap true;
        multiRegionFeatureSnap false;
    }

    addLayersControls
    {
        layers
        {
            M6_ascii_io_exported_from_Pointwise
            {
                nSurfaceLayers 2;
            }

        }

        relativeSizes false;
        expansionRatio 1.1;
        finalLayerThickness 2.0E-4;
        minThickness 1.0E-5;
        nGrow 0;
        featureAngle 60;
        slipFeatureAngle 30;
        nRelaxIter 3;
        nSmoothSurfaceNormals 1;
        nSmoothNormals 3;
        nSmoothThickness 10;
        maxFaceThicknessRatio 0.8;
        maxThicknessToMedialRatio 0.3;
        minMedianAxisAngle 90;
        nBufferCellsNoExtrude 0;
        nLayerIter 50;
        nRelaxedIter 20;
    }

    meshQualityControls
    {
        maxNonOrtho 65;
        maxBoundarySkewness 20;
        maxInternalSkewness 4;
        maxConcave 80;
        minFlatness 0.5;
        minVol 1.00E-13;
        minTetQuality -1e30;
        minArea -1;
        minTwist 0.02;
        minDeterminant 0.001;
        minFaceWeight 0.02;
        minVolRatio 0.01;
        minTriangleTwist -1;
        nSmoothScale 4;
        errorReduction 0.75;
    }

    debug 0;
    mergeTolerance 1E-6;