[BakedAlmonds]

Hi,

I am learning to add layers so as to improve y+ for the use of wall functions. I am using the windaroundbuildings file in the OF tutorials as a base case.
I followed this thread closely: http://www.cfd-online.com/Forums/ope...defined-2.html

I used both the feature and split angle speficied. But explicit feature snap was used instead in this case.

Originally Posted by LVDH

featureAngle 330;
slipFeatureAngle 330;

After generating sHM, the layers generated was not uniform, it is good in some areas and bad in some. I have attached a picture to show the good (circled in green) and bad (circled in red).

Can anyone explain why does this happen?
Also, what is the slipFeatureAngle used for?

[BakedAlmonds]

this is the sHMD used:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#includeEtc "caseDicts/mesh/generation/snappyHexMeshDict.cfg"

castellatedMesh true;
snap            true;
addLayers       true;

geometry
{
    buildings.obj
    {
        type triSurfaceMesh;
        name buildings;
    }

    refinementBox
    {
        type searchableBox;
        min  (  0   0   0);
        max  (250 180  90);
    }
};

castellatedMeshControls
{
    features
    (
      { file  "buildings.eMesh"; level 1; }
    );

    refinementSurfaces
    {
        buildings
        {
            level (3 3);
            patchInfo { type wall; }
        }
    }

    refinementRegions
    {
        refinementBox
        {
            mode inside;
            levels ((1E15 2));
        }
    }

    locationInMesh (1 1 1);
}

snapControls
{
    explicitFeatureSnap    true;
    implicitFeatureSnap    false;
}

addLayersControls
{
    layers
    {
        "buildings.*"
        {
            nSurfaceLayers 8;
        }
    }

    relativeSizes       false;
    expansionRatio      1.1;

    // Wanted thickness of final added cell layer. If multiple layers
    // is the
    // thickness of the layer furthest away from the wall.
    // Relative to undistorted size of cell outside layer.
    // is the thickness of the layer furthest away from the wall.
    // See relativeSizes parameter.
    // firstLayerThickness 0.05; can use first as well
    finalLayerThickness 0.3;

    // Minimum thickness of cell layer. If for any reason layer
    // cannot be above minThickness do not add layer.
    // Relative to undistorted size of cell outside layer.
    minThickness        0;
    nGrow 0; // was 1 


    // Advanced settings

    featureAngle 330; // was 70 //- When not to extrude surface. 0 is flat, 90 is right angle.
    // At non-patched sides allow mesh to slip if extrusion direction makes
    // angle larger than slipFeatureAngle.
    slipFeatureAngle 5;//fix

    nRelaxIter 3;  //- Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh.
    nSmoothSurfaceNormals 1;  // Number of smoothing iterations of surface normals
    nSmoothNormals 3; // 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 50; // Overall max number of layer addition iterations

}

meshQualityControls
{
}

writeFlags
(
    scalarLevels
    layerSets
    layerFields
);

mergeTolerance 1e-6;

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