[steddy]

Hi all,
I am trying to make an accurate mesh of an Ahmed body.

This is what the Castellated mesh looks like: https://imgur.com/a/pyZWWaj
All the cells have a nice cubic shape.

This is what the mesh looks like after Snap: https://imgur.com/a/WEn1XwI
You can see that the cells in direct contact with the body's surface have now a "rectangular" shape; wereas in the castellated mesh they were cubes.

In my opinion, this could be an issue in the subsequent phase of layer addition, because the transition from the region to the final layer is disturbed by this weird region, whose cells have a rectangular shape instead of a cubic one.

Are my concerns valid? Could this "error" impair the final result? Can this error be avoided and solved by tuning the mesh quality controls? I am using the default ones: https://pastebin.com/4C0a4yZB

Thank you in advance.
A
This is the relevant content of the snappyHexMeshDict.

geometry
{
    ahmed
    {
        type triSurfaceMesh;
        // file "ahmed.obj";
        file "ahmed.stl";
    }

    refinementBoxEight
    {
        type searchableBox;
	min (-0.2 -0.25 0.0);
        max (1.1 0.25 0.4);
    }

    refinementBoxSix
    {
        type searchableBox;
        min (-2.0 -0.35 0.0);
        max ( 4.0  0.35 0.5);
    }

    refinementBoxFour
    {
        type searchableBox;
        min (-5.0 -1 0.0);
        max ( 15.0 1.00 0.5);
    }
};

castellatedMeshControls
{
    maxLocalCells 10000000;

    maxGlobalCells 200000000;

    minRefinementCells 10;

    maxLoadUnbalance 0.10;


    nCellsBetweenLevels 4;

    features
    (
	
        {
            file "ahmed.eMesh";
            level 8;
        }
	
    );
    
    refinementSurfaces
    {
        ahmed
        {
            level (8 8);

            patchInfo
            {
                type wall;
                inGroups (ahmedGroup);
            }
        }
    }

    resolveFeatureAngle 15;

    refinementRegions
    {
        refinementBoxSix
        {
            mode inside;
	    levels ((1E15 6));
        }

        refinementBoxFour
        {
            mode inside;
	    levels ((1E15 4));
        }

        refinementBoxEight
        {
            mode inside;
	    levels ((1E15 8));
	}
    }
    locationInMesh (3.0001 3.0001 0.43);

    allowFreeStandingZoneFaces true;
}

[steddy]

I forgot to add that this effect is more or less evident depending by the mesh. In some of my other meshes, it is much more visible: The cells in contact with the body's surface are very long and thin rectangles.