[charles1]

I start with a rectangular block mesh and have a stl file that defines a boundary between solid and fluid within that rectangular region.

My snappyHexMeshDict is:

castellatedMesh true;
snap            true;
addLayers       true;

geometry
{
    solid_to_fluid
    {
        type triSurfaceMesh;
        file "solid_to_fluid.stl";
    }
};

castellatedMeshControls
{
    refinementSurfaces
    {

        solid_to_fluid
        {
            level (3 4);
            faceZone solid_to_fluid;
            cellZone solid;
            cellZoneInside insidePoint;
            insidePoint (0.0 0.0 0.0);
        }

    }

    nCellsBetweenLevels 1;

    refinementRegions
    {}

    locationInMesh (-0.019 0.0 0.0);
}

snapControls
{
        nSmoothPatch 3;
}

addLayersControls
{
    relativeSizes       true;
    minThickness        1;
    finalLayerThickness 1;
    expansionRatio      1;
    layers
    {}
}

meshQualityControls
{
        maxNonOrtho     65;
}

and I get the following output at the end of the snappyHexMesh command:

Checking faces in error :
    non-orthogonality > 65  degrees                        : 13930
    faces with face pyramid volume < 1e-13                 : 1585834
    faces with concavity > 80  degrees                     : 0
    faces with skewness > 4   (internal) or 20  (boundary) : 0
    faces with interpolation weights (0..1)  < 0.05        : 0
    faces with volume ratio of neighbour cells < 0.01      : 0
    faces with face twist < 0.02                           : 0
    faces on cells with determinant < 0.001                : 0
Finished meshing with 1599764 illegal faces (concave, zero area or negative cell pyramid volume)

This sounds like an indication of poor quality cells, is that correct? When I open the mesh in paraview, it looks OK, so I'm not sure where these bad faces are.

When I try to run the solution (conjugate heat transfer), the solver stops saying that it encountered a negative temperature. So the solution seems to be diverging and I'm wondering if its because of a bad mesh.

I appreciate your help!

[farzadmech]

Dear Charles
did you find what is illegal faces means? I also have illegal faces after I do SHM but when I check the mesh using checkMesh everything seems fine. I have attached the figure to the post.


Thanks,
Farzad

Originally Posted by charles1

I start with a rectangular block mesh and have a stl file that defines a boundary between solid and fluid within that rectangular region.

My snappyHexMeshDict is:

castellatedMesh true;
snap            true;
addLayers       true;

geometry
{
    solid_to_fluid
    {
        type triSurfaceMesh;
        file "solid_to_fluid.stl";
    }
};

castellatedMeshControls
{
    refinementSurfaces
    {

        solid_to_fluid
        {
            level (3 4);
            faceZone solid_to_fluid;
            cellZone solid;
            cellZoneInside insidePoint;
            insidePoint (0.0 0.0 0.0);
        }

    }

    nCellsBetweenLevels 1;

    refinementRegions
    {}

    locationInMesh (-0.019 0.0 0.0);
}

snapControls
{
        nSmoothPatch 3;
}

addLayersControls
{
    relativeSizes       true;
    minThickness        1;
    finalLayerThickness 1;
    expansionRatio      1;
    layers
    {}
}

meshQualityControls
{
        maxNonOrtho     65;
}

and I get the following output at the end of the snappyHexMesh command:

Checking faces in error :
    non-orthogonality > 65  degrees                        : 13930
    faces with face pyramid volume < 1e-13                 : 1585834
    faces with concavity > 80  degrees                     : 0
    faces with skewness > 4   (internal) or 20  (boundary) : 0
    faces with interpolation weights (0..1)  < 0.05        : 0
    faces with volume ratio of neighbour cells < 0.01      : 0
    faces with face twist < 0.02                           : 0
    faces on cells with determinant < 0.001                : 0
Finished meshing with 1599764 illegal faces (concave, zero area or negative cell pyramid volume)

This sounds like an indication of poor quality cells, is that correct? When I open the mesh in paraview, it looks OK, so I'm not sure where these bad faces are.

When I try to run the solution (conjugate heat transfer), the solver stops saying that it encountered a negative temperature. So the solution seems to be diverging and I'm wondering if its because of a bad mesh.

I appreciate your help!