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Heroic December 18, 2012 10:52

Low determinant in OpenFOAM

Lately I seem to be having problems with the determinant of my cells. Right now I am working on a tetra-only mesh, which I then export for Fluent v6 and then convert into OpenFOAM format.

According to Ansys ICEM, the quality of my mesh is sufficient (At least 0.15 on the quality criterium), however when I do a checkMesh -allTopology -allGeometry I get a failed mesh check due to a high number of low determinant cells.

Returning to Ansys and checking for the determinant criterion, I get just 1 bar for max quality determinants, which obviously is not the case...

When checking for Quality:
Min = 0.190245, max = 0.999119, mean = 0.693216455497
673866 elements with the "Quality" diagnostic

When checking for Determinant:
Min = 1, max = 1, mean = 1.0
603610 elements with the "Determinant" diagnostic
70256 elements for which this diagnostic is undefined

Am I doing something wrong? Is this a bug? Or does it have to do with the conversion from Fluent mesh to OpenFOAM?

Advice is really appreciated, as I obviously cannot improve my meshes if I do not know what is wrong :)

Kind regards.


Checking geometry...
    Overall domain bounding box (-6.53535 -0.38 -6.45979e-05) (16 8.07706 7.933)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (7.23755e-17 -2.26157e-17 3.46756e-16) OK.
    Max cell openness = 2.8738e-16 OK.
    Max aspect ratio = 5.88042 OK.
    Minumum face area = 2.70686e-07. Maximum face area = 0.712406.  Face area magnitudes OK.
    Min volume = 1.84351e-10. Max volume = 0.196281.  Total volume = 1279.31.  Cell volumes OK.
    Mesh non-orthogonality Max: 69.3797 average: 18.8835
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.699921 OK.
    Coupled point location match (average 0) OK.
    Face tets OK.
    Min/max edge length = 0.000426632 1.54807 OK.
    All angles in faces OK.
    All face flatness OK.
    Cell determinant (wellposedness) : minimum: 0 average: 1.41126
 ***Cells with small determinant found, number of cells: 2249
  <<Writing 2249 under-determined cells to set underdeterminedCells
    Concave cell check OK.

Failed 1 mesh checks.

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