[TheMadHungarian]

Hi all, a longtime "lurker" here. I have learnt a lot from this community but there is one case now I need some special hints.


I'm using blockMeshDict to create a spherical mesh with a spherical void in the middle (a spherical shell in essence). The meshing goes great but when checking the inside of the mesh with Paraview and "Slice" or "Clip", I see several ill-formed cells. How do I fix those? I figured the mesher would be smart enough to create a bunch of slightly spherical "bricks" some some cells are wedge-shaped...I guess. I'm still getting good results from sonicFoam but these artifacts bother me.


The simulation I'm running is a transonic blast expansion, FYI. We're trying to determine the shock wave travel characteristics.


blockMesh runs without errors, checkMesh also "OK" everything, and I also ran renumberMesh...all good. Still getting those weird artifacts. What's the deal?????



So, I need inputs, comments, hints, etc.


Thanks!!!!!


Pictures attached are of the actual mesh in question.

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

verbose yes;

geometry {
    sphere1 {
        type searchableSphere;
        centre (0 0 0);
        radius 3.5;
    }
    sphere2 {
        type searchableSphere;
        centre (0 0 0);
        radius 50;
    }
}

scale 1;

n1 20;

v    28.8675;//0.5773502;
mv  -28.8675; //-0.5773502;
vh   2.0207; //0.2886751;
mvh -2.0207; //-0.2886751;

a    35.3553; //0.7071067;
ma  -35.3553; //-0.7071067;
ah   2.47487; //0.3464101;
mah -2.47487; //-0.3464101;

vertices (
    ($mvh $mvh $mvh)
    ( $vh $mvh $mvh)
    ( $vh  $vh $mvh)
    ($mvh  $vh $mvh)
    ($mvh $mvh  $vh)
    ( $vh $mvh  $vh)
    ( $vh  $vh  $vh)
    ($mvh  $vh  $vh) //7

    ($mv $mv $mv) //8
    ( $v $mv $mv)
    ( $v  $v $mv)
    ($mv  $v $mv)
    ($mv $mv  $v)
    ( $v $mv  $v)
    ( $v  $v  $v)
    ($mv  $v  $v) //15
);

blocks (
    hex ( 9  8 12 13  1  0  4  5) ($n1 $n1 $n1) simpleGrading (1 1 1)
    hex (10  9 13 14  2  1  5  6) ($n1 $n1 $n1) simpleGrading (1 1 1)
    hex (11 10 14 15  3  2  6  7) ($n1 $n1 $n1) simpleGrading (1 1 1)
    hex ( 8 11 15 12  0  3  7  4) ($n1 $n1 $n1) simpleGrading (1 1 1)
    hex ( 8  9 10 11  0  1  2  3) ($n1 $n1 $n1) simpleGrading (1 1 1)
    hex (13 12 15 14  5  4  7  6) ($n1 $n1 $n1) simpleGrading (1 1 1)
);

edges (
    arc  8  9 (0 $ma $ma)
    arc 10 11 (0 $a $ma)
    arc 14 15 (0 $a $a)
    arc 12 13 (0 $ma $a)

    arc  8 11 ($ma 0 $ma)
    arc  9 10 ($a 0 $ma)
    arc 13 14 ($a 0 $a)
    arc 12 15 ($ma 0 $a)

    arc  8 12 ($ma $ma 0)
    arc  9 13 ($a $ma 0)
    arc 10 14 ($a $a 0)
    arc 11 15 ($ma $a 0)


    arc  0  1 (0 $mah $mah)
    arc  2  3 (0 $ah $mah)
    arc  6  7 (0 $ah $ah)
    arc  4  5 (0 $mah $ah)

    arc  0  3 ($mah 0 $mah)
    arc  1  2 ($ah 0 $mah)
    arc  5  6 ($ah 0 $ah)
    arc  4  7 ($mah 0 $ah)

    arc  0  4 ($mah $mah 0)
    arc  1  5 ($ah $mah 0)
    arc  2  6 ($ah $ah 0)
    arc  3  7 ($mah $ah 0)
);

faces (
    project ( 0 4 7 3) sphere1
    project (2 6 5 1) sphere1
    project ( 1 5 4  0) sphere1
    project (3 7 6 2) sphere1
    project ( 0 3 2 1) sphere1
    project (4 5 6 7) sphere1

    project (8 12 15 11) sphere2
    project (10 14 13 9) sphere2
    project (9 13 12 8) sphere2
    project (11 15 14 10) sphere2
    project (8 11 10 9) sphere2
    project (12 13 14 15) sphere2
);

boundary (
    atmosphere {
        type patch;
        faces
        (
            ( 8 12 15 11)
            (10 14 13  9)
            ( 9 13 12  8)
            (11 15 14 10)
            ( 8 11 10  9)
            (12 13 14 15)
        );
    }
    blast {
        type patch;
        faces
        (
            ( 0 4 7 3)
            (2 6 5 1)
            (1 5 4 0)
            (3 7 6 2)
            (0 3 2 1)
            (4 5 6 7)
        );
    }
);

checkMesh results show no issues:

Mesh stats
    points:           393682
    faces:            1161600
    internal faces:   1142400
    cells:            384000
    faces per cell:   6
    boundary patches: 2
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     384000
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology
    atmosphere          9600     9602     ok (closed singly connected)
    blast               9600     9602     ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-50 -50 -50) (50 50 50)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (2.65525e-016 2.44712e-016 2.10464e-016) OK.
    Max cell openness = 3.83177e-016 OK.
    Max aspect ratio = 5.79932 OK.
    Minimum face area = 0.0104915. Maximum face area = 4.08288.  Face area magnitudes OK.
    Min volume = 0.018498. Max volume = 4.59341.  Total volume = 522007.  Cell volumes OK.
    Mesh non-orthogonality Max: 50.2352 average: 8.22207
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.470245 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

[TheMadHungarian]

I moved this thread to the "blockMesh" subsection...Mod, can you please close this one? Thanks!