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[blockMesh] Non-orthogonal cells checkMesh

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Old   October 23, 2019, 12:18
Default Non-orthogonal cells checkMesh
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Nat K
Join Date: Oct 2017
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Hi,

I am simulating the flow within a cone-plate rheometer (see attached image for geometry). The red region is the fluid which I am simulating and is being meshed using blockMesh. I tried to create the mesh in blocks using an O-grid method.

I am able to mesh the geometry, however, I tend to get a large mesh non-orthogonality value (89) and there are several non-orthogonal faces when I use checkMesh (see below). I have viewed the areas where this occurs I can see these occur at the truncated region as it is a very small region compared to the size of the domain. How can I reduce the non-orthogonality in this region?

checkMesh log

Code:
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           10220451
    faces:            30220000
    internal faces:   29780000
    cells:            10000000
    faces per cell:   6
    boundary patches: 3
    point zones:      0
    face zones:       0
    cell zones:       2

Overall number of cells of each type:
    hexahedra:     10000000
    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
    airInterface        40000    40800    ok (non-closed singly connected)
    plate               200000   200401   ok (non-closed singly connected)
    cone                200000   200401   ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (-0.02 -0.02 0) (0.02 0.02 0.0006983)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-3.56487e-17 -2.98897e-17 -2.97265e-15) OK.
    Max cell openness = 1.33522e-15 OK.
    Max aspect ratio = 177.943 OK.
    Minimum face area = 8.74406e-13. Maximum face area = 1.09776e-08.  Face area magnitudes OK.
    Min volume = 9.2687e-19. Max volume = 9.87975e-14.  Total volume = 5.7744e-07.  Cell volumes OK.
    Mesh non-orthogonality Max: 89.2769 average: 9.76535
   *Number of severely non-orthogonal (> 70 degrees) faces: 84000.
    Non-orthogonality check OK.
  <<Writing 84000 non-orthogonal faces to set nonOrthoFaces
    Face pyramids OK.
    Max skewness = 0.437164 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

Thanks
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