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Old   March 16, 2017, 16:09
Default cfMesh questions
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badoumba
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Hi everyone!

I have a bunch of questions regarding cfMesh, if anyone has any input for me.

- for external aerodynamics, I am starting with a stl file consisting of the object to study that I put within a box. Can we use cfMesh in combination with blockMesh so I just need a stl file with my object instead? I tried by running blockMesh first and then cartesianLMesh but at the end paraFoam opens only the initial blockMesh mesh and not the cartesianMesh buit one.

- The mesh seems cleaner than the one I had with sHM, but surprisingly checkMesh reports a lot of errors, especially negative volume (wichever untangleLayers boolean value set), extremely high ratio cells and number of edges not aligned with or perpendicular to non-empty directions. Is there any quality control system coupled?

- If I don't need especially low y+ and decide to go for a coarser mesh, it turns out to be very irregular at some sharp or curved parts. It seems that there is no "snapping" like in sHM (surfaceProjection but not exactly the same end result) o we have cells not fitting perfectly the surface which has an impact on any final visual. Only solution is to go for finer resolution. Any feedback regarding this point? Can we apply a sHM snapping step on top of a cfMesh (I know that for cartesian Mesh there is a default layer, might be a problem).

- Is there any diagnosis tool like layer coverture ?

Thanks guys !

Last edited by badoumba; March 17, 2017 at 03:10.
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Old   March 17, 2017, 04:29
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Regarding the second point, here is the detail of the errors I had so far.

To be sure, I initially run a surfaceCheck on my stl object, reporting no errors.
Below are the cfMesh steps in sequence and the corresponding checkMesh report.

Despite of my stl mesh being OK, I already have an error at first step
Code:
 ***Faces not in upper triangular order.
Things get worse starting from patchAssignment step.

Almost fixed at the end but I still have
Code:
***Number of edges not aligned with or perpendicular to non-empty directions
1-templateGeneration
Code:
Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 254379 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
            defaultFaces   132282   131761  multiply connected (shared edge)
  <<Writing 785 conflicting points to set nonManifoldPoints

Checking geometry...
    Overall domain bounding box (-2.6 -1.83559 -2) (2.6 3.76441 2)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (3.09535e-16 6.5087e-15 -4.18046e-14) OK.
    Max cell openness = 3.46945e-16 OK.
    Max aspect ratio = 1 OK.
    Minimum face area = 3.90625e-05. Maximum face area = 0.04.  Face area magnitudes OK.
    Min volume = 2.44141e-07. Max volume = 0.008.  Total volume = 116.277.  Cell volumes OK.
    Mesh non-orthogonality Max: 25.2394 average: 9.8424
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.333333 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.
2--surfaceTopology
Code:
Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 253870 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
            defaultFaces   129678   129662      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.6 -1.83559 -2) (2.6 3.76441 2)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (3.09745e-16 7.2506e-15 -4.1341e-14) OK.
    Max cell openness = 3.46945e-16 OK.
    Max aspect ratio = 1 OK.
    Minimum face area = 3.90625e-05. Maximum face area = 0.04.  Face area magnitudes OK.
    Min volume = 2.44141e-07. Max volume = 0.008.  Total volume = 116.277.  Cell volumes OK.
    Mesh non-orthogonality Max: 25.2394 average: 9.85378
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.333333 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.
3-surfaceProjection
Code:
Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 253870 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
            defaultFaces   129678   129662      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.6 -1.83559 -2) (2.6 3.76441 2)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (3.57253e-16 7.31184e-15 -4.13817e-14) OK.
    Max cell openness = 3.46945e-16 OK.
    Max aspect ratio = 1 OK.
    Minimum face area = 3.90625e-05. Maximum face area = 0.04.  Face area magnitudes OK.
    Min volume = 2.44141e-07. Max volume = 0.008.  Total volume = 116.277.  Cell volumes OK.
    Mesh non-orthogonality Max: 25.2394 average: 9.85378
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.333333 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.
4-patchAssignment
Code:
Checking topology...
    Boundary definition OK.
 ***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 253870 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
                   inlet      520      567  ok (non-closed singly connected)
                  outlet      520      567  ok (non-closed singly connected)
                     top      728      783  ok (non-closed singly connected)
                  bottom      728      783  ok (non-closed singly connected)
                    left      560      609  ok (non-closed singly connected)
                   right      560      609  ok (non-closed singly connected)
                      ws   126062   126044      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.48853 -1.64886 -1.91) (2.48853 3.57767 1.91)
    Mesh has 0 geometric (non-empty/wedge) directions (0 0 0)
    Mesh has 0 solution (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 383367
  <<Writing 211533 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (1.10492e-16 -5.47885e-16 3.57502e-16) OK.
    Max cell openness = 9.79989e-16 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 6.03942e-08. Maximum face area = 0.04.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -3.50553e-08, Number of negative volume cells: 428
  <<Writing 428 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 179.732 average: 17.4551
   *Number of severely non-orthogonal (> 70 degrees) faces: 14193.
 ***Number of non-orthogonality errors: 249.
  <<Writing 14442 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 6792 faces are incorrectly oriented.
  <<Writing 6702 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 391.705, 806 highly skew faces detected which may impair the quality of the results
  <<Writing 806 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 6 mesh checks.
5-edgeExtraction
Code:
Checking topology...
    Boundary definition OK.
 ***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 253870 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
                   inlet      520      567  ok (non-closed singly connected)
                  outlet      520      567  ok (non-closed singly connected)
                     top      728      783  ok (non-closed singly connected)
                  bottom      728      783  ok (non-closed singly connected)
                    left      560      609  ok (non-closed singly connected)
                   right      560      609  ok (non-closed singly connected)
                      ws   126062   126044      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.48853 -1.64886 -1.91) (2.48853 3.57767 1.91)
    Mesh has 0 geometric (non-empty/wedge) directions (0 0 0)
    Mesh has 0 solution (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 390796
  <<Writing 216335 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (-2.16088e-16 1.9379e-16 1.6233e-16) OK.
    Max cell openness = 1.19107e-15 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 2.86707e-08. Maximum face area = 0.0400005.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -2.92435e-08, Number of negative volume cells: 388
  <<Writing 388 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 179.309 average: 17.6868
   *Number of severely non-orthogonal (> 70 degrees) faces: 15224.
 ***Number of non-orthogonality errors: 293.
  <<Writing 15517 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 6619 faces are incorrectly oriented.
  <<Writing 6564 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 4472.82, 803 highly skew faces detected which may impair the quality of the results
  <<Writing 803 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 6 mesh checks.
6-boundaryLayerGeneration
Code:
Checking topology...
    Boundary definition OK.
 ***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 320421 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
                   inlet      616      667  ok (non-closed singly connected)
                  outlet      616      667  ok (non-closed singly connected)
                     top      840      899  ok (non-closed singly connected)
                  bottom      840      899  ok (non-closed singly connected)
                    left      660      713  ok (non-closed singly connected)
                   right      660      713  ok (non-closed singly connected)
                      ws   126062   126044      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.48853 -1.64886 -1.91) (2.48853 3.57767 1.91)
    Mesh has 0 geometric (non-empty/wedge) directions (0 0 0)
    Mesh has 0 solution (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 775711
  <<Writing 346064 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (-1.90407e-16 4.27573e-16 -5.45906e-17) OK.
    Max cell openness = 3.07327e-15 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 4.9538e-09. Maximum face area = 0.0400005.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -0.00346874, Number of negative volume cells: 42662
  <<Writing 42662 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 180 average: 32.083
   *Number of severely non-orthogonal (> 70 degrees) faces: 78889.
 ***Number of non-orthogonality errors: 75956.
  <<Writing 154845 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 262224 faces are incorrectly oriented.
  <<Writing 199176 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 38434.2, 9959 highly skew faces detected which may impair the quality of the results
  <<Writing 9959 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 6 mesh checks.
7-meshOptimisation
Code:
Checking topology...
    Boundary definition OK.
 ***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
    Cell to face addressing OK.
    Point usage OK.
 ***Faces not in upper triangular order.
  <<Writing 320421 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
                   inlet      616      667  ok (non-closed singly connected)
                  outlet      616      667  ok (non-closed singly connected)
                     top      840      899  ok (non-closed singly connected)
                  bottom      840      899  ok (non-closed singly connected)
                    left      660      713  ok (non-closed singly connected)
                   right      660      713  ok (non-closed singly connected)
                      ws   126062   126044      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.48853 -1.64886 -1.91) (2.48853 3.57767 1.91)
    Mesh has 0 geometric (non-empty/wedge) directions (0 0 0)
    Mesh has 0 solution (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 1890761
  <<Writing 677021 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (-3.5724e-17 -8.48847e-17 1.1956e-16) OK.
    Max cell openness = 4.10648e-16 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 6.69045e-07. Maximum face area = 0.0412546.  Face area magnitudes OK.
    Min volume = 1.15326e-09. Max volume = 0.00883498.  Total volume = 99.1529.  Cell volumes OK.
    Mesh non-orthogonality Max: 81.2189 average: 13.6253
   *Number of severely non-orthogonal (> 70 degrees) faces: 169.
    Non-orthogonality check OK.
  <<Writing 169 non-orthogonal faces to set nonOrthoFaces
    Face pyramids OK.
    Max skewness = 2.78854 OK.
    Coupled point location match (average 0) OK.

Failed 2 mesh checks.
8-boundaryLayerRefinement
Code:
Checking topology...
    Boundary definition OK.
 ***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
    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
                   inlet      616      667  ok (non-closed singly connected)
                  outlet      616      667  ok (non-closed singly connected)
                     top      840      899  ok (non-closed singly connected)
                  bottom      840      899  ok (non-closed singly connected)
                    left      660      713  ok (non-closed singly connected)
                   right      660      713  ok (non-closed singly connected)
                      ws   126062   126044      ok (closed singly connected)

Checking geometry...
    Overall domain bounding box (-2.48853 -1.64886 -1.91) (2.48853 3.57767 1.91)
    Mesh has 0 geometric (non-empty/wedge) directions (0 0 0)
    Mesh has 0 solution (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 1890763
  <<Writing 677019 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (2.50854e-17 -1.33239e-16 -1.45375e-16) OK.
    Max cell openness = 3.29611e-16 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 6.74561e-07. Maximum face area = 0.0412546.  Face area magnitudes OK.
    Min volume = 2.91116e-09. Max volume = 0.00883498.  Total volume = 99.1529.  Cell volumes OK.
    Mesh non-orthogonality Max: 69.883 average: 13.0992
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 2.6205 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.
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Old   March 17, 2017, 04:40
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Regarding the third point, here is a screenshot of what I am refering to.
In white is my edges.vtk

Thanks
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Old   March 17, 2017, 04:46
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And for the first point (sorry not being in order), my concern is how to set a symmetry patch in a model with cfMesh. Did'nt find any related tutorial or procedure.
Should I force my side mesh to Symmetry type in renameBoundary dictionnary?

Sorry to spam, I'm done

update :
Answering my own question, sharing it

Wall symmetry is implemented as following:


renameBoundary
{
newPatchNames
{
right
{
newName symmetry_plane;
type symmetry;
}
}
}

Last edited by badoumba; March 17, 2017 at 07:22.
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