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Mesh quality after snappyHex

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Old   May 7, 2013, 04:59
Default Mesh quality after snappyHex
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i'm running the case of a flow inside a rough channel. I'm trying to generate a proper mesh. The bottom roughness is formed by small cubical blocks.

Each block's surface mesh should be formed by approximately 4 cells in the vertical direction and 2 cells in the two horizontal directions (although the refined cells should be about 2.5 units wide, while the blocks are 4.5 units wide, so a BIT LESS than 2 cells).

After snappyHex, however, i ran checkMesh and the result is the following
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                  
    in                  6410     6743     ok (non-closed singly connected)  
    out                 5600     5781     ok (non-closed singly connected)  
    left                18367    19132    ok (non-closed singly connected)  
    right               18367    19132    ok (non-closed singly connected)  
    top                 56000    56541    ok (non-closed singly connected)  
    bottom              510205   595645   ok (non-closed singly connected)  
    spires_patch0       46711    48691    ok (non-closed singly connected)  
    roughness_patch0    603177   690348   ok (non-closed singly connected)  
    hangar_patch0       38240    38481    ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-10 -7 -0.00139171) (30 7 4)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (3.74041e-16 1.31646e-15 -1.22914e-13) OK.
    Max cell openness = 4.21681e-16 OK.
    Max aspect ratio = 5.83191 OK.
    Minumum face area = 1.76458e-05. Maximum face area = 0.0200125.  Face area magnitudes OK.
    Min volume = 6.93409e-07. Max volume = 0.00200123.  Total volume = 2237.84.  Cell volumes OK.
    Mesh non-orthogonality Max: 57.4584 average: 12.2611
    Non-orthogonality check OK.
 ***Error in face pyramids: 7 faces are incorrectly oriented.
  <<Writing 7 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 7.12497, 102 highly skew faces detected which may impair the quality of the results
  <<Writing 102 skew faces to set skewFaces
    Coupled point location match (average 0) OK.
How can i improve the result?

I don't know if these informations are enough. If you need to know more i can post some screenshots or others dicts.

Thank you very much
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Old   May 10, 2013, 05:39
Akshay Kumar
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Hey Luca

Firstly check where these cells are located. Use foamToVTK -faceSet to write them in the vtk format and use paraview to view them. Then think of ways to refine those areas to get a better mesh.

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Old   May 15, 2013, 00:46
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Thanks Akshay. I will try this way
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