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-   -   [mesh manipulation] Does extrudeMesh affect mesh quality in non extruded cells? (https://www.cfd-online.com/Forums/openfoam-meshing/147114-does-extrudemesh-affect-mesh-quality-non-extruded-cells.html)

Blanco January 13, 2015 11:04
Does extrudeMesh affect mesh quality in non extruded cells?
 
2 Attachment(s)
Hello everybody,

I have a strange problem with a mesh I created through blockMesh.
The mesh is for a 2D case, you can find the blockMeshDict here attached.

After creating the mesh if I check its quality, using checkMesh utility, I get:

Code:
Checking geometry...
    Overall domain bounding box (-0.2 -0.9 0) (0.8 1.1 0.1)
    Mesh (non-empty, non-wedge) directions (1 1 0)
    Mesh (non-empty) directions (1 1 0)
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (-4.47678e-17 -3.69151e-18 -1.16236e-15) OK.
    Max cell openness = 1.76034e-14 OK.
    Max aspect ratio = 169.31 OK.
    Minimum face area = 3.27985e-09. Maximum face area = 0.00622355.  Face area magnitudes OK.
    Min volume = 3.27985e-10. Max volume = 0.000114482.  Total volume = 0.193475.  Cell volumes OK.
    Mesh non-orthogonality Max: 62.6561 average: 27.9759
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 3.23037 OK.
    Coupled point location match (average 0) OK.
...and everything seems ok.
After this, I want to extrude the mesh starting from the top and bottom boundaries, therefore I issue an extrudeMesh command using the extrudeMeshDict here attached. Everything seems to go well but if then I issue again the checkMesh command I get the following problems:

Code:
Checking geometry...
    Overall domain bounding box (-0.2 -10.9 0) (0.8 11.1 0.1)
    Mesh (non-empty, non-wedge) directions (1 1 0)
    Mesh (non-empty) directions (1 1 0)
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (2.07326944578e-16 5.89928008973e-19 -4.02186033899e-15) OK.
 ***High aspect ratio cells found, Max aspect ratio: 13192.513369, number of cells 5577
  <<Writing 5577 cells with high aspect ratio to set highAspectRatioCells
    Minimum face area = 3.27984629532e-09. Maximum face area = 0.02467.  Face area magnitudes OK.
    Min volume = 3.27984629533e-10. Max volume = 0.00087830134.  Total volume = 2.19347456322.  Cell volumes OK.
    Mesh non-orthogonality Max: 70.4886475638 average: 22.9159292824
  *Number of severely non-orthogonal (> 70 degrees) faces: 2.
    Non-orthogonality check OK.
  <<Writing 2 non-orthogonal faces to set nonOrthoFaces
    Face pyramids OK.
    Max skewness = 3.23049530527 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.

End
If I check where are the 2 severe non-orthogonal cells...I find that they are placed inside the non-extruded mesh! :confused: No problematic cell is placed in the newly extruded zone (apart high aspect ratio cells which were expected).

Does anyone have an idea why this is happening? Or does anyone have already seen this behavior?

Regards,

Blanco

Blanco January 23, 2015 10:54
Update -- SOLVED
 
I update the status for anyone who could have the same problem:

It works if you write in binary or increase your writePrecision.
In particular, the problem still appear even if you use ascii with 12 as write precision...therefore binary is strongly suggested.

wyldckat January 23, 2015 14:44
Greetings Blanco,

Many thanks for providing the solution to your issue!

For future reference, this was also reported as a bug here: http://www.openfoam.org/mantisbt/view.php?id=1497

Best regards,
Bruno

zhutaihang February 25, 2023 08:19
For someone having the same problem, if the suggestions from the above doesn't work, please try changing the extrudeModel into linearNormal.

I have been surfering from the same problem until I changed linearDirection into linearNormal.

Good luck!


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