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[ICEM] How to deal with negative quality mesh elements in ICEM CFD mesh?

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Old   September 19, 2022, 07:04
Default How to deal with negative quality mesh elements in ICEM CFD mesh?
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Murali Krishnamraju
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I am trying to develop a Hexa mesh in a flow domain with a cylinder in a scour hole. The flow domain is shown below.

The bottom surface and the cylinder surface are treated as walls, and hence the inflation layers are provided around them.

The developed mesh contains some negative quality elements at the intersection of the cylinder with the bottom surface.

How can I remove those cells from the mesh?

I tried pre-mesh smoothing but was unable to remove them.

Please find the figures below

Domain.jpg

bottom_and_cylinder.jpg

Blocking.jpg

blocking1.jpg

low_quality.PNG
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Old   September 20, 2022, 05:10
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Gert-Jan
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Difficult to say. In my experience, the best results are obtained if the points and curves of a geometry match with the vertices and edges of the blocking structure. In your second figure I see 2 curves on the cilinder. These are not aligned with the 4 edges on the cilinder of the blocking structure. Therefore, create 2 more curves (and points) and make sure these are aligned with the edges by rotating all curves and points by 45.

Also, show a picture of the pre mesh on the surfaces. These might tell a lot on wrong projection. Regarding this projection, first create a pre mesh without projection. If this works okay, then mesh with edge projection, and then withh surface projection. In this way it might become easier to see where the problems occur.
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Old   September 27, 2022, 03:46
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Murali Krishnamraju
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Thank you for the response,
The cylinder has four curves and each curve is associated with an edge around the cylinder.
Coming to the premesh, I am giving a number of nodes to each edge and then generating the mesh and then converting it into an unstructured mesh.
I am exporting that mesh to fluent to run the simulation.

Is there any other way to generate the hexa pre mesh in ICEM CFD?
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Old   September 27, 2022, 06:35
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If I zoom into your picture, I see edges (black) from your blocking structure and curves (blue) from your geometry. They are 45 rotated from each other so they are not aligned. This might lead to problems.
I suggest to delete the curves and points on the cilinder and have the vertices associate on the curve the top of the cilinder and associate the edges with the outer surface.
If this does not work, create new curves and points where you want the edges and vertices to be.
Attached Images
File Type: png corve&edges.png (62.6 KB, 7 views)
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hexa blocking, hexa meshing, hexaedral meshes, icem 19.2, icem cfd

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