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-   -   Negative Skew Volume in Unstructured Block (http://www.cfd-online.com/Forums/pointwise/114778-negative-skew-volume-unstructured-block.html)

Hybrid March 17, 2013 16:27

Negative Skew Volume in Unstructured Block
 
Hi,

I have tried to mesh a geometry for a week, hybrid topology (structured near the body and farfield in unstructured).

whenever I tried to solve unstructured block in initialized but producing negative skewness. It create trouble for me by displaying a message in Fluent "Mesh Check failed".


How to avid that??

taxalian March 17, 2013 17:17

Hi Ali,
:confused: sound strange.
1st Possibility:
---------------
make sure that your surface meshes confirms to the database i.e. all grid points on the geometry surface. Because it could happen sometimes that the symmetry plane or farfield surface mesh does not confirm to the database you loaded. When you try to initialize the unstructured block solver it gives you error.

2nd Possibility:
---------------
Pointwise/Gridgen generates pyramids at the prism and tetrahedral interface. So you may need to take care about your mesh quality in that region. Try to play with the boundary decay parameter.

If possible please share some sketches of your domain. May be one can recommend something better.

Arey yaar koshish karo ho jaey gaa! Good Luck.:)

cnsidero March 17, 2013 22:15

Where are you seeing the negative skewness error, in Pointwise or in Fluent?

Are you sure the error is in the unstructured block?

You should check the orientation of your structured blocks to make sure they're all right handed (ie. the IJK computational coordinates should make a right-handed coordinate system)?

-Chris

Quote:

Originally Posted by Hybrid (Post 414531)
whenever I tried to solve unstructured block in initialized but producing negative skewness. It create trouble for me by displaying a message in Fluent "Mesh Check failed".
How to avid that??


Hybrid March 18, 2013 17:09

I tried all the best possible options, successful in getting positive skew volume.

In Pointwise positive skew volume option enables only when an unstructured block is initialized.

I noticed the fluent accepts the mesh with negative skew volume.

Is there any best practice guide (topologies as in Ansys ICEM Workshops) to mesh aerodynamic configurations to simulate external air flow like fin body configurations ("+" or "X"), aircraft, etc.?


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