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-   -   Unstructured mesh (on Gridgen) doesn't run in FLUENT (http://www.cfd-online.com/Forums/fluent/109351-unstructured-mesh-gridgen-doesnt-run-fluent.html)

Santiago November 15, 2012 11:35

Unstructured mesh (on Gridgen) doesn't run in FLUENT
 
Hi Guys,

I'm not an expert using unstructured meshes on FLUENT. The thing is that I had to make a hybrid mesh (prisms + tets) amid my (3D structured) domain in an attempt to reduce the number of nodes. So what a I did was to extrude the unstructured mesh on the walls and to initialize an unstructured block on the core of the block.

When I run a 1st order SIMPLEC with a k-e closure, everything is fine. But when I try to shift gears to a 2nd order scheme the case automatically diverges. It doesn't even bother to make one time step.

Thanks in advance,

S

LuckyTran November 15, 2012 13:06

I would check grid quality and try to improve it as much as you can. For meshes with skewed cells can easily lead to those symptoms. Look for the cells between the prism layer and core mesh. This is usually where the skewed cells show up.

eishinsnsayshin November 16, 2012 13:46

I've heard SimpleC can have big issues with any skewness since it sets under-relaxation factors to 1 for convergence speed up....did you try using Simple?

LuckyTran November 16, 2012 14:02

Quote:

Originally Posted by eishinsnsayshin (Post 392590)
I've heard SimpleC can have big issues with any skewness since it sets under-relaxation factors to 1 for convergence speed up....did you try using Simple?

I don't think this is the case, since a 1st order scheme converged without difficulty, but one can always try and find out if there is time.

Santiago November 16, 2012 15:48

Quality
 
What would be a good quality criteria for unstructured meshes? The same as for structured (Jacobian/skewness centroid/aspect ratio)?


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