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-   -   Fluent: Mesh Adaption based on Gradient (http://www.cfd-online.com/Forums/fluent/77898-fluent-mesh-adaption-based-gradient.html)

enigma July 7, 2010 05:33

Fluent: Mesh Adaption based on Gradient
 
G'day Everyone,
I'm having a little difficulty with Fluent and its gradient mesh adaption tool. I have an unstructured mesh, based on quads, 3-dimensional which I adapt and refine in Fluent. The problem is, that Fluent would not let the cells be less than one quarter the size of the surrounding cells, no matter how many times I refine the mesh, it would always not only refine the cells with the high gradients, but also the surrounding cells. It somehow would not allow cells to be too different in their size.

One can see that in the attached example, cells are smaller where the gradient is high (pressure gradient in this case), however, 4 of those small cells are always the same size than 1 large cell. If I force Fluent to refine the mesh, it would qualitatively be the same ratio.


http://www.firebreed.de/FREEMIND/200..._shockwave.jpg


Does Anyone have some experience with this?
Can anyone help?

Thank you very much in advance!

enigma July 10, 2010 05:47

Mistake found - ANSYS RESULTS does not refresh the mesh data when I import a new case and dat file from Fluent. Fluent actually does refine properly. All fine now.

mahmohammad July 14, 2010 17:54

That's good that your problem is solved. :)

I have two questions: First of all, how can I increase the grid size? I tried coarsening but it doesn't work! I just want to increase the grid size.

And second: as it is obvious in the picture you attached, When I try to refine the mesh, Fluent divides each cell into four. How can I do it different? I mean how can i divide each cell into two or three cells?

Thanks a lot
Mahmohammad

enigma July 14, 2010 20:26

Fluent can't coarsen beyond the original mesh size. It can only coarsen where it has previously refined. Unfortunately, there's no way (I'm aware of) that you can modify the algorithm so that 1 cell is replaced by less than 8 cells (in 3D).

mahmohammad July 15, 2010 17:36

Ok!
that was not good news but thanks for responding!!:p

Mohammad


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