Hello all,

I am confronted with a strange problem, I have a fine mesh with a good quality which I have to extend and also to coarsen for run time reasons. The question is: is there a possibility in prostar or ICEM-CFD to coarsen my grid? At best with an aspect ratio. Any ideas?

Thanks, Nicola

Hey Nicola,
Is it a hex or tetra mesh? It will be difficult to modify your mesh in prostar. CJOIN combines two hex cells together, but you will have to do it by hand. With ICEM-CFD you cannot modify existing meshes. If you would have build it in ICEM, it would be easy to create a new (croasen) mesh. Did you try the AMG solver? The multi-grid approach (recommended for unstructured meshes) could bring some advantage, without modifying your mesh at all.
Greetings, Marc

Hi Marc,

it is hex, and I found in the star-manual the command "crse", which generates a coarser mesh from existing cells. Is there anyone who has tried it? Marc, have you checked how much time you can save with the AMG? I have a really complex grid with different cell types and a complicated geometry, to remesh will be my last alternative.

Regards,

Nicola

Hey Nicola,
I am not using the AMG for a long time now, so I don't have big experience. Of course the gain depends on the problem. I had a difficult case with bad convergence, where the gain was zero. And I had a restart job, which used to need 36 iterations to converge. This one converged after 11 iterations! It is very easy to test it. Just use SOLVE, SCALAR, AMG in prostar and do a starlink -x.
Greetings, Marc

Thanks for your answer, Marc.

My problem is still how to coarsen a mesh either in StarCD or with ICEM. There is a possibility in Star with the command crse, does anyone knows how it works?

Nicola

It works for structured hex meshes only, making one cell from 8 (i.e. reverse to cref 2,2,2)