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-   -   [ICEM] Recommened order for building volume mesh (http://www.cfd-online.com/Forums/ansys-meshing/67776-icem-recommened-order-building-volume-mesh.html)

siw August 26, 2009 06:04

[ICEM] Recommended order for building volume mesh
 
Hi,

I've made a mesh of a wing using the Octree method and applied smoothing to get a Quality of over 0.3. 8 elements are between 0.25 and 0.3, but I guess that's not too bad out of about 14 million.

Anyway, which of these two approaches would be best?

1). Run a new volume mesh using the TGrid option from the Octreee surface mesh, smooth that (if needed) and then apply the prism layers.

2) Apply the prism layer, then re-generate the volume mesh using TGrid and smooth if needed?

Thanks

cbr August 27, 2009 09:16

I turned to hexa meshes long time ago, but I would choose first variant

PSYMN August 27, 2009 11:59

First one is better, but for the tetra, not the prisms.
 
I would agree with CBR, for a simple geometry like a wing, and especially such a large mesh, Hexa would be much better than tetra prism and not very much work (might even be faster start to finish). On a complex model, Tetra/prism might have the speed advantage and might even outweigh the quality advantage of hexas.

But if you are stuck with Tetra/Prism, I would recommend the first approach. Actually, that TGrid hookup to 11.0 was not done very well (doesnít keep prisms, doesnít respect density boxes, etc.). For 12.0, we added a TGLib option to the Delaunay approach, which is much better. At 12.1, we have an option for AFT also (but that doesnít help you until November ;^).

Delaunay Tetra fill (TGrid is a brand of Delaunay) is better than Octree for CFD because it more efficiently fills the volume and because its cell to cell volume transitions are better.

I donít think it affects prism, but prism can affect the Delaunay. As prism grows in, the inside triangles may be of lower quality than the outside surface was. They can be stretched or squished in one direction by convex or concave situations.

So, if you planned to fill with Delaunay tetra anyway, it is better to do it from the Laplace smoothed outer envelope than after prism reduces the quality.

siw August 28, 2009 02:37

PSYMN, thanks again.

Unfortunately, I only have the tetra/prism licences - not hexa licence so I cannot make any these or multi-block meshes.

In addition, maybe you can help with this add-on question.

I have 2 dual-core processors in my PC so I have set Settings/General/Number of Processors to 4. When I use the Octree volume mesh I can see from Windows Task Manager that all are being used. But when I then use T-Grid only 1 processor is being used.

How can I make ICEM use all the processors with T-Grid?

Cheers.

PSYMN August 28, 2009 08:23

not yet
 
I understand, you can only use what you have...

As for parallel, the refinement portion of ICEM CFD Octree Tetra is parallel, but TGrid is not parallel.

They are working on it, maybe next year.

Simon


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