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aunola July 16, 2008 03:31

Hello, I'm contemplating up

I'm contemplating upgrading my OF-1.4.1 to OF-1.5 because the new meshing utility snappyHexMesh could be useful for my aerodynamics simulations. However, upon reading the UG I was left with some unanswered questions. One of them is this:

For parallel runs I use MeTiS (keyword method in the decomposeParDict) for domain decomposition because I have a need for load balancing. MeTiS can only partition 3D meshes consisting of either hexahedra or tetrahedra. Yet the new meshing utility snapphyHexMesh will/may create split-hexes. Since these are different than hexes, my guess is such a mesh would be beyond MeTiS' capabilities.

Is that true ?

Thanks, Martin

bastil July 16, 2008 08:20

I am not sure but I think this
I am not sure but I think this should work with Metis. I have another question:
What about requirements of the input surface. This must be stl. However, what about free edges, T-Joints, ... in the input surface mesh? Does it have to be 100% clean and watertight or only representing my geometry?
If I take a look at the motorcycle example I see that tis stl has some free edges and kconsists of different parts. However, it does not look like an direct CAD-export at all.


olesen July 16, 2008 08:28

Martin, Where did you see t

Where did you see that Metis handles particular cell types? AFAIK it partitions graphs. For cfd/fem meshs these graphs should arise from the cell/element connectivity. I don't know enough to know how they build the graphs for networking and circuits, but I think it's safe to say that they don't have any cell types in those cases!

Anyhow Metis works fine with polyhedral meshes, both in OpenFOAM and STAR-CD.

eugene July 16, 2008 09:09

To work in parallel the decomp
To work in parallel the decomposition method for the mesh generator has to be parallel-aware. The methods currently available are hierarchical and parMetis afaik.

aunola July 16, 2008 09:16

Mark, This is specified in

This is specified in the manual for MeTiS 4.0 for the mesh partitioning routines (p.34-35). Whereas the graph partitioning routines obviously don't care about element types, the mesh partitioning routines are restricted as I mentioned in my original post. It seems then that OF does not employ the mesh partitioning routines of MeTiS.

Thanks for your reply.

fra76 July 16, 2008 09:41

I confirm what Eugen says. Onl
I confirm what Eugen says. Only parMetis and hierarchical are available for running snappyHexMesher in parallel.
However, with metis algorithm in OpenFOAM you can partition any kind of mesh. Try it!


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