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dontknow August 30, 2007 15:53

Structure Analyis Open Foam

I read that openfoam uses finite volume method for stress analysis. can anybody explain what andvantages and disadvantages are there compares with "standard" fem.

thanks a lot

Tim August 31, 2007 06:05

Re: Structure Analyis Open Foam
STAR-CD has a similar capability.

There are three main advantages: 1. Meshing; 2. Model size (running parallel); 3. tight coupling between fluid/solid continua.

1. FEA packages have limits on the element types they can use (you must be able to define a shape function) so if you want to automatically mesh something, you have to use tets, whereas FV codes (if written correctly) can use elements with any number of faces (ie polyhedra). With tets, to mesh a complex geometry and get an accurate result requires a lot of elements. You can obtain the same level of accuracy, but computationally more efficiently with polys.

2. FEA packages don't scale (ie run on many CPUs) very well, and require a lot of memory, so 1 million elements is a big FEA model. As with CFD, FV codes, running cases with many millions of cells over many processors is trivial (so long as you have a big enough machine/license).

3. I don't know about OpenFoam, I guess it's the same, with STAR you can run the fluid and stress problem in the same model. Eg, for engine thermal analyses you can solve the fluid coolant, CHT and thermal stress problem at the same time - no mapping of results from one code to another - which helps for speed/accuracy of calculation.

Of course there are disadvantages too, eg FV stress doesn't deal with shell-like elements well, and it's pretty new technology so almost everyone uses fea packages for stress.

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