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 Rajeev Dubey October 29, 2000 04:21

CFD

When should one use finite volume method as compared to finite difference and finite element methods. Please give pros & cons.

 John C. Chien October 29, 2000 15:47

Re: CFD

(1). For highly accurate results, use the finite difference method. (2). If you don't have a choice but to use a commercial cfd code, then there is not much you can do but to use the finite volume mehtod (most commercial cfd codes use finite volume methods). (3). If you think, fluid dynamics problems can be treated as a mathematical solution procedure such as the one used in structure analysis, then using the finite element method will make you feel that structure and fluid are unified like Einstein's theory. It takes a special kind of people to use finite element method for fluid mechanics problems. (4). The bottom line is : If the result is accurate and reliable, people will use it in the product design, and the specific method used is not an issue at all.

 kalyan October 30, 2000 13:21

Re: CFD

Those are very good points. I would add a couple of points more.

1. Finite volume codes can handle unstructured meshes more easily than the finite difference codes.

2. In general, it is easier to debug finite difference and finite volume codes since they work with real quantities, i.e. cell averages, fluxes, point values and actual spatial derivatives. FEM works with basis functions and amplitudes. Again, this may be because of my background in FD and FV volumes. I certainly do not contest an opinions to the contrary.

 Astrid November 10, 2000 08:29

Re: CFD

Dear John,

Could you be more specific on point (2) as commercial CFD codes based on FEM are available, like ANSYS. Why shouldn't one use such a code? Are you aware of strong limitations of FEM in CFD that you would like to share? Are there physical problems that can be solved using FVM but not using FEM? For example, I heard that FEM can not be used for turbulent calculations as in FEM it is impossible to keep epsilon positive. On the other hand ANSYS provides several k-e-turbulence models, so I am confused.......

And point (3) .... what kind of people do you mean? People with a FEM-mathematical background or people that believe that fluid and structure are unified?