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-   -   FEM vs FDM (http://www.cfd-online.com/Forums/main/4274-fem-vs-fdm.html)

 Jack January 10, 2002 14:25

FEM vs FDM

Can we use FEMs for flow analysis?

 andy January 10, 2002 16:38

Re: FEM vs FDM

Yes.

 P.Fonteijn January 10, 2002 18:23

Re: FEM vs FDM

Discontinuites, like shocks, are hard to describe. And, don't expect any speed up compared to FDM. FEM is as slow as FDM.

Pascale

 cfd user January 10, 2002 22:18

Re: FEM vs FDM

There are many existing commercial codes which use FEM as their discretization. It will tend to be slower as mentioned in another response but literature shows it to be more accurate, requiring less grid points then FDM or FEM. Links between a FEA solver and CFD solver can be made with the finite element technique. It will probably be the way some day.

 Ist January 11, 2002 01:40

Re: FEM vs FDM

Dear all,

How about with FVM ? I think it is more stable solution compared with FDM. But, what's your comment ?

 kenn January 16, 2002 17:31

Re: FEM vs FDM

if it's an old FEM software, I guess it can't solve convetion dominating flow problems very well, because of stability issue.

but in fluid mechanics, todays' finite element kind methods are much better than FDM

 kenn January 16, 2002 17:48

Re: FEM vs FDM

all FEM, FDM, FVM, and spectral element methods are special forms of weighted residue methods. none of them are better method for every problems. by logic, FV must have disadvantages. it's stable due to it's local control of conservation, which is obviously better than global control; it treats complex gemotry much better than FD, which has to use boundary fitted coordinates or transformation to another space(computational space). so, FV is a general-purposed method. so why still FD?

I guess, for many problems, FV lacks accuracy.

FD could converge much faster than both FV and FE for many problems.

Spectral element converges even faster, however, in each step it costs more time to do integration( I guess) something like that.

also, FD is the easiest method to implement. BEM(boundary element) is the fastest method.

so, I'll say, if a problem can be solved using FD or BE gracefully, then use them; otherwise, consider the other three methods.

 Herve January 17, 2002 09:11

Re: FEM vs FDM

Look at the book edited by 33. Wendt, J.F., (1996), "Computational Fluid Dynamics  An Introduction", Springer. or the paper by Idelsohn, S.R., Oņate, E., (1994), "Finite Volumes and Finite Elements: Two 'Good Friends'", Int. J. num. Meth. Eng., Vol. 37, pp. 3323-3341. for a comparison. the advantage of FVM is that it is easy and fast to compute, and mass conservative (something more difficult to achieve with FEM I believe).

 Scott January 18, 2002 19:13

Re: FEM vs FDM

www.cfdesign.com

 Ist January 21, 2002 03:04

Re: FEM vs FDM

I think those method (FEM, FDM and FVM) has disadvantage and advantage. No method has not disadvantages. Ok

 yangqing January 27, 2002 11:42

Re: FEM vs FDM

now is FVM , one fdm method

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