From: Adam C P. IV <haz...@de...> - 2008-08-13 00:22:27
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On Tue, 2008-08-12 at 17:31 -0500, Kirk, Benjamin (JSC-EG) wrote: > I will see about sending you a patch to ex9 demonstrating SUPG for a > scalar problem. John is right, for systems it gets a little too > complicated for an example... Thanks, I'd appreciate it! > > ----- Original Message ----- > From: lib...@li... > <lib...@li...> > To: Adam C Powell IV <haz...@de...> > Cc: lib...@li... > <lib...@li...> > Sent: Tue Aug 12 17:19:46 2008 > Subject: Re: [Libmesh-devel] Example code with upwinding > > On Tue, Aug 12, 2008 at 5:15 PM, Adam C Powell IV > <haz...@de...> wrote: > > [Sorry to post a -users message to -devel; I can't post to -users.] > > Interesting. I can see about adding you to the list, if you want? Or > is it just an issue with your domain? Strangest thing: I'm a member of the list, and get all of its posts, and had no trouble posting through 7/15. Then 7/21 my posts started vanishing without showing up on the list. And I can still post to -devel just fine. But I think you (John) were a part of that discussion a week or two ago. > > I have a very high-Peclet number advection-diffusion problem, and > would > > like to use upwind differencing for the advection terms to reduce > > numerical diffusion. I don't see this in any of the libmesh > examples, > > but the online gallery shows some nice examples which might have > used > > it. (Also the deal.II FEA library has an example or two which uses > it.) > > AFAIK, upwind differencing *adds* numerical diffusion, to improve > stability. Right, uh, that's what I meant. :-) > > Is any libMesh code available with upwinding? > > I have some code which uses SUPG but it's not simple enough to be an > example. Nothing using simple upwinding though. Was this in 1D, 2D, > 3D? Maybe the dealII example could be co-opted to work in libmesh? This is example 12, in arbitrary dimensions; intro.dox ends with: Finally, we note that the program is dimension independent, i.e. after replacing <code>DGMethod<2></code> by <code>DGMethod<3></code> the code runs in 3d. The API is somewhat different, and this example's documentation makes it sound more FV-ish than FEA-ish. So I think it would be hard to translate. Frankly, I find the libMesh API, examples, and documentation easier to learn and more intuitive. But then, perhaps that's why you don't have an example with upwinding! Thanks again for the replies. -Adam -- GPG fingerprint: D54D 1AEE B11C CE9B A02B C5DD 526F 01E8 564E E4B6 Engineering consulting with open source tools http://www.opennovation.com/ |