On Tue, 4 Mar 2008, Maxime Debon wrote: > Looking for tips to check the correctness of Ke matrix and Fe vector > in an handbook, I found this rule : A0 * u'' = (A0 * u')' - A0' * u' > > This latest transformation must be taken into account to adjust a > non-constant coefficient to the diffusion term. It also explains why > the result was correct with a constant coefficient.
Oh! I didn't even think of that. Yeah; if the coefficient is outside both derivatives then you get an extra term from it when integrating by parts. I'm more used to terms like (A0*u')' (which doesn't give you an extra term) than I am to A0*u''. Double-check and make sure that the latter is really what models your physical system. Often conservation models have a conservation statement: D/dt(conserved) = div(flux) and a constitutive relation: flux = A*grad(conserved) In which case A really does end up inside one but not both derivatives in the strong form of the resulting equation. --- Roy ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
