On Wed, Feb 16, 2011 at 09:21:23AM -0800, Johan Hake wrote: > On Wednesday February 16 2011 09:07:57 Garth N. Wells wrote: > > On 16/02/11 16:54, Johan Hake wrote: > > > Question #145534 on DOLFIN changed: > > > https://answers.launchpad.net/dolfin/+question/145534 > > > > > > Johan Hake proposed the following answer: > > > > > > On Wednesday February 16 2011 08:48:38 Anders Logg wrote: > > >> Question #145534 on DOLFIN changed: > > >> https://answers.launchpad.net/dolfin/+question/145534 > > >> > > >> Status: Open => Answered > > >> > > >> Anders Logg proposed the following answer: > > >> > > >> On Tue, Feb 15, 2011 at 10:30:06PM -0000, Yi Jiang wrote: > > >>> New question #145534 on DOLFIN: > > >>> https://answers.launchpad.net/dolfin/+question/145534 > > >>> > > >>> Hi all, > > >>> > > >>> I am using the dolfin to solve a PDE problem by finite element method. > > >>> However, I met a problem when I try to define the linear form L(v) of > > >>> right hand side. Suppose the PDE is: > > >>> > > >>> F(x) = f. > > >>> > > >>> What should I do if the f is a Dirac Delta function. How to define it > > >>> in ufl? Anybody met and solved the similar problems before? > > >>> Thank you for attention and kind help. > > >> > > >> This is not supported. > > > > > > I am also interested in this. What would it require to implement? Changes > > > to UFL, FFC, DOLFIN? > > > > A lot of changes. It would require being able to integrate over > > surfaces/lines within a cell. > > > > UFL can be stretched to do this, but extentions to FFC and DOLFIN are > > needed. Take a look at the modelling discontinuities chapter in the > > FEniCS book ;). > > Looking forward to do that! > > A naive thought would be to introduce a DeltaDiracFunction which evaluates to > zero for all but a given coordinates which need to coincide with a vertex. But > I guess we need to prevent DOLFIN to interpolate the function during assemble, > and just evaluate it at the quadrature points, where it evaluates to zero? > > Johan
Anyone interested in this, please add a blueprint so we can remember it for later. -- Anders _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
