dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Feb 16, 2011 at 05:07:57PM +0000, 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.

It would be good to be able to approximate by a suitably scaled value
at a single vertex, either the closest vertex to a given point
specified by a vertex index.

--
Anders


> 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 ;).