dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

Yes, look at the demo in src/demo/pde/dg/. (It contained some test
code before that I just removed.)

Yes, you can take the avg() and jump() of an arbitrary function (but
there may be some limitations that I can't recall right now).

It currently only works in 2D. In 3D, it only works in principle but
not in practice... :-)

What is currently holding us back from getting everything in place is

    (1) Decide on a numbering scheme for the mesh and write this down
        firmly in the manual

    (2) Implement this in FFC and DOLFIN

    (3) Porting FFC to generate UFC code

/Anders


On Mon, Jan 29, 2007 at 04:08:06PM +0100, Johan Hoffman wrote:
> Is there a demo-form file available for using these operators? Can one
> take the avg and jump of an arbitrary function?
> 
> /Johan
> 
> 
> 
> > What we have implemented for DG is the ability to define integrals
> > over interior facets that have contributions from both sides of the
> > facet, so you can write
> >
> >     v('+')*v('-')*avg(v)*jump(u, n)...
> >
> > It's a little different from what you have in that the integral is
> > over all interior facets in the mesh, not just along some given
> > surface.
> >
> > Perhaps you could extract all the cells in the mesh that border to the
> > common surface, so instead of having some interior surface, you have
> > an interior mesh that contains the surface and each interior facet in
> > that mesh connects to exactly two cells, one on each side.
> >
> > /Anders
> >
> >
> > On Thu, Jan 18, 2007 at 09:24:01AM +0100, Johan Hoffman wrote:
> >> Garth and Anders,
> >>
> >> I am interested in solving a problem where I a priori specifies an inner
> >> surface (aligned with cell faces) where the solution is discontinuous.
> >> The
> >> coupling of the solution over the discontinuity is taken cared of by a
> >> surface integral over that inner surface (like a penalty term).
> >>
> >> For this I expect to need:
> >>
> >> (1) a data structure with "double nodes" at a predefined surface (=
> >> collection of nodes/faces).
> >>
> >> (2) for the nodes on the surface; the ability to assemble only
> >> contribution from either side of the surface for the "double nodes"
> >> respectively (where the two sides of the surface may be represented by a
> >> MeshFunction for example).
> >>
> >> (3) a surface integral defined over an inner surface.
> >>
> >> I suspect that some parts of (1)-(3) is already in place, as part of the
> >> DG work? What remains to be done to handle this problem?
> >>
> >> /Johan
> >>
> >>
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> 
> 
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