dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Wednesday 09 April 2008 14:49:03 Dag Lindbo wrote:
> Johan Hake wrote:
> > Hello!
> >
> > I am simulating the diffusion of Calcium ions within an electrical field,
> > i.e., solving the Diffusion Advection (Convection) equation. The field is
> > not solenoidal.
> >
> > This workes fine for fields with small absolute values. When the typical
> > field get above a certain value, the solution starts to behave
> > peculiarly. It converges but I get negative values of concentration and
> > it becomes very dependent on the mesh size.
> >
> > My bilinear Diffusion Advection form with homogenous Neumann boundaries
> > look like: (skipping konstants)
> >
> > ( dot(grad(v),grad(u)) + u*dot(E,grad(v)) )*dx
> >
> > where v is the test function, u trial function and E the electrical
> > field.
> >
> > Having basic FEM knowledge, I have heard of the stabilizing method of
> > Petrov-Galerkin, but I have no experience using it. I found some very
> > usefull explainations in Dag Lindbos Master thesis :).
>
> Wow, you found that!
>
> > Do you think this method could be usefull to try out? If so, how should
> > this be formulated in FFC.
>
> Yes, SU/PG is very solid. I believe I cite the original paper if you
> need the details. As I recall, Garth has published papers on this topic.

Yep, I read some of the stuff

> In any case, there used to be a convection/diffusion module in DOLFIN.
> It contains both the forms and routines needed to compute the
> stabilization. Take a look under src/modules/convdiff/dolfin/ in DOLFIN
> 0.6.4. It was probably Garth who wrote this module.

Many thanks!

I will look into that form file!

Johan

> Cheers!
> /Dag
>
> > Many thanks in advance!
> >
> >
> > Johan
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