dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, May 11, 2010 at 10:11:04AM -0700, Johan Hake wrote:
> On Tuesday May 11 2010 06:48:04 Anders Logg wrote:
> > The advection-diffusion demo (both C++ and Python versions) says in
> > the comment that a stabilized method is used, but the stabilization
> > seems to be missing.
>
> Yes, it looks like the stabilization part is missing.
>
> > I think I remember this being added at some point, by either Hake or
> > Garth. Any clue where this went?
>
> I have mentioned adding a SUPG stabilized demo a while ago. I do not know who
> added this one, eventhough my name comes up on bzr annotate :P. It looks like
> it is Kristian who is the original author?
>
> > There also seems to be a typo for the diffusive term which appears in
> > both LHS and RHS.
>
> The diffusive term looks correct to me. Note that the advective term is _not_
> integrated by part. This implicitly sets a flux condition on the Neumann
> boundaries to:

Yes, it's correct:

a = v*u*dx + 0.5*k*(v*dot(velocity, grad(u))*dx + c*dot(grad(v), grad(u))*dx)
L = v*u0*dx - 0.5*k*(v*dot(velocity, grad(u0))*dx + c*dot(grad(v), grad(u0))*dx) + k*v*f*dx

I missed that +/-0.5*(...) aslo included the diffusive term.

--
Anders


>    dot(u*velocity,n)
>
> The diffusive flux across the boundaries are set to zero.
>
> Johan

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