dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Jan 15, 2008 at 12:23:30AM +0100, Murtazo Nazarov wrote:
> > On Mon, Jan 14, 2008 at 08:57:34PM +0100, Murtazo Nazarov wrote:
> >> > Is there an obvious high level way to implement normal flow type
> >> > boundary conditions or symmetry type boundary conditions?
> >> >
> >> > -gideon
> >> >
> >>
> >> If you mean slip boundary condition which for normal velocity, it is
> >> already implemented and soon will be available with UNICORN.
> >>
> >> The slip with friction is also implemented.
> >>
> >> /murtazo
> >
> > How is this implemented and for which element types? Maybe it can be
> > added to DOLFIN.
> >
> 
> It is implemented in the "stong" way as the Dirichlet BC. The idea is to
> put u*n = u1*n1 + u2*n2 + u3*n3 = 0, where u = (u1,u2,u3) velocity and n =
> (n1,n2,n3) normal to a boundary node. At the monent it works for simple
> (cylinder, cube, ...) and quite complex geometries (car), but we are
> testing it in different geometries. Then, it would be good to add it to
> DOLFIN.

I mean how do you translate u1*n1 + u2*n2 + u3*n3 = 0 into an equation
for the degrees of freedom (which may or may not be u1, u2, u3), which
types of finite elements does this work for and how do you modify the
linear system?

-- 
Anders