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[Gideon Simpson <grs2103@xxxxxxxxxxxx>]

I'm familiar with handling the Diritchlet conditions, and I see in the  
Assembler header file that there is a procedure for handling  
construction over subdomains.  I'm a little unclear about exterior vs.  
interior facet domains, which I understand to be the faces of the tets  
on the exterior of the domain vs. the faces of tets in the interior,  
and how to relate that to my dirichlet/neumann problem.

I think I've been able to work around it by using the mesh labels  
within the ffc by declaring

ds0 = Integral("exterior facet", 0)

and integrating against ds0, but I'd like to understand how to handle  
this inside of dolfin.

-gideon

On Mar 18, 2008, at 4:52 PM, Anders Logg wrote:

> On Tue, Mar 18, 2008 at 09:23:25PM +0100, Murtazo Nazarov wrote:
> > > That helps.  Suppose I want to apply such a condition on one part of
> > > the boundary and specify dirichlet conditions on another part.  I  
> > > have
> > > the different boundary regions identified with cell markers.  But  
> > > how
> > > I would apply such a cell filter in this context?
>
> For Neumann, send the MeshFunction defining the part of the boundary
> you want to integrate over to the assembler (see Assembler.h). For
> Dirichlet, send the MeshFunction defining the part of the boundary you
> want to set the condition on to the constructor of DirichletBC.
>
> --
> Anders
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