dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

Quoting Pablo De Napoli <pdenapo@xxxxxxxxx>:

> Hi,
> 
> I want to ask a question about Dolfin. I need to solve an elliptic mixed
> boundary value problem
> with non-homogeneous Dirichlet conditions.
> 
> I've modified the example that comes with dolfin to do so.
> 
> Is it ok if I set the Dirichlet boundary condition like this...
> 
>  // Dirichlet boundary condition
>   class DirichletBC : public BoundaryCondition
>   {
>     void eval(BoundaryValue& value, const Point& p, unsigned int i)
>     {
>       real x = p.x();
>       real y = p.y();
>       if ( std::abs(y) < DOLFIN_EPS )
>         value = x*x;
>       else if ( std::abs(y - 1.0) < DOLFIN_EPS )
>         value = x*x+1.0;
>     }
>   };
> 
> 
> The program seems to work, but by doubt is because the set of functions that
> verify this
> boundary condition is not a vector space (but rather a linear manifold)
> (and I don't know if the code in Dolfin assumes that the boundary condition
> should be zero,
> as this is not documented in the manual)
>

If you don't set anything, DOLFIN assumes a zero Neumann boundary condition.

Garth

 
> best regards,
> Pablo
>