Felix,
I think I ran into another bug here, but there is always the possibilty that I
just tried to do something stupid. Therefore, before I post this on GitHub,
I'd like someone who knows what he/she is doing to have a look at that.
Outline of the Problem: Use Nedelec Elements to compute time-harmonic
Maxwell's Equation in 2D on a circle, with the Boundary condition of vanishing
normal component (that actually holds true for the magnetic B-field on the
surface of perfect electric conductor).
That can't be right. If you have the curl-curl equation, you need to use the
Nedelec element and can then only prescribe the tangential component only. If
you want to prescribe the *normal* component at the boundary, then you need
either an H_div element (such as the Raviart-Thomas element) or an H^1 element
(such as the regular Q_k elements) and the equation cannot be the curl-curl
equation.
The boundary conditions
compute_no_normal_flux_constraint(...) cannot be applied, yielding the error
at the end of the mail. A minimal-ish example of just the constructor of the
problem is attached.
The fact that the error message is not more descriptive is a bug, even though
the function cannot work in that context. Can you open a bug report for the
lack of an intelligible error message?
Another question: if I use a spherical manifold for the boundary before global
refinement, and try to set up the system with the working FESystem composite
element, the function compute_no_normal_flux_constraints crashes as well,
telling me that "I gave it a manifold instead of boundaries". I don't
understand how to handle that. In this case, I hope a short code snippet is
enough:
GridGenerator::hyper_ball(triangulation);
static const SphericalManifold<dim> bound;
triangulation.set_all_manifold_ids_on_boundary(1);
triangulation.set_manifold(1,bound);
triangulation.refine_global(3);
dof_handler.distribute_dofs(fe);
std::set<types::boundary_id> bd_id;
bd_id.insert(0);
VectorTools::compute_no_normal_flux_constraints(dof_handler,0,bd_id,constraints);
That is because of a historical wart we'd like to fix after the upcoming
release: we have two ways to describe geometries -- one is the Manifold class
that can be attached to cells, faces, and edges; and the other is the Boundary
class that can only be attached to boundary faces and edges via the
boundary_id tag. The function you call only works with the latter. But you use
the former. You will want to use the HyperBallBoundary class for the boundary.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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