[firedrake] Boundary conditions

[David Ham]

Standard GMSH problem: if you have a physical line you also need a physical
surface or GMSH will drop all the interior elements from the output.

On Saturday, February 1, 2014, Cotter, Colin J <colin.cotter at imperial.ac.uk>
wrote:

>  Dear Firedrakers,
>   I decided to create another set of cohomology tests, this time with
> Dirichlet boundary conditions, since there is a nice result relating the
> kernels of the operators with and without Dirichlet boundary conditions
> (for the maths-curious, it's Poincare duality).
>
>   However, I can't get the boundary tags into Firedrake from gmsh. If I
> attempt to tag the boundary using "Physical Line" in gmsh (see bottom of
> this email for the .geo file), the line
> >>mesh = Mesh("annulus.msh")
> produces:
> *** ERROR ***
> Error message: Unsupported mixture of face/element types
>
> Removing the physical line makes the error message go away, so there is
> something wrong with that line.
>
> What have I done wrong?
>
> all the best
> --Colin
>
> Point(1) = {0, 0, 0, 1.0};
> Point(2) = {1, 0, 0, 1.0};
> Point(3) = {1, 1, 0, 1.0};
> Point(4) = {0, 1, 0, 1.0};
> Point(5) = {0.3333333333333, 0.3333333333333, 0, 1.0};
> Point(6) = {0.66666666666666, 0.3333333333333, 0, 1.0};
> Point(7) = {0.66666666666666, 0.66666666666666, 0, 1.0};
> Point(8) = {0.3333333333333, 0.66666666666666, 0, 1.0};
> Line(1) = {1, 2};
> Line(2) = {2, 3};
> Line(3) = {3, 4};
> Line(4) = {4, 1};
> Line(5) = {5, 6};
> Line(6) = {6, 7};
> Line(7) = {7, 8};
> Line(8) = {8, 5};
> Line Loop(1) = {1, 2, 3, 4};
> Line Loop(2) = {5, 6, 7, 8};
> Plane Surface(1) = {1,2};
> Physical Line(9) = {2, 3, 4, 1, 6, 7, 8, 5};
>
>

-- 
Dr David Ham
Departments of Mathematics and Computing
Imperial College London

http://www.imperial.ac.uk/people/david.ham
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