Implement more boundary conditions in FEM: periodic / Neumann ≠ 0 / Robin
We have (untested, see #28 (closed)) Dirichlet conditions implemented for the Finite Element method. Neumann = 0 boundary conditions are natural conditions in FEM if no other boundaries are imposed. What is missing, for completeness, is
- periodic boundary conditions: this should just be a small change to the assembly loop
- Neumann ≠ 0 conditions: add option to have du/dx ≠ 0 on the boundary, may be a bit more complicated
- Mixed Dirichlet-Neumann (Robin) conditions: solution likely goes together with 2.