Hi sfepy users!
I have a bit of trouble with evaluating surface fluxes when using the
poisson equation.
I have a spherical shell geometry, where the inner shell surface and the
outer shell surface are kept at two different potentials.
There is spherical symmetry, so the flux should be equally distributed on
the surface faces of each shell.
Also, the total flux for the two surfaces should be the same, except for an
opposite sign.
After solving the PDE the main variable field, t, looks fine, there is a
1/r dependence as expected.
But when I evaluate the surface fluxes on either the inner or the outer
shell there are both positive
and negative fluxes per face. For each sphere there are two positive flux
regions and two negative
flux regions.
I checked my surface normals and they look as expected, i.e. parallel to a
vector from the origo to the face
on the outer surface, and antiparallel on the inner surface.
I use the call
Surfaces_flux=pb.evaluate('d_surface_flux.i.Surfaces(coef.val,t)',
mode='el_eval',verbose=False)
to evaluate the flux.
I hope that there is someone who can point out the obvious and easy-to-fix
mistake i made...
Best regards
- Bjarke Dalslet