Jennifer,
Sure, here's what I came up with. From what I can see, it looks like the
difference between this program and test case 8 is the use of
HalfHyperShellBoundary.
After looking at it, this is sort of an awkward problem. What is
happening is that you are attaching the hypersphere boundary to boundary
indicator zero of your geometry. The problem is that as per the
documentation of the GridGenerator::half_hyper_shell function, by
default, *all* parts of the boundary have boundary indicator zero (but
this can be changed using the 'colorize' argument). This includes the
two faces in radial direction that terminate the half shell for which
this boundary description is definitely not appropriate.
What happens then is sort of a complex travesty: the no_flux function
wants to know the normal vectors of the two faces on the last cell of
the half circle that come together at the left terminating vertex; the
normal vectors at this point should have been
(-1, 0) (for the face on the outer radius)
(0, -1) (for the radial face that terminates the half-circle)
which at the common vertex span the entire space as expected. But, due
to the erroneous choice of boundary geometry, the second face believes
that it, too, is on the outer perimeter of the domain and also reports
(-1, 0)
which then leads through complicated machinations to the error message.
I don't really know how one could have caught this error up front. If
you hadn't computed no_normal_flux constraints, you would have noticed
upon inspection of the mesh after one refinement since there would have
been a mis-placed new vertex. In essence, however, the error message
simply says that something strange is happening that the library doesn't
understand, but there are too many ways something could have gone wrong
to actually point the finger at any one cause in the error message...
Does this make sense?
Cheers
W.
------------------------------------------------------------------------
Wolfgang Bangerth email: [email protected]
www: http://www.math.tamu.edu/~bangerth/
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