At this point, I need to figure out how to use this formalism to generate something like
\mathbf{\int v \cdot f}(x,y) \, dS, where \mathbf{f} is a user supplied function. Would it make sense to define something like:
a = ufl.inner(ufl.dot(ufl.cross(u,uh), n), z0) * ds ufl.inner(-ufl.dot(ufl.cross(u, uh), n), z1) * ds
to do this, where uh is a user defined vector function interpolated on V? (I tried it in the code you sent and it ran without a problem, but I need to verify that the result makes sense.)
Anyway, thanks heaps for the guidance! Good evening!