On Thu, Jun 12, 2008 at 2:37 PM, Anders Logg <[EMAIL PROTECTED]> wrote: > On Wed, Jun 11, 2008 at 08:11:56AM -0400, mspieg wrote: >> Hi all, >> is there a simple way to implement a known constant vector (e.g. the unit >> vector jhat = [ 0 1]') into a FFC form? >> >> my specific issue is that the right hand side of my PDE looks like >> >> -\Div f\jhat = - df/dy >> >> where f(x,y) is a user defined scalar function (and df/dy is not easily >> evaluated) >> >> Given a test function v, the weak form (in pseudo-latex) is >> >> \int dv/dy f dx - \int v f \jhat\dot ds >> >> The question is how to evaluate the 2nd term in the FFC form language (the >> volume integral works fine as v.dx(1)*f*dx) >> >> ideally something like >> >> jhat=?? >> L = v.dx(1)*f*dx) - v*f*jhat*ds >> >> (or more generally for a known unit vector k L=dot(grad(v),k)*f*dx - >> v*f*k*ds >> ) >> >> would be nice (in the same way as simple known constants can be built in >> directly) >> >> But I'm flexible...all help greatly appreciated >> marc > > It looks like you expect ds to be a vector. It's not. It's a scalar.
But you can get the surface normal as a vector, right? I think that is what Marc wants. Matt > -- > Anders > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.6 (GNU/Linux) > > iD8DBQFIUXr4Qp2CVMGvcgcRAkzUAJ0RBgD/M3qTRMsLolrgGZa9twknawCferA+ > p4dCQdvQsKhVkRwvpFXHq6w= > =SqMU > -----END PGP SIGNATURE----- > > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
