Thanks for the update. I did try to assign a Dirichlet and Neumann condition to the same boundary for a simple diffusion problem and found that it doesn't work. I'm pretty sure what I did was mathematically well-posed, but FiPy didn't like it. I haven't worked my way through the matrix discretization to see why; Wheeler may know.
> On Apr 14, 2017, at 1:38 PM, James Pringle <[email protected]> wrote: > > Dear all -- > > I would like to withdraw my question. My blithe assertion that there had > to be a solution was naive. It turns out in going from a stream function to a > pressure formulation, my boundary conditions had become non-local. > > Thus fipy was not giving me a solution because there was no solution -- > which tends to give any solver fits. My apologies for wasted time. > > Jamie > > On Thu, Apr 13, 2017 at 3:10 PM, Pringle, James <[email protected]> wrote: > Dear all -- > > I need to solve a second order PDE in 2D of the form > > A(x,y)*(eta_xx+eta_yy)+B(x,y)*eta_x+C(x,y)*eta_y = 0 > > on a rectangular domain. On three sides there is a BC of no normal gradient. > On the fourth side their is a Cauchy boundary condition: > > @x=0, eta_x=D(y) AND eta=0 @x=0 > > Lets assume that there is a solution that meets these boundary conditions > (i.e. I have not screwed up). Should fipy be able to solve this by specifying > (both at the same place, x0side) > > var.constrain(0., where=x0side) > var.faceGrad.constrain(D_rank2, where=x0side) > > Or will this break the numerics? My actual problem is considerably more > complex, and I want to check that this is even plausible before starting down > this path. I can make this boundary simpler, but at the cost of considerable > complexity elsewhere. > > Thanks, > Jamie Pringle > > Director Ocean Process Analysis Laboratory in the Insitute for Earth, Ocean > and Space > Associate Professor of Earth Sciences > University of New Hampshire > http://oxbow.sr.unh.edu > > _______________________________________________ > fipy mailing list > [email protected] > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] _______________________________________________ fipy mailing list [email protected] http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
