Dear all, Do you have any tips concerning the two questions below ? Thank you and best regards, Floriane ________________________________________ De : firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> de la part de Floriane Gidel [RPG] <mmfg@leeds.ac.uk> Envoyé : mardi 19 avril 2016 16:42:47 À : firedrake@imperial.ac.uk Objet : Re: [firedrake] use of BCs for interior nodes Yes this was just a simple case where phi_s has the same value everywhere (while in our case it will be updated only at the top surface), so in the example, I use neuman boundary conditions (u.n = 0 everywhere), and two Dirichlet boundary conditions : the top value of phi_s at the top of the domain, and the bottom value of phi_s at the bottom of the domain (since in this example, they are equal). This is why I ask the second question about using the top boundary of phi_s as a boundary condition for the bottom of the domain (as well as for the top surface). I hope this is more clear. Floriane ________________________________________ De : firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> de la part de Lawrence Mitchell <lawrence.mitchell@imperial.ac.uk> Envoyé : mardi 19 avril 2016 16:38 À : firedrake@imperial.ac.uk Objet : Re: [firedrake] use of BCs for interior nodes
On 19 Apr 2016, at 16:35, Onno Bokhove <O.Bokhove@leeds.ac.uk> wrote:
I missed that last week in the code:
the 2nd order equation dzz(phi) needs 2 conditions, chosen here to be the same at the top and bottom; also phi_s at later stages will be one of the unknowns! So how is it possible that the equation was solved at all with only one condition? Did it take Neumann condition at the bottom, as part of an automatic procedure in Firedrake?
A neumann condition just kills one of your surface terms when integrating by parts, no? If you just completely left it out, that's equivalent to choosing u.n = 0 as a neumann condition on that side. Lawrence _______________________________________________ firedrake mailing list firedrake@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/firedrake