No Onno, at the moment phis is a 3D function, phis(x,y,z), which is defined in the whole 3D domain but updated from the equations only at the surface z=H0. I would like to copy this update in the interior nodes. To include a 2D function phis(x,y) in the equations is a different problem (which might work as well, but it's not what we consider at the moment). Floriane ________________________________ De : firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> de la part de Onno Bokhove <O.Bokhove@leeds.ac.uk> Envoyé : jeudi 10 décembre 2015 17:16 À : firedrake@imperial.ac.uk Objet : Re: [firedrake] 2D to 3D function To rephrase that: The 2D function: phis(x,y) should become a 3D function: phis_extended(x,y,z) independent of z, i.e., its value does not vary in the z-direction but can vary in the horizontal and time. How does one do that in FD? ________________________________ From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of Floriane Gidel [RPG] <mmfg@leeds.ac.uk> Sent: Thursday, December 10, 2015 4:53 PM To: firedrake@imperial.ac.uk Subject: [firedrake] 2D to 3D function Dear all, First of all, thanks a lot for your time last Friday, and your help both for the implementation and for the installation of Firedrake. I am now trying to implement the equations we discussed on Friday, for the 3D potential flow equations. As a reminder, I solve the equations for phi, h, but also phi_s which is a 3D function, but is only updated at the free surface. However, I would like to update the interior nodes of phi_s as well, by copying the value of its surface nodes, as soon as they are updated (that is, simultaneously with solving the coupled equations). Is there a way to do this? I attach a short pdf summarising the equations, the current implementation and the issue I get. Thank you very much, Floriane