[Getfem-users] Evaluate solution at mesh nodes.

[Dawid Midura]

Hi all,

I am solving Helmholtz equation in a region laying in between two cocentric circles. I set Neumann type boundary data on the inner circle, and Robin type condition on the outer circle. . I want to compare the FEM solution with the analytic solution that I know to see if I coded the FEM solver correctly. To do so I compare both solutions at the boundaries of the domain. My question is, how do I evaluate the solution at a given mesh vertex? (I have both boundaries set as separate mesh regions) Here, I'm referring to the original, input mesh, not finite element mesh which in addition contains FEM nodes. I hope I said it right. Thus far I have used getfem::interpolator_on_mesh_fem object to evaluate the solution on the inner boundary, but I can't do the same for the outer circular boundary as most of that boundary lies outside of the computational domain (i'm using triangular elements), so what I did up to this point was picking points laying very close to the outer boundary but still in the computational domain and interpolated the solution at those. 

Thanks in advance,

Dawid M.