Could you please refer to any examples of solving the first-order PDE with nonhomogeneous Neumann BCs? In the last version of the FF manual, I found a reference to the function int0d, but I don’t have a clue how to correctly incorporate it into the problem description.

Many thanks for your support and dedication to scientific computing,
Vlad

Could we solve a simple PDE-1, e.g., \nabla u(x,y) = g(x,y), using FE spaces other than P1 or P2 (here, we see the solution is numerically unstable)? E.g., we’ve found space P1b useful to solve the PDE and interpolate then the solution to the regular P2 or P1 for future use like in the example attached. Could you please recommend any other FE spaces for solving other PDEs of the first order? Thank you.