• Problem 6.3b: GB2=zero(Uy-Vx) seems to work fine for some triangulations, but fails for others. (It always seems to work for 1D Galerkin problems). The PDE2D documentation does not suggest including derivatives of the solution inside the zero function (e.g., zero(Uy-Vx)= big_number*(Uy-Vx)), though it often works: here is one program for this problem that works. The free-slip boundary conditions given in Problem 1, Chapter 5, seem to be more reliable for 2D Galerkin problems.