Hello, Sorry for the bother but I have a simple question to ask. I am currently developing some code to solve for wind-driven gyres and basin modes using QG and SW. My question is how is it best to impose no-normal flow BCs, $$\vec u \cdot \hat n = 0$$ for any boundary. I found this in the Navier-Stokes example which says that we should impose zero on particular boundaries. I guess that would work but if one had a more complicated geometry I imagine that would have it's problems. bcs = [DirichletBC(Z.sub(0), Constant((1, 0)), (4,)), DirichletBC(Z.sub(0), Constant((0, 0)), (1, 2, 3))] Any suggestions would be greatly appreciated. Cheers, Francis ------------------ Francis Poulin Associate Professor Department of Applied Mathematics University of Waterloo email: fpoulin@uwaterloo.ca Web: https://uwaterloo.ca/poulin-research-group/ Telephone: +1 519 888 4567 x32637