Applying all pressure BCs and using maximum-strength ingredients (LU,GMRES/10) appears to make PCD work for the pressure-driven SWE.
Adding a mass matrix into the F_p seems to help .. why?
FGMRES is safer.
Can weaken LU for the Schur complement part. Now onto the top-left block ...
Even for Re=30, hypre is OK. But for Re=40, it isn't.
What happens between Re=32 and Re=33? Hypre totally stops working, that's what happens.