cfx multigrid
 

does anyone now what cfx uses to solve the linear system if you set "solver multigrid = f" (as in switch off multigrid)?

Good question, I am not sure. I assume it disables the grid coarsening stuff which leaves you just with the linear solver. Almost always this will result in much slower convergence, but on rare cases it may help.

i've yet to come across a case where this would help :)

i think you're right, it probably just uses the coarsest-grid-level solver, but i wonder what that would be. can't really be a direct solver, otherwise it would slow down to crawl ...