I have a multiphysics problem in COMSOL involving the laplace equation, navier stokes equations and heat transfer. When I use the direct solver, it solves fine. When I switch to iterative, I cannot get it to solve. Basically, I will encounter an error saying that inf or NaN encountered in the solver for SOR. I have to use iterative due to the large number of elements (in real case), so direct solver is out of the question.