Preconditioning and fast solvers for incompressible flow

−ν∇u+ u.∇u+∇p = f ∇ · u = 0 which are taken to hold in some domain Ω ⊂ IR together with appropriate boundary conditions. We concentrate on the steady state equations; timedependent problems are essentially easier in the context of iterative methods. We will make some comment on this later. The numerical results we present here come from mixed finite element approximation though the techniques are not restricted by approximation method. Whichever approximation techinique is employed the discrete equations arise in the form [ F (u) B B 0 ] [ u p ]