santiagomarquezd 
March 2, 2013 10:49 
Hi, the momentum predictor is a first approximation of the velocity field obtained from the solution of a momentum equation assembled with the previous timestep pressure field. This velocity doesn't fulfill the restriction given by the continuity equation which is achieved laterly by the PISO method. Sometimes you can avoid the solution of the momPred saving time, but it can lead to a bad convergence in the PISO loop. Is a user's choice based in the problem behavior.
Regards.
