HELP! Simulate flow pattern of stirring reactions.
 

Recently, I'm doing a research on the Metal Matric Composites fabrication method. One of the fabrication method is Stir Casting, and it involves just a very simple model of a stirrer or an impeller (a thin rectangular shape impeller) in a simple cylidrical shape vessel. What I did is, first of all, create the mesh file in Gambit, and set the stirrer/impeller as moving wall(rotational moving wall) by using the k-epsilon model. My question is, whether i can use k-epsilon model or others? something like Spalart-allmaras? will it gives me better result? how can i be sure whether my fluid is in turbulent or laminar? To those who know the answer, please reply as soon as possible, tell me the steps that I must follow to complete my simulation.