The flow around the DTMB5415 surface combatant hull with and without bilge keels is studied numerically by the use of a Large Eddy Simulation (LES) method. The main purpose for bilge keels is to reduce roll motions when operating in ocean waves. The flow resistance should at the same time be affected as little as possible. The computations presented here are for straight course in calm water conditions and show only a small change in the wake of the hull and there by a minimal effect on the resistance. The computations are made as a preparatory step before investigating other conditions, such as yaw angle.