Optimization based design of high speed craft propellers

The state of the art of fast propeller design codes is mainly based on classical vortical theories by Lerbs. Their crude simplifications make them often insufficiently accurate in the case of modern fast propellers geometries having highly skewed blades, non-conventional profiles, mixed type of cavitation and strict constraints about pressure pulses and radiated noise. Advanced design tools, based on (more) accurate flow solvers able to deal with the multi-objective nature of any modern design are, definitely, required. In light of this, the design of a propeller for a high-speed craft is addressed by using a multi-objective numerical optimization approach, based on a fast and reliable BEM, a parametric description of the geometry and a genetic algorithm. The new propeller is designed to improve the propulsive efficiency, reduce the cavitation extension, increase the inception speed and simultaneously maximize the ship speed. A final geometry is selected to verify the reliability of the design procedure by means of dedicated RANSE analyses, cavitation tunnel tests and full-scale measurements on a high-speed craft provided by Azimut|Benetti.