An overview on the use of the Ffowcs Williams-Hawkings equation for the hydroacoustic analysis of marine propellers

Since the last 70s, the integral formulations solving the Ffowcs Williams-Hawkings equation are the standard approach for the prediction of noise generated by a body moving in a fluid flow and, in particular, propulsion and/or lifting devices based on rotating blades. This methodology represents the base of research and commercial software used by aeronautical industry and is more and more being applied to naval sector too, in the attempt of providing the shipbilding industry with effective predictive tools, which to fulfill the stringent regulations on underwater noise emission with. The paper offers a brief overview on the use of the Acoustic Analogy for marine propeller hydroacoustics. At first, we propose a comprehensive numerical analysis which emphasizes the intrisinc, nonlinear nature of the problem. Then, some possible computational strategies to evaluate the noise induced by a sheet cavitation phenomenon are proposed and compared. Some numerical results are presented, by avoiding as much as possible any mathematical detail on the adopted, integral formulations and focusing the attention of the significant capabilities and the effectiveness of the methodology.