Propeller design by optimisation for underwater radiated noise reduction: a full scale application

In the last years, an increasing attention has been devoted to ships Underwater Radiated Noise (URN), with the progressive introduction of noise reduction Guidelines by international organizations such as IMO, Classification Societies voluntary notations, limits and incentives in specific areas. In this context, a large effort has been spent in the study of cavitating propeller noise since it represents the dominating noise source on ships. Over the years, the University of Genoa has developed strategies for propeller design by optimisation aimed to the reduction of cavitation and noise as a side effect, limiting possible negative consequences on the propulsion efficiency. In the context of the EU-funded LIFE-PIAQUO project it was possible to perform a complete optimisation activity, starting from a real test case (a small passenger boat operating in Mediterranean marine protected areas) and retrofitting the propellers for dedicated sea trials. The present paper reports the main results of these activities, highlighting the capability of the proposed methods, through a comparative full-scale validation of the outcomes of the design activity.