Investigation of cavitation-induced noise on ship propeller.

Controlling and downscaling noise caused by ship's propellers plays significant role on the performance of underwater acoustic systems, and the comfort of the crew and passengers of cruise ships while onboard. The noise produced by propellers exploited by underwater acoustics for detection which critically affects ship's survivability for military purposes. Studies about ships' acoustics present that the most significant source of noise is the noise caused by ships' propellers. One of the most significant sources for propeller noise is cavitation which is a fluid mechanics phenomenon and can be occurred while cruising. It's well known that the sheet type cavitation is the most frequent one that encountered on ship's propellers. The non-uniform fluid flow around propellers and the unsteady behavior of a potential sheet cavitation according to time, lead especially underwater noise and vibration at shaft line and at the ship's hull. For this reason, preventing undesired aforementioned situations at pre-construction phase is very important while analyzing and designing a propeller. In order to eliminate the noise arisen from ships' propellers due to cavitation, several propeller design and analysis studies have been done including the cavitation phenomenon. Currently and also as previously, aforementioned studies which have been done both quantitatively and experimentally, presented significant progress while the necessity of high speed vessels and the development of the computerized technology exist. In this study, a cavitation-noise prediction method which is one of the quantitative analysis methods for ship's propellers based on the "Lifting Surface" method has been used. A propeller was selected with the specific geometry and the running conditions for the application. By switching some geometrical characteristics (skew and pitch distribution) of propellers, effects on performance, characteristics of the cavitation, and the level of the noise investigated quantitatively. Key words: The effect of propeller noise, cavitation, sheet cavitation.