Blade number effect upon high-frequency marine propulsor noise: model test data

Abstract

Object and purpose of research. This paper discusses blade systems of propellers and water jets. The purpose of the study was to outline the ways to mitigation of high-frequency non-cavitation noise of marine propulsors. Subject matter and methods. The study analyses Russian and foreign publications on aero- and hydroacoustics of propellers and foil systems. It also determines the parameters of turbulent boundary layer on propeller blades with respect to its effect upon propeller noise radiation. Noise assessment methods obtained for aerodynamics of foil systems have been applied to marine propulsors. Main results. Theoretical studies have shown that marine propellers with fewer blades tend to have lower radiation of high-frequency noise. Direct noise measurements of propulsor models performed under this study have confirmed this trend. Conclusion. In contrast to the low-frequency propeller noise, high-frequency acoustic radiation can be achieved through reduction of propeller blade number.