A systematic experimental approach to cavitation noise prediction of marine propellers

Abstract

Minimization of propeller cavitation noise is best achieved through accurate and reliable pre-dictions at an early design stage. The effect of cavitation and particularly the dynamics of cav-itation on URN is rather complex to understand and the current state of the art does not offer a plausible cavitation noise prediction method which can be implemented within the propeller design spiral. Within this framework, the aim of the present thesis is to enhance the understand-ing of the propeller cavitation noise by conducting detailed systematic cavitation tunnel tests to investigate the main propeller design parameters and operating conditions and to scrutinize their impact on propeller Radiated Noise Levels (RNL). The resulting experimental data are also utilized to compile a database that enables engineering a novel noise prediction method to be developed and used at preliminary design stage, using standard series approach. A holistic approach to cavitation noise has been adopted through experimental investigations into oblique flow effects on propeller noise and by conducting full scale and model scale noise experiments of a research vessel. These have been used to evaluate the capabilities of the adopted standard series based experimental prediction methodology. The accumulated knowledge based on prior experiments has been utilized to design standard series propeller test campaign. Experiments using members of Meridian standard propeller se-ries were tested both in an open water condition and also behind systematically varied wake inflows. Initially, a small subset of the Meridian standard propeller series was chosen, with loading conditions derived from in-service, ocean-going vessels. The resulting measured noise data were extrapolated to full-scale based on the powering information of these vessels to com-pare with average shipping noise data. Finally, a larger subset of the propeller series was tested systematically to compile a database of propeller cavitation noise and for the development of noise prediction software.