Numerical prediction of tonal noise for non-cavitating propellers in effective wake

Abstract

ABSTRACTThe tonal noise prediction of non-cavitating seven-bladed propellers in effective wake are conducted based on Farassat's formulation 1A in this article. First, the noise characteristics of a seven-bladed propeller in nominal and effective wakes are predicted and compared with each other. Then, the effects of blade skew and rake distributions on the noise characteristics are analysed for two groups of propellers. The results indicate that the acoustic pressure due to blade thickness is negligible. The tonal noise occurs at the blade passage frequency (BPF) and its multiples. The maximum sound pressure level (SPL) at BPF in the nominal wake is 3 dB higher than that in the effective wake. As the skew angle increases, the maximum SPL and acoustic energy at BPF decreases and the direction of the maximum SPL becomes closer to the propeller plane. The rake has little influence on the SPL and acoustic energy.