Numerical Study of Non-Cavitating Underwater Propeller Noise

Abstract

Non-cavitating noise of underwater propeller is numerically investigated. The main purpose is to analyze non-cavitating noise in various operating conditions with different configurations. The noise is predicted using time-domain acoustic analogy and boundary element method. The flow field is analyzed with potential based panel method, and then the time-dependent pressure data are used as the input for Ffowcs-Williams Hawkings formulation to predict the far-field acoustics. Boundary element method is also considered to investigate the effect of ducted propellers. Sound deflection and scattering effect on the duct is considered with the BEM. The governing equations are based on the assumption that all acoustic pressure is linear. A scattering approach is applied in which the acoustic pressure field is split into the known incident component and the unknown scattered component. Noise prediction results are presented for single propeller and ducted propeller in non-uniform flow conditions. The investigation reveals that the effect of a duct on the acoustic performance of propellers is small in the far field under non-cavitating situations since the noise directivities of single and ducted propeller are almost the same. Only the high order BPFs are influenced by the existence of the duct.