Numerical simulation of the cavitating noise of contra-rotating propellers based on detached eddy simulation and the Ffowcs Williams–Hawkings acoustics equation

Abstract

Contra-rotating propellers (CRPs) are widely used in different kinds of underwater vessels, owing to their excellent stability, propulsive efficiency, and balanced torque distribution characteristics. However, the cavitation that occurs due to their high rotational speeds also generates high levels of cavitation noise. In this study, CRP noise radiations were predicted via detached-eddy simulations with the shear stress transfer k-ω turbulence model, the Ffowcs Williams–Hawkings (FW–H) acoustics model, and the Schnerr–Sauer cavitation model. The cavitation noise of the CRP was predicted using sound radiation theory for spherical bubbles and compared to non-cavitation noise levels from the FW–H equation. It was found that the non-cavitation noise of the CRP is significantly louder in the axial direction than in the radial direction. Furthermore, the noise sound-pressure levels (SPLs) of the flow field generally decrease with increasing frequency. When the effects of cavitation on the flow are taken into account, the SPLs of the CRP noise become significantly higher at all equidistant positions from the center of the propeller. The anisotropy in sound pressure also becomes insignificant when cavitation is present.