Effect of wavy leading edge on hydrofoil-turbulence interaction noise

Abstract

In order to solve the underwater noise pollution and improve the acoustic stealth performance of underwater vehicles, NACA0020 was bionically modified according to the structure of the leading edge tubercles of humpback fin. The flow field and noise characteristics of the hydrofoil-turbulent interaction model before and after the modification were studied by using the large eddy simulation and the FW-H equation. The results show that the wavy leading edge can effectively reduce the turbulence interaction noise of the hydrofoil, especially the broadband noise after 89.55 Hz. The overall sound pressure level(OASPL) directivity of the wavy leading edge hydrofoil are the same as the original hydrofoil, and both have dipole characteristics, but the noise value in all directions is reduced to a certain extent. The OASPL is calculated and analyzed in different frequency bands. The results show that the OASPL has a best reduction in 1 000-5 000 Hz frequency band, and the noise can be reduced up to 12.6 dB. Through the analysis of flow field, it is concluded that the noise reduction effect of wavy leading edge mainly relates to the decrease in pressure fluctuation at leading edge and the decrease in coherence of vortex in spanwise direction caused by the enhancement of spanwise flow.