Effect of wavy leading edge on hydrofoil-turbulence interaction noise

波状前缘对水翼湍流干涉噪声的影响

¹ School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China
² Key Laboratory of Unmanned Underwater Vehicle Technology, Northwestern Polytechnical University, Xi'an 710072, China

Received: 15 March 2021

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.

摘要

为解决水下噪声污染问题以及提升水下航行器声隐身性能，根据座头鲸鳍肢前缘结节结构对NACA0020进行波状前缘改型设计。采用大涡模拟和FW-H方程相结合的方法，对改型前后翼型的湍流干涉流场及噪声特性进行了研究。结果表明波状前缘能够有效降低翼型的湍流干涉噪声，尤其是高于89.55 Hz的宽频噪声。波状前缘翼型的总声压级指向性特征与原翼型相同，均呈偶极子特性，但其各个方向上的噪声值均有一定降低。对总声压级进行分频段计算发现波状前缘在1 000~5 000 Hz的中高频段内降噪最好，降噪量可达12.6 dB。通过流场分析得出波状前缘的降噪作用主要与前缘压力脉动降低和展向流动增强导致涡在展向的相干性减弱有关。