Mimani A, Prime Z, Moreau D J, Doolan C J
School of Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia.
School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia.
J Acoust Soc Am. 2016 Feb;139(2):740-63. doi: 10.1121/1.4941564.
This paper presents an experimental application of the aeroacoustic time-reversal (TR) source localization technique for studying flow-induced noise problems and compares the TR results with those obtained using conventional beamforming (CB). Experiments were conducted in an anechoic wind tunnel for the benchmark test-case of a full-span circular cylinder located in subsonic cross-flow wherein the far-field acoustic pressure was sampled using two line arrays (LAs) of microphones located above and below the cylinder. The source map obtained using the signals recorded at the two LAs without modeling the reflective surfaces of the contraction-outlet and cylinder during TR simulations revealed the lift-dipole nature of aeroacoustic source generated at the Aeolian tone; however, it indicates an error of 3/20 of Aeolian tone wavelength in the predicted location. Modeling the reflective contraction-outlet during TR was shown to improve the focal-resolution of the source and reduce side-lobe levels, especially in the low-frequency range. The experimental TR results were shown to be comparable to (a) the simulation results of an idealized dipole at the cylinder location in wind-tunnel flow and (b) that obtained by monopole and dipole CB, thereby demonstrating the suitability of TR method as a diagnostic tool to analyze flow-induced noise generation mechanism.
本文介绍了用于研究流动诱导噪声问题的气动声学时间反转（TR）源定位技术的实验应用，并将TR结果与使用传统波束形成（CB）获得的结果进行了比较。实验在消声风洞中进行，针对位于亚音速横流中的全跨圆柱体的基准测试案例，其中远场声压使用位于圆柱体上方和下方的两个线性麦克风阵列（LA）进行采样。在TR模拟过程中，在未对收缩出口和圆柱体的反射表面进行建模的情况下，使用在两个LA处记录的信号获得的源图揭示了在埃奥利安音调下产生的气动声源的升力偶极性质；然而，它表明预测位置存在埃奥利安音调波长3/20的误差。结果表明，在TR过程中对反射收缩出口进行建模可提高源的聚焦分辨率并降低旁瓣水平，尤其是在低频范围内。实验TR结果被证明与（a）风洞流动中圆柱体位置处理想化偶极子的模拟结果以及（b）通过单极子和偶极子CB获得的结果相当，从而证明了TR方法作为分析流动诱导噪声产生机制的诊断工具的适用性。
