Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China.
J Acoust Soc Am. 2013 Feb;133(2):697-708. doi: 10.1121/1.4773351.
This paper reports a numerical study of the aeroacoustics of merging flow at T-junction. The primary focus is to elucidate the acoustic generation by the flow unsteadiness. The study is conducted by performing direct aeroacoustic simulation approach, which solves the unsteady compressible Navier-Stokes equations and the perfect gas equation of state simultaneously using the conservation element and solution element method. For practical flows, the Reynolds number based on duct width is usually quite high (>10(5)). In order to properly account for the effects of flow turbulence, a large eddy simulation methodology together with a wall modeling derived from the classical logarithm wall law is adopted. The numerical simulations are performed in two dimensions and the acoustic generation physics at different ratios of side-branch to main duct flow velocities VR (=0.5,0.67,1.0,2.0) are studied. Both the levels of unsteady interactions of merging flow structures and the efficiency of acoustic generation are observed to increase with VR. Based on Curle's analogy, the major acoustic source is found to be the fluctuating wall pressure induced by the flow unsteadiness occurred in the downstream branch. A scaling between the wall fluctuating force and the efficiency of the acoustic generation is also derived.
本文报道了 T 型分叉处汇流流动的空气声学数值研究。主要重点是阐明流动非稳定性产生的声学。该研究通过执行直接空气声学模拟方法进行，该方法使用守恒元和求解元方法同时求解非定常可压缩纳维-斯托克斯方程和理想气体状态方程。对于实际流动，基于管道宽度的雷诺数通常相当高（>10^5）。为了正确考虑流动湍流的影响，采用了大涡模拟方法以及源自经典对数壁定律的壁面模型。数值模拟在二维进行，研究了不同支管路与主管道流速比 VR（=0.5、0.67、1.0、2.0）的汇流流动结构的非定常相互作用水平和声学产生效率。结果表明，随着 VR 的增加，汇流流动结构的非定常相互作用水平和声学产生效率都增加。根据 Curle 的类比，发现主要声源是下游分支中流动非稳定性引起的壁面脉动压力。还推导了壁面脉动力与声学产生效率之间的标度关系。
