Numerical investigation of aeroacoustics damping performance of a Helmholtz resonator: Effects of geometry, grazing and bias flow
Numerical investigation of aeroacoustics damping performance of a Helmholtz resonator: Effects of geometry, grazing and bias flow
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DOI：
10.1016/j.ast.2019.01.007
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发表时间：
2019-03
影响因子：
5.6
通讯作者：
Gang Wu;Zhengli Lu;Xiao Xu;Weichen Pan;Weiwei Wu;Jun Li;J. Ci
中科院分区：
文献类型：
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作者：
Gang Wu;Zhengli Lu;Xiao Xu;Weichen Pan;Weiwei Wu;Jun Li;J. Ci
本文用数值方法研究了掠掠流及其几何尺寸对亥姆霍兹谐振器气动声学阻尼性能的影响。切向通过谐振腔颈部的掠流用马赫数表示。它从0到0.1变化。利用COMSOL 5.3软件在频域上求解线性化的Navier-Stokes方程，进行二维数值模拟。由于只存在低马赫数掠流，因此首先通过与现有文献的实验和理论数据进行比较来验证数值模型。得到了很好的一致性。然后利用该模型考察了掠掠流量和谐振腔几何尺寸对传输损耗性能的影响。确定了4个关键参数：1)颈部长度，2)颈部直径，3)空腔体积和4)掠流马赫数。研究发现，当掠流马赫数大于0.07时，增大颈长会导致TL max减小。对于增大的腔体体积V r，发现了同样的观察结果。在掠流存在时，较小的亥姆霍兹谐振腔V r或较短的颈长L n与较大的TL max有关。当存在联合偏放牧流时，进行进一步的研究。相对于掠流，可以从3个不同的方向注入偏置流：1)平行流、2)垂直流和3)逆流流。发现偏置流注入方向导致了5 dB的传输损耗差。由于在腔内产生了反向旋转的涡流，偏置流的平行或反向注入被证明与改进的TL性能有关。最后，随着掠流马赫数的增加，即使存在偏置流，总体上也会导致噪声阻尼效果的恶化。本文的工作对赫姆霍兹谐振器在掠流和偏流条件下的气动声学设计有一定的启发。
In this work, the effects of the grazing flow and its geometric dimensions on the aeroacoustics damping performance of a Helmholtz resonator are numerically evaluated. The grazing flow tangentially passing through the neck of the resonator is characterized by Mach number. And it is varied from 0 to 0.1. 2D numerical simulations are conducted by solving linearized Navier–Stokes equations in frequency domain via COMSOL 5.3. The numerical model is first validated by comparing with experimental and theoretical data available in literature, as a low Mach number grazing flow is present only. Good agreement is obtained. The model is then used to examine the effect of the grazing flow and the resonator geometric dimensions on transmission loss (TL) performance. Four key parameters are identified, and they include 1) the neck length, 2) neck diameter, 3) cavity volume and 4) the grazing flow Mach number. It is found that as the grazing flow Mach number is greater than 0.07, increasing the neck length leads to a decreased TL max. Same observation is found for increased cavity volume V r. Smaller Helmholtz resonator V r or shorter neck length L n is found to be involved with a larger TL max in the presence of the grazing flow. Further study is then conducted, when there is a joint bias–grazing flow. The bias flow could be injected with respect to the grazing flow in 3 different directions, 1) parallel, 2) perpendicular and 3) counter flow. The bias flow injection direction is found to lead to 5 dB transmission loss difference. Parallel or counter injection of the bias flow is showed to be associated with improved TL performance, since there are counter-rotating vortices produced in the cavity. Finally, increasing the Mach number of the grazing flow leads to the noise damping effectiveness being deteriorated in general, even in the presence of a bias flow. The present work shed lights on the aeroacoustics design of Helmholtz resonators in the presence of a grazing and bias flow.