Zhang Xiaoqi, Cheng Li
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China.
J Acoust Soc Am. 2019 Apr;145(4):2461. doi: 10.1121/1.5098785.
Micro-perforated panels (MPPs) are widely used for broadband sound absorptions. For a MPP exposed to a grazing flow, existing acoustic impedance formulas based on different flow parameters give inconsistent results, thus calling for a systematic investigation of the issue to find more intrinsic flow parameters allowing for a reliable acoustic impedance prediction. In this study, three-dimensional CFD simulations are conducted on a MPP hole with a backing space in a flow duct. Numerical results allow identifying the flow velocity gradient in the viscous sublayer as the intrinsic flow parameter and show its linear relationship with a flow-related term in the acoustic resistance formula. Through a linear regression analysis, an acoustic resistance formula is established within a certain flow range (Mach number up to 0.25) under the linear acoustic regime. The validity of the impedance formula is demonstrated through comparisons with existing results and experimental data reported in the literature, showing good agreement and superiority in terms of the prediction accuracy.
微穿孔板（MPP）广泛用于宽带吸声。对于暴露在掠流中的MPP，基于不同流动参数的现有声阻抗公式给出的结果不一致，因此需要对该问题进行系统研究，以找到更多能实现可靠声阻抗预测的内在流动参数。在本研究中，对流动管道中带有背衬空间的MPP孔进行了三维计算流体力学（CFD）模拟。数值结果表明，粘性亚层中的流速梯度是内在流动参数，并显示出它与声阻公式中与流动相关项的线性关系。通过线性回归分析，在一定流动范围内（马赫数高达0.25）的线性声学 regime 下建立了声阻公式。通过与文献中报道的现有结果和实验数据进行比较，证明了阻抗公式的有效性，在预测精度方面显示出良好的一致性和优越性。
