Large Eddy Simulation of Conventional and Bias Flow Acoustic Liners
Large Eddy Simulation of Conventional and Bias Flow Acoustic Liners
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常规和偏流声学衬垫的大涡模拟
DOI：
10.1115/gt2017-63693
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Yuzo Inokuchi and Tatsuya Ishii
中科院分区：
文献类型：
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作者：
Soufiane Ramdani;Nobuhiko Yamasaki;Yuzo Inokuchi and Tatsuya Ishii
本文通过数值求解可压缩Navier-Stokes方程，研究了声衬的声学特性和穿孔板周围的流场。为了更好地理解内衬的声学特性，数值模拟很难可视化板上小孔周围的流动。Tam等人[1]先前通过实验和直接数值模拟对常规声学内衬在法向声波入射下的情况进行了研究。Tam等人[1]获得的结果用于验证本研究中获得的结果。此外，本文还采用大涡模拟方法对偏流对缝隙衬层吸声性能的影响进行了数值模拟，在计算气动声学（CAA）中采用了两种不同的方法来计算缝隙衬层的吸声系数。第一种方法是传递函数法，它模拟了实验中所用的阻抗声管。第二种方法是粘性耗散法，它计算了声能在粘性耗散中转化的功率，在声源声压级为150 dB时，粘性耗散法计算的吸声系数与理论值吻合较好。在这种情况下，脱落涡的发展，并被认为是声音耗散的主要原因。传递函数和粘性耗散的方法来计算的吸收系数给出了良好的结果，频率更高，等于2 kHz时，声源声压级设置为130 dB。仅在1 kHz的频率下，获得的值与Tam等人[1]获得的值不同。当谐振器仅在130 dB的法向声波入射下时，未观察到脱落涡流。研究了通过谐振器孔径的偏流的引入。在这种情况下，衬里的声学性能和在孔处的流动行为与传统衬里的比较是突出的。当声压级等于130 dB时，当引入穿过孔的偏流时，对于高于谐振频率的频率获得吸收的增加。另一方面，对于谐振频率，吸收减少。然而，当SPL等于150 dB时，在谐振频率附近吸收系数较高，而对于较高频率，吸收系数较低。
This study deals with the acoustic behavior of acoustic liners and the flow field around the perforated plate by solving numerically the compressible Navier-Stokes equations. The difficulty of visualizing the flow around the small holes of the plate makes the numerical simulations very attractive in order to well understand the acoustic behavior of the liner.The chosen liner was previously studied by Tam et al. [1] experimentally and using the Direct Numerical Simulation for the case of a conventional acoustic liner under normal sound wave incidence. The results obtained by Tam et al. [1] serve for the validation of the results obtained in the present research. Moreover, in this study, the focus is on the numerical simulation of the influence of bias flow on the absorption performance of a slit liner using the large eddy simulation.Two different methods are used to calculate the absorption coefficient in the computational aeroacoustics (CAA) simulation of the resonator. The first method is the transfer function method, and it simulates the impedance acoustic tube used in the experiment. The second method is the viscous dissipation method, and it calculates the power at which the acoustic energy is converted in viscous dissipation.The viscous dissipation method gives good agreement for the calculated absorption coefficients at the sound source pressure level of 150 dB. Shed vortices are developed in this case, and are considered to be the main cause of sound dissipation.The transfer function and the viscous dissipation methods used to calculate the absorption coefficients give good results for frequencies higher and equal to 2 kHz when the sound source pressure level is set to 130 dB. Only at the frequencies of 1 kHz, the obtained values are different from the values obtained by Tam et al. [1]. Shed vortices are not observed when the resonator is under only normal sound wave incidence of 130 dB.The introduction of a bias flow passing through the aperture of the resonator is investigated. The acoustic performance of the liner in this case and a comparison of the flow behavior at the aperture with a conventional liner is highlighted. When the sound pressure level is equal to 130 dB, an increase in the absorption is obtained for frequencies above the resonance frequency when the bias flow passing through the aperture is introduced. On the other hand, the absorption is reduced for the resonance frequency. However, when the SPL is equal to 150 dB, the absorption coefficient is higher near the resonance frequency, while for higher frequencies the absorption coefficient is lower.