Acoustic Radiation From a Mach 14 Turbulent Boundary Layer
Acoustic Radiation From a Mach 14 Turbulent Boundary Layer
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来自 14 马赫湍流边界层的声辐射
DOI：
10.2514/6.2016-0048
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Meelan Choudhari
中科院分区：
文献类型：
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作者：
Chao Zhang;L. Duan;Meelan Choudhari
采用直接数值模拟（DNS）研究了名义自由流马赫数为14、壁面温度为0:18恢复温度的高速湍流边界层所产生的湍流统计和辐射场。流动条件落在阿诺德工程开发中心（AEDC）超高速隧道9号设施喷管出口条件范围内。流向区域尺寸约为进口边界层厚度的200倍，有效雷诺数范围为Re 450 ~ 650。与以往对高马赫数湍流边界层的研究一致，在这种流动条件下，湍流边界层的弱可压缩性假设仍然适用，计算结果证实了van Driest变换和Morkovin标度的有效性。雷诺兹类比在地表是有效的；表面压力、壁面剪应力和热流密度波动的均方根分别为表面平均值的24%、53%和67%。发现压力波动的幅度和主导频率在内层（z/ δ 0）内变化很大。<或近似。0.08或z+ <或近似。50)。压力波动的预乘频谱峰值为f(δ)/U（次无穷）近似。并移至频率较低的f(δ)/U（次无穷）附近。0.7在自由流中，压力信号主要是声学信号。在壁面和自由流中，压力谱的主导频率与自由流马赫数有显著的相关性。
Direct numerical simulations (DNS) are used to examine the turbulence statistics and the radiation field generated by a high-speed turbulent boundary layer with a nominal freestream Mach number of 14 and wall temperature of 0:18 times the recovery temperature. The flow conditions fall within the range of nozzle exit conditions of the Arnold Engineering Development Center (AEDC) Hypervelocity Tunnel No. 9 facility. The streamwise domain size is approximately 200 times the boundary-layer thickness at the inlet, with a useful range of Reynolds number corresponding to Re 450 650. Consistent with previous studies of turbulent boundary layer at high Mach numbers, the weak compressibility hypothesis for turbulent boundary layers remains applicable under this flow condition and the computational results confirm the validity of both the van Driest transformation and Morkovin's scaling. The Reynolds analogy is valid at the surface; the RMS of fluctuations in the surface pressure, wall shear stress, and heat flux is 24%, 53%, and 67% of the surface mean, respectively. The magnitude and dominant frequency of pressure fluctuations are found to vary dramatically within the inner layer (z/delta 0.< or approx. 0.08 or z+ < or approx. 50). The peak of the pre-multiplied frequency spectrum of the pressure fluctuation is f(delta)/U(sub infinity) approx. 2.1 at the surface and shifts to a lower frequency of f(delta)/U(sub infinity) approx. 0.7 in the free stream where the pressure signal is predominantly acoustic. The dominant frequency of the pressure spectrum shows a significant dependence on the freestream Mach number both at the wall and in the free stream.