Large Eddy Simulation of a Near Sonic Turbulent Jet and Its Radiated Noise
Large Eddy Simulation of a Near Sonic Turbulent Jet and Its Radiated Noise
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DOI：
10.2514/6.2001-376
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
G. Constantinescu;S. Lele
中科院分区：
文献类型：
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作者：
G. Constantinescu;S. Lele
本文采用数值模拟的方法，对雷诺数分别为3,600和72,000的高速近音速(Ma=0.9)可压缩射流的湍流动力学和声场进行了同步计算。采用大涡模拟与精确数值格式相结合的方法，对射流近场的非定常流动和声场进行了数值模拟。计算结果表明，射流平均参数、平均速度场和湍流统计特性与实验数据和其它数值模拟结果吻合较好。近场的声音是从模拟中直接计算出来的。计算结果表明，在Strouhal数ST=0.25-0.3附近，能捕捉到膨胀谱和压力谱的峰值，这与实验测量的典型喷流噪声谱是一致的。近场的膨胀等值线显示了形成的声波，其优势波长为3.2-4喷流直径，对应于膨胀谱中的峰值。正如预期的那样，非紧凑噪声源被发现在与潜在核心端相对应的区域中最占优势。大涡模拟对辐射噪声的贡献较小，不会污染声场中的杂散高频噪声。然而，声音的频谱显示出远离峰值频率的快速衰减。这是由于在潜在的核关闭之前该区域的剪切层处于准层流状态，以及在观测位置方位角分辨率不足的可能影响。需要进一步分析大涡模拟的效果，特别是在高频情况下。
In this paper numerical simulations are used to calculate the turbulence dynamics simultaneously with the sound field for a high-speed near-sonic (Ma=0.9) compressible jet at two Reynolds numbers of 3,600 and 72,000. LES (Large Eddy Simulation) in conjunction with accurate numerical schemes is used to calculate the unsteady flow and sound in the near field of the jet. It is shown that the jet mean parameters, mean velocity fields and turbulence statistics are in good agreement with experimental data and results from other simulations. The sound in the near-field is calculated directly from the simulations. The calculations are shown to capture the peak in the dilatation and pressure spectra around a Strouhal number St=0.25-0.3, in agreement with typical jet-noise spectra measured in experiments. Dilatation contours in the near-field show the formation of acoustic waves with a dominant wavelength of 3.2-4 jet diameters, corresponding to the peak in the dilatation spectra. As expected, the non-compact noise sources are found to be most dominant in the region corresponding to the end of the potential core. The contribution of the LES model to the radiated noise appears to be weak and does not contaminate the sound field with spurious high-frequency noise. However, the frequency spectra of the sound show a rapid falloff away from the peak frequency. This is attributed to the quasi-laminar state of the shear-layers in the region prior to potential core closure, and a possible effect of insufficient azimuthal resolution at the observed location. Further analysis of the effect of the LES model, especially at high frequencies, is needed.