Computational Analysis of Characteristics of Mach Wave Sources in Supersonic Free-jets
Computational Analysis of Characteristics of Mach Wave Sources in Supersonic Free-jets
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DOI：
10.2514/6.2009-16
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发表时间：
2009-01
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影响因子：
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通讯作者：
T. Nonomura;K. Fujii
中科院分区：
文献类型：
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作者：
T. Nonomura;K. Fujii
为了预报火箭羽流中的声波，采用高分辨率格式研究了马赫波的声源特性。对M=2.0冷喷流、M=3.0冷喷流、M=2.0热喷流和M=3.0热喷流四种理想膨胀超音速射流进行了计算和分析。在计算方面，流体分析采用七阶加权紧致非线性格式，近场声学传播采用十阶紧致格式。用聚焦阵列法和震源可视化方法研究了震源位置。聚焦阵列方法的结果表明，高频源位于上游区域，而低频源位于下游区域。此外，高频源发出的马赫波与轴线成大角度传播，而低频源发出的马赫波与轴成小角度传播。马赫波源位于流体速度高于环境声速的环境超音速区域。利用震源的可视化获得了几乎相同的特征。然后研究了源频率的归一化问题。利用剪切层厚度和轴向速度可以很好地归一化各种超音速喷流的源频率，而不受温度的影响。最后，我们的计算结果表明，马赫波的最低频率由周围超音速区域长度和势核长度决定。
For the prediction of acoustic waves from a rocket plume, source characteristics of Mach waves are investigated with using high resolution schemes. Four ideally-expanded supersonic jets, M=2.0 cold jet, M=3.0 cold jet, M=2.0 hot jet and M=3.0 hot jet, are computed and analyzed. With regard to computation, the seventh order weighted compact non-linear scheme and the tenth order compact scheme are used for the fluid analysis and near fields acoustics propagation, respectively. Source positions are investigated with the focused array method and the visualization of sources. The results of the focused array methods show that the high frequency sources are located at the upstream region, while the low frequency sources are located at the downstream region. In addition, Mach waves emitted from the high frequency sources are propagated with the large angle to the axis, while that from the low frequency sources are propagated with the small angle. Mach wave sources are located in the ambient supersonic region, in which fluid-velocity is higher than the sound speed of the ambient. The almost same features are obtained with using the visualization of sources. Then the normalization of the source frequency is investigated. Using the shear layer thickness and the velocity at the axis, we can normalize the source frequency of various supersonic jets well without the temperature effects. Finally our computational results show that the lowest frequency of Mach waves is determined by the ambient supersonic region length and the potential core length.