EXPERIMENTS ON THE FLOW AND ACOUSTIC PROPERTIES OF A MODERATE-REYNOLDS-NUMBER SUPERSONIC JET
EXPERIMENTS ON THE FLOW AND ACOUSTIC PROPERTIES OF A MODERATE-REYNOLDS-NUMBER SUPERSONIC JET
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DOI：
10.1017/s0022112082000408
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发表时间：
1982-01-01
影响因子：
3.7
通讯作者：
MCLAUGHLIN, DK
中科院分区：
文献类型：
--
作者：
TROUTT, TR;MCLAUGHLIN, DK
本文对中等雷诺数（Re = 70000）、马赫数M = 2·1的轴对称射流的流动和声学特性进行了实验研究。这些测量扩展了以前在本实验室进行的实验研究，以更高的雷诺数制度的流动和声学过程是相当复杂的。事实上，这种射流的平均流动和声学特性被确定为与已发表的高雷诺数射流的特性密切相关。流场测量的主要结果表明，射流剪切环在很宽的频率范围内是不稳定的。这些不稳定性的初始增长率和波长测量的热线被认为是在合理的协议与线性稳定性理论的预测。此外，与亚音速喷流的结果一致，喷流的潜在核心被发现是最敏感的激励频率附近的斯特劳哈尔数S = 0·3。S = 0·2附近有组织扰动的总体发展似乎与使用最初由Morris和Tam开发的不稳定性理论进行的计算基本一致。声学近场的特征在于自然和激发（纯音）射流的声压级和方向性。此外，还测量了主要光谱分量的传播方向和方位角特性。确定了大尺度流动扰动以与射流轴线成30°为中心的定向模式辐射噪声。从简单的射线追踪看来，这些扰动产生的噪声主要产生在射流区域附近，在该区域相干波动的振幅饱和并开始衰减。还确定近场声音的大尺度分量主要由轴对称（n = 0）和螺旋（n = ±1）模式组成。占主导地位的噪声产生机制似乎是一个组合的马赫波的产生和与大尺度不稳定的饱和和解体的过程。最后，不稳定型噪声产生模型的进一步发展似乎有相当大的希望。
An experimental investigation of the flow and acoustic properties of a moderate-Reynolds-number (Re = 70000), Mach number M = 2·1, axisymmetric jet has been performed. These measurements extended the experimental studies conducted previously in this laboratory to a higher-Reynolds-number regime where the flow and acoustic processes are considerably more complex. In fact, mean-flow and acoustic properties of this jet were determined to be closely comparable to published properties of high-Reynolds-number jets.The major results of the flow-field measurements demonstrate that the jet shear annulus is unstable over a broad frequency range. The initial growth rates and wavelengths of these instabilities as measured by a hot wire were found to be in reasonable agreement with linear stability theory predictions. Also, in agreement with subsonic-jet results, the potential core of the jet was found to be most responsive to excitation at frequencies near a Strouhal number of S = 0·3. The overall development of organized disturbances around S = 0·2 seems to agree in general with calculations performed using the instability theory originally developed by Morris and Tam.The acoustic near field was characterized in terms of sound-pressure level and directivity for both natural and excited (pure-tone) jets. In addition, propagation direction and azimuthal character of dominant spectral components were also measured. It was determined that the large-scale flow disturbances radiate noise in a directional pattern centred about 30° from the jet axis. The noise from these disturbances appears from simple ray tracing to be generated primarily near the region of the jet where the coherent fluctuations saturate in amplitude and begin to decay. It was also determined that the large-scale components of the near-field sound are made up predominately of axisymmetric (n = 0) and helical (n = ±1) modes. The dominant noise-generation mechanism appears to be a combination of Mach-wave generation and a process associated with the saturation and disintegration of the large-scale instability. Finally, the further development of a noise-generation model of the instability type appears to hold considerable promise.