DIFFERENCES IN DYNAMICS OF AN IDEALY EXPANDED MACH 1.3 JET DURING NOISE GENERATION AND RELATIVE QUIET PERIODS
DIFFERENCES IN DYNAMICS OF AN IDEALY EXPANDED MACH 1.3 JET DURING NOISE GENERATION AND RELATIVE QUIET PERIODS
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理想扩展马赫数 1.3 喷气机在噪声产生和相对安静期间的动力学差异
DOI：
10.2514/6.2004-3015
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发表时间：
2004
影响因子：
3.4
通讯作者：
M. Samimy
中科院分区：
文献类型：
--
作者：
J. Hileman;E. Caraballo;B. Thurow;M. Samimy
本文研究了高雷诺数、理想膨胀的1.3马赫射流在强声辐射产生时期和缺乏这种声辐射的较长相对安静时期内大尺度湍流结构的动力学。这些结果是通过一个独特的实验获得的，该实验利用三维传声器阵列估计了大振幅声波的来源，并在两个正交平面上同时显示了流场。其中一架飞机的图像是以167千赫的频率拍摄的。采用适当的正交分解（POD）来创建两个平面内大型结构的尺寸和分布的基础。然后使用这些POD模态来客观地确定噪声产生期间和无明显噪声产生期间射流结构的差异。结果表明，相对安静工况期间的流动以由较大湍流结构组成的低阶POD模态为主，而在噪声产生期间则以捕获大型结构的动态相互作用的高阶POD模态为主。在噪声发射时刻之前的大约一个对流时间尺度内，混合层内形成一系列大尺度结构并解体，在此过程中，大量的环境流体被带入射流核心。这些结果首次显示了大尺度湍流结构的动态相互作用如何在高雷诺数射流中产生声辐射。
The dynamics of large-scale turbulence structures within a high Reynolds number, ideally expanded Mach 1.3 jet were investigated during both the periods of production of strong acoustic radiation and extended periods of relative quiet that lacked such acoustic radiation. These results were acquired through a unique experiment where the sources of large amplitude sound waves were estimated with a three-dimensional microphone array and the flow field was simultaneously visualized on two orthogonal planes. The images from one of the planes were taken at a 167 kHz rate. Proper Orthogonal Decomposition (POD) was employed to create a basis of the size and distribution of large-scale structures within the two planes. These POD modes were then used to objectively determine the differences in the jet structure during noise generation and periods lacking significant noise generation. The results show that the flow during the periods of relative quiet cases is dominated by the lower order POD modes that consist of relatively large turbulence structures while it is dominated by higher order POD modes that capture the dynamic interplay of the large-scale structures during noise generation periods. For approximately one convective time scale prior to the moment of noise emission, a series of large-scale structures forms and disintegrates within the mixing layer and in the process a large amount of ambient fluid is entrained into the core of the jet. For the first time, these results show how the dynamic interplay of large-scale turbulence structures generates acoustic radiation within a high Reynolds number jet.