Interaction of second-mode wave packets with an axisymmetric expansion corner
Interaction of second-mode wave packets with an axisymmetric expansion corner
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第二模波包与轴对称扩展角的相互作用
DOI：
10.1007/s00348-021-03235-2
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发表时间：
2021
影响因子：
2.4
通讯作者：
S. Laurence
中科院分区：
文献类型：
--
作者：
C. Butler;S. Laurence
在马赫-6激波风洞中进行了实验，以考察突然膨胀对高超声速边界层不稳定波的影响。测试几何图形由5∘\DocumentClass[12pt]{Minimum}\usepackage{amsath}\usepackage{amsFonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathsfs}\usepackage{upgreek}\setLong{\oddsidemarin}{-69pt}\Begin{Document}$$^{\cic}$$\end{Document}半角度组成，名义上是带有圆柱形延伸的尖锐圆锥体。超高速纹影(550-747 khz\Docentclass[12pt]{minimum}\usepackage{amsath}\usepackage{wa ysym}\usepackage{amsfonts}\usepackage{amsbsy}\usepackage{matrsfs}\usepackage{upgreek}\setlong{oddsidemargin}{-69pt}\{Begin文档}$550-747\，\matrm{khz}$\end{Document})被用作流询问的主要手段，提供了不稳定发展的全局视图；较高的帧率使频谱分析技术能够在整个视域中使用。瞬时纹影图像显示，拐角下游的第二模和湍流扰动都有显著的衰减。这种衰减被发现是宽带的，尽管可以看到低频成分沿着圆柱体放大。采用谱特征正交分解(SPOD)来确定模式内容的空间结构和发展。在圆柱体上发现了与新的低频成分一起生长的频移第二模波。利用SPOD模式对扰动传播速度进行了分析，发现与基于相关的方法有很好的一致性。采用双谱分析方法研究了边界层内的非线性能量交换机制。观察到了第二模基波的显著共振以及拐角上游的低频耦合，尽管非线性的证据在下游消散了。
Experiments were performed in a Mach-6 shock tunnel to examine the impact of an abrupt expansion on hypersonic boundary-layer instability waves. The test geometry consisted of a 5∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document} half-angle, nominally sharp cone with a cylindrical extension. Ultra-high-speed schlieren (550-747kHz\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$550-747\,\mathrm{kHz}$$\end{document}) was employed as the primary means of flow interrogation, providing a global view of instability development; the high frame rate enabled the use of spectral analysis techniques throughout the entire field of view. Instantaneous schlieren images demonstrated significant decay of both second-mode and turbulent disturbances downstream of the corner. This decay was found to be broadband, though low-frequency content was seen to amplify along the cylinder. Spectral proper orthogonal decomposition (SPOD) was implemented to determine the spatial structure and development of the modal content. Frequency-shifted second-mode waves were identified growing on the cylinder alongside the new low-frequency content. Analysis of the disturbance propagation speeds using the SPOD modes was found to give good agreement with a correlation-based approach. Bispectral analysis was employed to examine nonlinear energy exchange mechanisms within the boundary layer. Significant resonance of the second-mode fundamental was observed along with low-frequency coupling upstream of the corner, though evidence of nonlinearity dissipated downstream.