标题： 基于网络理论的高速边界层Mack模态不稳定性表征方法 显示英文标题

标题： A network-theoretic approach for characterizing Mack-mode instability in high-speed boundary layers

摘要： 在这里，我们提出一种基于网络理论的方法，研究在马赫6的层流边界层流过$7^\circ$锥体的高速阴影图数据中发现的Mack模不稳定性特征。 这些数据包含以相干绳状结构形式存在的不稳定性波包，这些结构表现出间歇性。 间歇性意味着传统的傅里叶技术并不特别适合分析。 网络分析，这在处理各种复杂系统中的偶发时空数据方面是众所周知的，提供了一个替代且更合适的框架。 应用了时变空间邻近网络的技术到当前数据中。 网络拓扑中的连通组件揭示了与不稳定性相关的相干波包的恒定相位线，以及间歇层流或湍流状态的高阴影光强局部区域。 连通网络组件的方向角被发现是识别与Mack模不稳定性相关的组件的合适度量，并能够详细表征不稳定性波包的波长和传播速度。 除了表征工作外，网络分析可以提供一个强大的框架，以理解间歇性的基本性质及其在层流到湍流流动转换过程中的作用。 显示英文摘要

摘要： Here we present a network theory-based approach to investigate the Mack-mode instability signature found in high-speed schlieren data from a Mach 6 laminar boundary layer flow over a $7^\circ$ cone. The data contain instability wave packets in the form of coherent rope-like structures which exhibit intermittency. The intermittency implies that conventional Fourier techniques are not particularly well suited for analysis. Network analysis, which is well known for handling episodic spatio-temporal data in a variety of complex systems, provides an alternate and more suitable framework. Techniques from time-varying spatial proximity networks are applied to the present data. The connected components in the network topology reveal lines of constant phase for coherent wave packets associated with the instability, and localized regions of high schlieren light intensity for intermittent laminar or turbulent flow states. The orientation angle of the connected network components is found to be a suitable metric for identifying components associated with the Mack-mode instability, and that enables detailed characterization of the wavelength and propagation speeds of the instability wave packets. Beyond the characterization exercise, network analysis can provide a powerful framework for understanding the fundamental nature of intermittency and its role in the laminar-to-turbulent flow transition process.