Stability and modal analysis of shock/boundary layer interactions

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• 作者：Joseph W. Nichols ; Johan Larsson…
• 关键词：Shock/boundary layer interactions ; Global stability analysis ; Dynamic mode decomposition
• 刊名：Theoretical and Computational Fluid Dynamics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：31
• 期：1
• 页码：33-50
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Engineering Fluid Dynamics; Classical and Continuum Physics; Computational Science and Engineering;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-2250
• 卷排序：31

文摘

The dynamics of oblique shock wave/turbulent boundary layer interactions is analyzed by mining a large-eddy simulation (LES) database for various strengths of the incoming shock. The flow dynamics is first analyzed by means of dynamic mode decomposition (DMD), which highlights the simultaneous occurrence of two types of flow modes, namely a low-frequency type associated with breathing motion of the separation bubble, accompanied by flapping motion of the reflected shock, and a high-frequency type associated with the propagation of instability waves past the interaction zone. Global linear stability analysis performed on the mean LES flow fields yields a single unstable zero-frequency mode, plus a variety of marginally stable low-frequency modes whose stability margin decreases with the strength of the interaction. The least stable linear modes are grouped into two classes, one of which bears striking resemblance to the breathing mode recovered from DMD and another class associated with revolving motion within the separation bubble. The results of the modal and linear stability analysis support the notion that low-frequency dynamics is intrinsic to the interaction zone, but some continuous forcing from the upstream boundary layer may be required to keep the system near a limit cycle. This can be modeled as a weakly damped oscillator with forcing, as in the early empirical model by Plotkin (AIAA J 13:1036–1040, 1975).