Multi-mode instabilities arising in hypersonic flow conditions for aerospace applications
Date
2024
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Publisher
University of Delaware
Abstract
Research in hypersonic aerodynamics is important in understanding the practicality of sustained high-speed flight and the design parameters of such vehicles. Hypersonic boundary layer transition is dominated by the presence of various disturbance (Mack) modes present within the boundary layer which undergo by modal growth and eventually transition the flow to turbulence. Understanding these dynamics of these modes and their interactions within the boundary layer can bridge the knowledge gaps in the fundamental causes of heat transfer, friction drag, lift and other properties which become critically important in hypersonic flight. ☐ The aim of this research is to perform a analytical study utilizing computational fluid dynamics (CFD) coupled with boundary layer stability analysis employing linear stability theory (LST) and parabolized stability equations (PSE) to help understand the dynamics of Mack modes and their nonlinear interactions. One question to be studied is the source of energy driving the 1st and 2nd mode instabilities. A characterization of the energetics of the 1st and 2nd modes was performed at various flow conditions to further understand physical mechanisms governing the modal growth pathway to transition, and was shown that the traditional 1st mode definition is incomplete. A design study into a geometry conducive to 1st and 2nd mode interactions was performed and investigated. With such a geometry, the dynamics between a 1st mode dominated boundary layer with an existing 2nd mode was investigated. Finally, with understanding of the thermoacoustic interpretation of the 2nd mode, a impedance boundary condition is applied to a canonical conical geometry in an attempt to analyze its effect on certain unstable waves within the boundary layer. Understanding the dynamics of these modes and their interactions within the boundary layer can bridge fundamental knowledge gaps governing various phenomena in hypersonic flight.
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Keywords
Boundary layer transition, Hypersonic flight, Parabolized stability equations, Linear stability theory, Computational fluid dynamics