Secondary Instability of Stationary Crossflow Vortices in Mach 6 Boundary Layer over a Circular Cone

Abstract

Hypersonic boundary layer flows over a circular cone at moderate incidence can support strong crossflow instability. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7-degree half-angle circular cone in a Mach 6 free stream. Depending on the local amplitude of the stationary crossflow mode, the most unstable secondary disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of dominant secondary disturbances are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany.

Department(s)

Mechanical and Aerospace Engineering

Research Center/Lab(s)

Center for High Performance Computing Research

Report Number

NASA/TM-2015-218997

Document Type

Technical Report

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2015 Li, Fei; Choudhari, Meelan M.; Paredes-Gonzalez, Pedro; Duan Lian, All rights reserved.

Publication Date

01 Dec 2015

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