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Secondary Instability of Stationary Crossflow Vortices in Mach 6 Boundary Layer Over a Circular ConeHypersonic 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.
Document ID
20160002215
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Fei Li
(Langley Research Center Hampton, Virginia, United States)
Meelan M Choudhari ORCID
(Langley Research Center Hampton, Virginia, United States)
Pedro Paredes-Gonzalez ORCID
(Langley Research Center Hampton, Virginia, United States)
Lian Duan
(Missouri University of Science and Technology Rolla, Missouri, United States)
Date Acquired
February 23, 2016
Publication Date
December 1, 2015
Publication Information
Publisher: National Aeronautics and Space Administration
Subject Category
Aerodynamics
Report/Patent Number
L-20650
NF1676L-23272
NASA/TM-2015-218997
Funding Number(s)
WBS: 109492.02.07.01.01
Distribution Limits
Public
Copyright
Use by or on behalf of the US Gov. Permitted.
Keywords
Boundary layer flow
Circular cones
Cross flow
Stability
Vortices
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