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Nosetip Bluntness Effects on Transition at Hypersonic Speeds: Experimental and Numerical Analysis Under NATO STO AVT-240The existing database of transition measurements in hypersonic ground facilities has established that the onset of boundary layer transition over a circular cone at zero angle of attack shifts downstream as the nosetip bluntness is increased with respect to a sharp cone. However, this trend is reversed at sufficiently large values of the nosetip Reynolds number, so that the transition onset location eventually moves upstream with a further increase in nosetip bluntness. This transition reversal phenomenon, which cannot be explained on the basis of linear stability theory, was the focus of a collaborative investigation under the NATO STO group AVT-240 on Hypersonic Boundary-Layer Transition Prediction. The current paper provides an overview of that effort, which included wind tunnel measurements in three different facilities and theoretical analysis related to modal and nonmodal amplification of boundary layer disturbances. Because neither first and second-mode waves nor entropy-layer instabilities are found to be substantially amplified to initiate transition at large bluntness values, transient (i.e., nonmodal) disturbance growth has been investigated as the potential basis for a physics-based model for the transition reversal phenomenon. Results of the transient growth analysis indicate that disturbances that are initiated within the nosetip or in the vicinity of the juncture between the nosetip and the frustum can undergo relatively significant nonmodal amplification and that the maximum energy gain increases nonlinearly with the nose radius of the cone. This finding does not provide a definitive link between transient growth and the onset of transition, but it is qualitatively consistent with the experimental observations that frustum transition during the reversal regime was highly sensitive to wall roughness, and furthermore, was dominated by disturbances that originated near the nosetip.
Document ID
20190000426
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Pedro Paredes ORCID(Langley Research Center Hampton, Virginia, United States)
Meelan M Choudhari ORCID(Langley Research Center Hampton, Virginia, United States)
Fei Li (Langley Research Center Hampton, Virginia, United States)
Joseph S Jewell ORCID(United States Air Force Research Laboratory Wright-Patterson AFB, Ohio, United States)
Roger L Kimmel (United States Air Force Research Laboratory Wright-Patterson AFB, Ohio, United States)
Eric C Marineau (Arnold Engineering Development Complex Silver Spring, Maryland, United States)
Guillaume Grossir (Von Karman Institute for Fluid Dynamics Sint-Genesius-Rode, Belgium)
Date Acquired
February 5, 2019
Publication Date
January 8, 2018
Publication Information
Publication: 2018 AIAA Aerospace Sciences Meeting
Publisher: American Institute of Aeronautics and Astronautics
e-ISBN: 9781624105241
DOI: 10.2514/6.2018-0057
Subject Category
Aerodynamics
Report/Patent Number
NF1676L-27370
AIAA-2018-0057
Meeting Information
Meeting: AIAA SciTech Forum and Exposition
Location: Kissimmee, FL
Country: US
Start Date: January 8, 2018
End Date: January 12, 2018
Sponsors: American Institute of Aeronautics and Astronautics
Funding Number(s)
WBS: 109492.02.07.01.01
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Numerical analysis
Hypersonic speed
Freestream Mach Number
Laminar turbulent transition
Arnold Engineering Development Complex
Angle of attack
Kinetic energy
Parabolized stability equations
Stagnation pressure
Hypervelocity wind tunnels

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