Date of Award

3-21-2019

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Mark F. Reeder, PhD

Abstract

High-speed Schlieren photography was utilized to visualize flow in the Air Force Research Laboratory Mach 6 Ludwieg tube facility. A 7° half-angle cone/flare model with variable nosetip radius and flare angle options was used in the study. Testing was performed at two driver tube pressures, generating freestream Reynolds numbers of 10.0x106 and 19.8x106 per meter. The variable-angle flare portion of the model provided a method for adjusting the intensity of the adverse pressure gradient at the cone/flare junction. As expected from existing literature, boundary layer separation along the cone frustum occurred further upstream as the magnitude of the adverse pressure gradient increased. Imaging of the four cone tip radii revealed a slightly positive angle of attack for the model. This conclusion was supported by asymmetrical heating contours observed in a prior infrared thermography study on the same model. Measurements of the bow shock angles downstream of the cone tip verified Mach 6 flow from the Ludwieg tube nozzle when analyzed using Taylor-Maccoll theory. Blunt cone tips generated laminar boundary layers along the cone frustum. These laminar boundary layers led to unstable behavior in the recirculation region at the cone/flare junction. Analysis of the instability revealed loosely cyclical behavior. Pressure data from the model surface would provide much greater insight into local boundary layer behavior. Future hypersonic vehicles will inevitably include numerous adverse pressure gradients. A full understanding of these regions is imperative to successful design and flight testing.

AFIT Designator

AFIT-ENY-MS-19-M-226

DTIC Accession Number

AD1073757

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