Date of Award

3-2023

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Robert B. MacDermott, PhD

Abstract

To investigate the potential for relaminarization in the near-wake of a 7-degree half-angle cone, a series of hypersonic wake experiments were conducted in the Air Force Research Laboratory Mach 6.1 Ludwieg tube. Relaminarization is a spatial phenomenon that occurs when a turbulent flow reverts to a laminar-like state at a downstream location, where turbulent fluctuations negligibly contribute to average flow properties. Although relaminarization has been documented in subsonic and supersonic flows, the current body of knowledge related to the occurrence of, and mechanisms that drive, relaminarization at hypersonic speeds is sparse. Measurements were obtained across a range of freestream unit Reynolds numbers using z-type schlieren, self-aligned focused schlieren, and surface-mounted pressure sensors. Boundary layer turbulence transition characteristics were also adjusted with interchangeable nose tips. Streamlined flow was potentially observed at approximately 9 cm downstream of turbulent boundary-layer flow at the cone trailing edge during z-type schlieren testing, which may indicate flow relaminarization. These results were not fully confirmed during self-aligned focused schlieren testing. Additionally, laminar, transitional, and turbulent boundary layer flows were observed expanding into the near-wake region. Rope-like structures, reminiscent of Mack’s second mode, and wisp-like instability structures were also observed. The results of these studies set the stage for future relaminarization investigations.

AFIT Designator

AFIT-ENY-MS-23-M-291

Comments

A 12-month embargo was observed.

Approved for public release. Case number on file.

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