ORCID Identifier(s)

0009-0000-4827-6944

Graduation Semester and Year

Spring 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Aerospace Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Dr. Luca Maddalena

Abstract

Sustained hypersonic flight is an exceedingly challenging task comprised of a myriad of complex physical processes. At hypersonic speeds, which is defined by the presence of unique phenomena like high-temperature nonequilibrium flow, viscous and vorticity interactions, and thin shock layers, which are not seen in supersonic, transonic, or subsonic vehicles, the vehicle design is principally driven by the high levels of aerodynamic heating caused by the conversion of kinetic energy to internal energy. Gaining an understanding of how these physical processes interact with each other is required to develop a design methodology for this class of vehicles. Arc-jet wind tunnels are chosen for hypersonic flow fundamental science research and hypersonic flight vehicle development due to their unique ability to capture the relevant aerothermochemical processes on time scales necessary for research and development (R&E) and testing and evaluation (T&E) of thermal protection systems (TPS), advanced air-breathing propulsion technologies, and other critical flight sub-systems like optics/sensors and communication/data transfer strategies. As the arc-jet wind tunnel facilities reproduce the hypersonic flight environments’ exceedingly harsh aerothermal-mechanical loading, determining critical flow properties such as velocity, temperature, pressure, and chemical composition is challenging. This work presents advances in both intrusive and nonintrusive diagnostic techniques for characterization of high-enthalpy flow. First, an approach to the design, and successful experimental validation, of a slug-type calorimeter for long-duration high-enthalpy flows is presented. Next, the direct measurement of skin friction in an arc-jet flow environment and associated design methodology is presented. Lastly, the world first application of hybrid femtosecond/ picosecond Coherent Anti-Stokes Raman Scattering (fs/ps-CARS) to measure the vibrational temperature of molecular nitrogen in an arc-jet environment is detailed. This work has demonstrated the capability of fs/ps-CARS to overcome the challenges posed by the intense background radiation and the spatial and temporal precision required for successful implementation in arc-jet flows. The diagnostic techniques and instrumentation developed in this dissertation represent a step forward in the field’s capability to characterize and understand high-enthalpy flows. By providing detailed, accurate measurements of critical flow properties, this work supports the advancement of hypersonic vehicle design and testing.

Keywords

arc-jet, flow characterization, hypersonics, laser-based diagnostics

Disciplines

Aerodynamics and Fluid Mechanics | Optics | Propulsion and Power | Space Vehicles

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Available for download on Wednesday, May 14, 2025

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