Date of Award

9-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Robert B. Greendyke, PhD

Abstract

Hypersonic vehicles require an accurate prediction of the transition of the boundary layer for the design of the thermal protection system due to the high heating rates under turbulent flow. Many thermal protection systems are carbon-based and introduce new species, specifically CO2, into the boundary layer flow which are known to dampen the instabilities that lead to transition for hypersonic vehicles. A Computation Fluid Dynamics study was accomplished examining the concentration of CO2 required to impact boundary layer transition over both sharp and blunt cones. These results were used in conjunction with air-carbon ablation models models to determine if these concentrations are possible through ablation alone and the impact on a flight representative vehicle transition. The study revealed that sufficient CO2 was present in the boundary layer at high enthalpy flow conditions to delay transition. Furthermore, a parametric study of the model uncertainties showed relative insensitivity to the gas-surface interaction model used but rather a high sensitivity to freestream flow parameters, vehicle geometry and surface temperature.

AFIT Designator

AFIT-ENY-DS-19-S-074

DTIC Accession Number

AD1083339

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