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Benjamin R. Bettis
Missouri University of Science and Technology
Advisor: Dr. Serhat Hosder
Abstract
There can be many sources of uncertainty in hypersonic flow simulations such as physical modeling, the stochastic nature of the inputs, and even numerical errors. This manuscript examines uncertainty in the aeroheating to a generic hypersonic reentry vehicle due to uncertainties in the freestream velocity and catalytic wall reaction efficiency using a high fidelity computational fluid dynamics (CFD) solver for high temperature gas in thermo-chemical non-equilibrium. Initially, both stochastic variables were assumed to be aleatory, and the uncertainty was propagated using point-collocation non-intrusive polynomial chaos (NIPC) and an analytical response surface was formulated. Using the response surface, the catalytic efficiency was modeled as an epistemic uncertain variable, and second order probability method was used to propagate the mixed aleatory-epistemic uncertainty through the CFD simulations. To help validate these uncertainty methods, they were first applied to the Fay-Riddell relation for calculating stagnation point heat transfer. Results of the validation study demonstrated the efficiency of NIPC and showed the relative comparison between aleatory and epistemic uncertainty modeling. The results from the CFD simulations have shown that there is a large amount of uncertainty in the heat transfer to the surface of the reentry vehicle. Therefore, these uncertainties must be accounted for in the safe and reliable design of a hypersonic reentry vehicle. In future studies, other types of epistemic uncertainty propagation methods may be implemented, such as Dempster-Shafer theory of evidence, to help validate the results from the second order probability theory.
Benjamin Bettis is originally from Hillsboro, MO. He is currently working towards his M.S. in Aerospace Engineering at Missouri S&T. After graduating in December 2010, he plans on staying in school to acquire a Ph.D. in Aerospace Engineering. After school, he hopes to find a career that is both challenging and exciting. He looks forward to what the future may bring, and hopes to find joy in all of his future endeavors.
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