Thermochemical Modeling of Nonequilibrium Oxygen Flows

Hypersonics;Nonequilibrium;Oxygen;CFD;Aerospace Engineering;Engineering;Aerospace Engineering

Neitzel, KevinGamba, Mirko ;

University of Michigan

关键词: Hypersonics;    Nonequilibrium;    Oxygen;    CFD;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/137049/kneitzel_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The development of hypersonic vehicles leans heavily on computational simulation due to the high enthalpy flow conditions that are expensive and technically challenging to replicate experimentally.The accuracy of the nonequilibrium modeling in the computer simulations dictates the design margin that is required for the thermal protection system and flight dynamics.Previous hypersonic vehicles, such as Apollo and the Space Shuttle, were primarily concerned with re-entry TPS design.The strong flow conditions of re-entry, involving Mach numbers of 25, quickly dissociate the oxygen molecules in air.Sustained flight, hypersonic vehicles will be designed to operate in Mach number ranges of 5 to 10.The oxygen molecules will not quickly dissociate and will play an important role in the flow field behavior.The development of nonequilibrium models of oxygen is crucial for limiting modeling uncertainty.Thermochemical nonequilibrium modeling is investigated for oxygen flows.Specifically, the vibrational relaxation and dissociation behavior that dominate the nonequilibrium physics in this flight regime are studied in detail.The widely used two-temperature (2T) approach is compared to the higher fidelity and more computationally expensive state-to-state (STS) approach.This dissertation utilizes a wide range of rate sources, including newly available STS rates, to conduct a comprehensive study of modeling approaches for hypersonic nonequilibrium thermochemical modeling.Additionally, the physical accuracy of the computational methods are assessed by comparing the numerical results with available experimental data.The numerical results and experimental measurements present strong nonequilibrium, and even non-Boltzmann behavior in the vibrational energy mode for the sustained hypersonic flight regime.The STS approach is able to better capture the behavior observed in the experimental data, especially for stronger nonequilibrium conditions.Additionally, a reduced order model (ROM) modification to the 2T model is developed to improve the capability of the 2T approach framework.