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Ph.D. Thesis Proposal by
Pratibha Raghunandan
(Advisor: Prof. Stephen M. Ruffin)
“Internal Energy Modeling of Hypersonic Weakly Ionized Non-Equilibrium Flows”
May 1, 2017 @ 3 p.m.
Weber 200
Abstract:
The dissociation and ionization of gases in high temperature flows, typical for planetary re-entry vehicles, require computation of finite rate chemistry and thermal non-equilibrium. This work presents the implementation of non-equilibrium flow physics capabilities in an unstructured Cartesian grid-based adaptive solver. The thermo-chemical non-equilibrium solver incorporates multiple multi-temperature models that simulate various types of energy exchanges between the constituent atoms/ molecules. The modeling of such energy exchanges can provide different effective temperatures to define a chemical reaction, which in turn can yield significant differences in non-equilibrium chemical and thermal relaxation rates.
A two temperature model, involving a single translational and a single vibrational temperature, is compared to a multi-vibrational, single translational model for different gases/gaseous mixtures; the effects of composition of gases on the relaxation rates are discussed for these cases. Furthermore, the effects of the inclusion of a separate electron temperature on the vibration-translation relaxation rates in ionized flows are discussed. The study of the differences brought about by such relaxation rates in two-dimensional thermo-chemical non-equilibrium flows is proposed.
The thermo-chemical non-equilibrium modeling in hypersonic flows yields considerable differences in resultant chemistry and shock stand-off distances in comparison with chemical non-equilibrium flows, and significant differences with equilibrium models. This particularly has an impact on the prediction of electron and ion densities in weakly ionized gases, the accurate modeling of which are very important for radio blackout mitigation and plasma-aerodynamic flow control. It is identified that accurate modeling of energy exchanges at the macroscopic level along with the simulation of thermal inhomogeneities are imperative to successfully replicate ground-based tests in a computationally efficient manner, as well as capture the flow physics associated with shock waves traveling through weakly ionized gases. This proposed work will investigate such underlying physics through the appropriate modeling of internal energy for the high speed flows of interest.
Committee:
Dr. Stephen Ruffin (Advisor)
Dr. Suresh Menon
Dr. Wenting Sun
