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ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
AN ASSESSMENT OF GRID REFINEMENT IN THERMOCHEMICAL NON-EQUILIBRIUM HYPERSONIC REENTRY FLOWS
Submission Author:
Farney Moreira , SP
Co-Authors:
Farney Moreira, William Wolf, João Luiz F. Azevedo
Presenter: Farney Moreira
doi://10.26678/ABCM.ENCIT2022.CIT22-0484
Abstract
The atmospheric reentry procedure is a topic of great importance for space missions. Hypersonic vehicles enter the Earth’s atmosphere at very high speeds, and kinetic energy is converted into internal energy in the reentry process. Realistic flight conditions involve several physical mechanisms including the formation of strong shock waves besides chemical reactions of dissociation, recombination and ionization. If the reentry velocity and the altitude are sufficiently high, the chemical reactions occur in thermodynamic non-equilibrium and high temperature shock layers are formed near the vehicle surface, leading to vibrational, rotational and translational excitation of molecules. The shock layers typically exist behind the strong shock waves that substantially increase the gas temperature, affecting operational flight issues related to the thermal protection system (TPS). In the present work, numerical simulations are presented for the Fire II capsule under hypersonic flow conditions including thermodynamic nonequilibrium. Here, the air is considered as the gas mixture, which is modeled as a combination of oxygen and nitrogen. A mesh refinement study is performed in the region adjacent to the thermodynamic and chemical non-equilibrium regions. In this sense, this study will provide the best practices in terms of mesh refinement for reactive flows under hypersonic conditions. Two wall boundary conditions, catalytic and non-catalytic, are tested and their results are compared to experimental data available in terms of the convective heat flux. The Navier-Stokes equations are solved using the finite volume method including Park’s two-temperature model. Results are presented in terms of the thermodynamic non-equilibrium level of the gas mixture along the flow axisymmetric line and a comparison between simulations and experimental data will be provided in terms of heat flux at the stagnation point.
Keywords
Hypersonic Flow, Atmospheric reentry, Heat transfer, Reactive flows, Thermodynamic non-equilibrium
