Abstract
Effects of finite rate chemistry, radiative heat transfer, and turbulence radiation interactions (TRI) are assessed in a fully coupled manner in simulations of the Mach 20 Reentry F flight vehicle. Add-on functions were employed to compute a Planck mean absorption coefficient and the temperature self-correlation term (for TRI effects) in the optically thin shock layer. Transition onset was induced by specifying a wall roughness height at the experimentally observed transition location. The chemistry was modeled employing eight elementary reactions and an equilibrium approach allowing species to relax towards their chemical equilibrium values over the process characteristic time scale. The wall heat fluxes in the turbulent region, density, and velocity profiles compared reasonably well against measurements as well as similar calculations reported previously. The density predictions were more sensitive to the choice of modeling options than the velocities. The radiative source term magnitude agreed closely with its measurements deduced from shock tube experiments. The TRI model predicted a 60% enhancement in emission due to temperature fluctuations in the turbulent boundary layer. While the variations in density and velocity predictions among the models diminished along the length of the body, the O and NO prediction variations extended well into the turbulent boundary layer.
Highlights
Planetary entry vehicles are subjected to significant aerothermal heating as they dissipate their kinetic energy into the atmosphere of their destination planet
At certain reentry conditions radiative transfer can contribute both to the surface heat fluxes and to the cooling of the shock and boundary layers surrounding the vehicle depending on the spectral emission and absorption properties of the surrounding molecules [5, 6]
(4) Chemical equilibrium calculations without radiative transfer/turbulence radiation interactions (TRI) where the species were allowed to relax to their chemical equilibrium state depending on the characteristic time scale associated with the process
Summary
Planetary entry vehicles are subjected to significant aerothermal heating as they dissipate their kinetic energy into the atmosphere of their destination planet. The coupling between the radiation and the thermal field is accomplished in a loose coupling/decoupled manner [11] These approaches are Journal of Computational Engineering justified by facts that, at high reentry velocities, the radiative heat flux to the stagnation point is significant. The shock stand-off distance is small compared with the nose radius of vehicles, and a spatial change of physical properties is much more severe in the direction normal to the shock than in the tangential direction Since it is well known from simulations of combustion phenomena that a strong coupling between the fluid dynamics and radiative heat transfer is necessary to accurately predict the concentrations of minor species such as O, N, and NO [12, 13], this may hold true in hypersonic flows as well. The primary goals of this paper are as follows:
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