Energy Accommodation Coefficient Calculation Methodology Using State-to-State Catalysis Applied to Hypersonic Flows

Abstract

The interplay of a gas-surface interaction and thermal nonequilibrium is still an open problem in aerothermodynamics. In the case of reusable thermal protection systems, it is unclear how much of the recombination energy is stored internally in the molecules produced by surface catalytic reactions, potentially leading to nonequilibrium between their translational and internal energy modes. A methodology is developed to calculate the energy accommodation coefficient using a rovibrational state-to-state chemical mechanism for a nitrogen mixture coupled with a generalized form of the catalytic recombination coefficient. The flow around a spherical body is simulated in hypersonic conditions, allowing study of the amount of energy deposited on the surface and stored in the recombining molecules. Internal energy quenching into translational energy is found, which is a phenomenon also observed experimentally, keeping the total energy transferred to the surface overall constant. The methodology developed for the application of a state-to-state model in the computational fluid dynamics framework coupled with catalysis is generic and applicable to a variety of other similar mechanisms.

Development of a Nitridation Gas-Surface Boundary Condition for High-Fidelity Hypersonic Simulations

“…1, II) MUTATION++ being open source, different CFD solvers share the same features, helping with code-to-code comparisons, as well regular updates of the library. The GSI module of MUTATION++ has been used to model catalytic and ablative materials, both assuming thermal equilibrium and non-equilibrium (state-to-state catalysis or two temperature ablation) of the gas near the surface [1,3]. In this work, we extend the library to use a finite-rate chemistry model derived from beam experiments [4], for describing, among other reactions, surface nitridation and nitrogen recombination [5].…”