Direct molecular simulation of dissociating oxygen-nitrogen mixture in space-homogeneous reactor

Erik Torres, Thomas E. Schwartzentruber

DOI Number XXX-YYY-ZZZ

Conference Number HiSST-2022-75

In this paper we present first-principles direct molecular simulations (DMS) of rovibrational excitation and
dissociation of five-species air (N2, O2, NO, N, O) mixtures in constant-volume reactors under isothermal
and adiabatic conditions. Our simulations are restricted to a static gas in space-homogeneous reservoirs
without flow coupling, but we carefully choose initial conditions to mimic the nonequilibrium state encountered behind strong shock fronts, such as the ones generated in shock-tube facilities, or ahead of
hypersonic flight vehicles. We examine non-Boltzmann effects in the rotational and vibrational energy
distributions of the O2-, N2 and NO-molecules, as well as the temperatures associated with their rotational and vibrational modes during the quasi-steady-state dissociation regime. By examining probability
density distributions of the diatomic species consumed in the dissociation and the Zel’dovich exchange
reactions, we are able to assess their degree of rovibrational biasing. It is found that all dissociating
diatoms exhibit a strong preference toward internal energies near the dissociation limit, whereas the
same does not happen in the exchange reactions.

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ab initio potential energy surfaces, direct molecular simulation, molecular dissociation, thermo-chemical nonequilibrium, Zel’dovich reactions

In Categories: 1.Events, High-Speed Aerodynamics and Aerothermodynamics, HiSST 2022

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