Dissociation and energy transfer study of N₂(¹Σ⁺ _g)-N(⁴S_u) and N₂(¹Σ⁺ _g -N₂(¹Σ⁺ _g) interactions by using rovibrational and coarse-grained state-to-state

The present work aims at studying dissociation and energy transfer in N₂(¹Σ⁺ _g)-N(⁴S_u) and N₂(¹Σ⁺ _g -N₂(¹Σ⁺ _g) interactions by means of rovibrational and coarse-grained state-tostate models. Kinetic and thermodynamic data are taken from the database developed by the Computational Quantum Chemistry Group at NASA Ames Research Center. The coarse-grained models are developed by grouping the energy levels into bins where the population distribution is assumed Maxwell-Boltzmann at its own temperature. Different grouping strategies are investigated. The governing equations are obtained by taking the zeroth and first-order moments of the rovibrational master equations. The accuracy of the proposed models is tested against the rovibrational master equation solution for both flow quantities and population distributions. Applications to flows behind normal shock waves and isothermal chemical reactors demonstrate that average gas properties can be accurately predicted by adopting the proposed bin collisional models. It is also shown that a multi-temperature approach leads to an underprediction of dissociation, due to the inability of the former of accounting for the faster excitation of high-lying rotational and vibrational states.