Maximum entropy quadratic model to characterize chemical non-equilibrium in re-entry flows

This thesis presents the study of an advanced non-equilibrium model for state-specific chemical kinetics based on method of moments. The focus of this project is on the rovibrational chemical kinetics of the N2-N system. Internal excitation, dissociation, recombination and energy transfer reactions, which are important processes in aerothermodynamics, are studied. The kinetic and thermodynamic data is obtained from ab-initio calculations performed at NASA Ames Research Center. Previous analysis of the population distribution revealed that the population of the low lying energy levels of nitrogen molecules strongly deviates from a Boltzmann distribution, and the non-equilibrium distribution exhibits significant curvature. By invoking the maximum entropy principle subject to a series of constraints, the logarithm of distribution function is reconstructed using quadratic functions in the internal energy space of the molecular species. The results of the numerical simulations for an ideal chemical reactor show that the quadratic model captures the excitation and dissociation profiles accurately by using only three to seven groups thereby reducing the computational costs for non-equilibrium flow simulations significantly