Reduced-order modeling for non-equilibrium air flows

This work deals with the development and application of reduced-order models for nonequilibrium hypersonic air flows. Starting from a State-to-State formulation, the reduction of kinetics mechanism to a more tractable form for Computational-Fluid-Dynamics (CFD) applications is realized by grouping the atom/molecule internal states within bins with prescribed population distributions. The group/bin-averaged kinetic parameters (e.g., rate coefficients) are computed in conjunction with Quasi-Classical-Trajectory (QCT) calculations. This allows for treating diatom-diatom systems (e.g., N₂-N₂) for which a State-to-State method is simply impractical. The proposed physico-chemical models are first compared against State-to-State formulations in zero and one-dimensional configurations to assess their accuracy, and later applied to realistic multi-dimensional simulations to demonstrate their maturity and predictive capabilities.