Adjoint-based sensitivity analysis for chemical non-equilibrium kinetics: application to O₂ + O system

This paper investigates the impact of different reaction mechanisms, from dissociation to exchange and inelastic processes, on the evolution of a O₂ +O chemical system at non-equilibrium in a 0D reactor at high temperatures. The problem is representative of shock-heated gas and it is of interest for hypersonic applications e.g., to understand the complex thermochemical processes occurring ahead a spacecraft entering the atmosphere. We perform an adjoint-based sensitivity analysis exploiting two different molecular internal models of increasing fidelity. Namely, the rovibrational State-to-State model and the Vibrational-Specific model. The sensitivity to the reaction rates is assessed for the global dissociation rate. Results offer insights concerning the impact of individual reaction coefficients on the objective function, providing an in-depth understanding of their role in the thermochemical evolution of the system.