Vibrational relaxation models for dilute shock heated gases Original Research Article

This work presents a computational examination of two models of vibrational relaxation for coupled vibration-dissociation-recombination processes. These models are commonly used in state-of-the-art non-equilibrium flow codes. A shock heated gaseous mixture of a single diatomic species highly dilute in a rare gas heat bath is considered. The master equation is linearized about final equilibrium and provides remarkable accuracy to early simulation times. The computations show a two-step relaxation of the vibrational energy. This behavior is not predicted by a linear relaxation rate equation. An exact expression for the rate of change of vibrational energy is presented and it is observed that both the linear relaxation rate equation and the Park diffusion model do not accurately reproduce the computed results.