VIBRATIONAL-RELAXATION MODELS FOR DILUTE SHOCK-HEATED GASES

This work presents a computational examination of two models of vibrat ional relaxation for coupled vibration-dissociation-recombination proc esses. These models are commonly used in state-of-the-art non-equilibr ium flow codes. A shock heated gaseous mixture of a single diatomic sp ecies 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 b y a linear relaxation rate equation. An exact expression for the rate of change of vibrational energy is presented and it is observed that b oth the linear relaxation rate equation and the Park diffusion model d o not accurately reproduce the computed results.