Detailed simulation of nitrogen dissociation in stagnation regions

Vibrational relaxation rates from Schwartz-Slawsky-Herzfeld theory and the forced-harmonic oscillator model are used to study the flow of nitrogen in the stagnation region of a blunt body. The mass conservation equations are coupled to the momentum and total energy equations, and solved using an implicit finite-volume computational fluid dynamics method. The effects of single- and multiple-quantum vibration-translation transitions and vibration-vibration transitions are studied. Also, the effect of the mass diffusion of the excited oscillators across the shock layer is investigated. It is found that highly non-Boltzmann vibrational distributions are present in the flow field, and that the forced-harmonic oscillator model predicts that dissociation occurs from the low vibrational levels only.