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 Bow of nit rogen in tile 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 m ethod. The effects of single- and multiple-quantum vibration-translati on 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 vi brational distributions are present in the flow field, and that the fo rced-harmonic oscillator model predicts that dissociation occurs from the low vibrational levels only. (C) 1997 American Institute of Physic s.