State-Specific Dissociation Modeling in Hypersonic Blunt Body Flow

Abstract

Numerical simulations are presented of steady state, hypersonic blunt body nitrogen ∞ow for conditions under which there is considerable thermal dissociation. The internal energy relaxation processes of vibrational energy transfer and dissociation were treated using state-to-state kinetics of diatomic nitrogen. To gain understanding of the role of vibrational-translational (VT) rates on dissociation, the vibrational-translational rates were implemented in a ladder climbing model and the efiect of vibrational bias on dissociation was investigated. For temperatures up to 25,000 K, a simplifled depletion model with two difierent sets of VT rates established the sensitivity of depletion to the relative magnitude of VT and dissociation rates for dissociation in nitrogen. State-speciflc VT and dissociation rates were incorporated into a solution of the master kinetic equations and coupled to the ∞uid dynamic equations to describe the thermo-chemical nonequilibrium phenomenon in high temperature hypersonic ∞owflelds. The ∞owfleld consists of a Mach 19.83 nitrogen ∞ow past a hemisphere cylinder of radius 0.1524 m. The full state-speciflc dissociation model consisting of 48 quantum levels in the vibrational manifold was coupled to the ∞uid dynamic equations. For temperatures in the shock layer ranging from 9,000 K to 21,000 K, the dissociation primarily takes place from the lower energy levels.