Nitric Oxide Spectroscopic Measurements in a Hypervelocity Stagnation Flow

Abstract

Spatially resolved emission spectra are collected along the stagnation streamline of hypervelocity flow over a circular cylinder. Excitation temperatures are extracted from the NO γ band (A^2Σ^+ - Χ^2Π) emission at downstream locations behind the bow shock. The result is a temperature relaxation profile that quantifies the state of thermal non-equilibrium. Results are compared against a zero-dimensional state-to-state model and a two-temperature, reacting Navier-Stokes simulation. Test gas O_2 mole fraction is varied from 30% to 120% of the air value to examine changes in relaxation profile.

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