Thermomechanical Relaxation of Vibrationally Excited Nitric Oxide in a Hypersonic Turbulent Boundary Layer

The effects of thermal nonequilibrium are studied using a direct current glow discharge plasma to selectively modify the vibrational temperature of an otherwise cold flow. These experiments were performed at [Formula: see text] and [Formula: see text] in the Actively Controlled Expansion tunnel at Texas A&M University on a canonical 2.75° half-angle wedge test article. An [Formula: see text] plasma was generated across spanwise electrodes, and removable trips produced either a laminar or turbulent boundary layer. Nitric oxide planar laser-induced fluorescence (NO PLIF) quantified the extent of the [Formula: see text] vibrational perturbation due to the plasma and its subsequent interplay with the boundary layer, the first such data of which the authors are aware. NO PLIF measurements were taken at three locations along the test article, and quasi-temperature measurements are reported at each. Despite not quantifiably perturbing the boundary layer, the plasma was shown to alter the NO vibrational temperature profile therein. Independent analysis of the thermodynamics and fluid mechanics of the system suggests each set of physics could explain the results observed near and far from the wall, respectively.