Supersonic Nonequilibrium Plasma Wind-Tunnel Measurements of Shock Modification and Flow Visualization

Abstract

Experiments conducted in a new, small-scale, nonequilibrium plasma wind tunnel recently developed at Ohio State University are discussed. The facility provides a steady-state supersonic e ow of cold nonequilibrium plasma with well-characterized, near uniform, properties. The plasma is produced in aerodynamically stabilized highpressureglowdischargethatformstheplenumofthesupersonicnozzle.Thepossiblemodie cation ofthesupersonic e ow due to ionization is studied by measuring the angle of oblique shocks attached to the wedge located in the nozzle test section. The results do not show any detectable shock weakening or attenuation in weakly ionized nitrogen plasma, compared to the measurements in a nonionized gas e ow. Experiments in supersonic e owing nitrogen and helium afterglow also demonstrate a novel technique for high-density supersonic e ow visualization. It allows identifying all key features of the supersonic e ow, including shocks, boundary layers, e ow separation regions, andwakesby recording intensevisibleradiation of theweakly ionizedplasmas.Interpretation ofradiation intensitydistributionsinnonequilibriumsupersonice owingafterglowmayprovideinformationonkeymechanisms of energy storage and ultraviolet radiation in high-altitude rocket plumes. In addition, these e ow visualization experiments can be used for validation of multidimensional computer e ow codes used for internal e ow simulation.