Influence of a Counterflow Plasma Jet on Supersonic Blunt-Body Pressures

Abstract

Aerodynamic augmentation in the presence of a thin high-temperature onboard plasma jet directed upstream of a slightly blunted cone was studied experimentally and numerically. The flow around a truncated cone cylinder at zero incidence was considered for Mach numbers M∞ = 2.0, 2.5, and 4.0. For the first time, computationally validated experimental pressure distributions over the model surface in the presence of the plasma jet were obtained. As in the conventional (nonplasma) counterflow jet, two stable operational regimes of the plasma jet were found. These were a short penetration mode and a long penetration mode (LPM) aerospike into the opposing supersonic freestream. The greatest drag reduction occurred in the moderate LPM regime. LPM strong overblowing reduces the benefits. The experimental pressure results were approximately validated against an Euler computational fluid dynamics simulation, modeling a perfect gas hot jet, counterflowing against a perfect gas supersonic freestream. Plasma effects such as electron pressure, radiation, electric field interactions, Joule heating, and induced vorticity, streamers, and plasmoids have been identified that, if accounted for, may improve the comparison. Procedures for the use of these experimental results have been outlined as a baseline that will be useful in separating fluid dynamic/thermal effects from plasma processes in understanding the physics of onboard plasma jets for aerodynamic augmentation.