Fundamental study on plasma-assisted flow control at external nozzle of high-speed transport vehicle*

This study explores the effect of dc plasma-assisted rapid flow control on the flow structure over 15-degree external nozzle surface connected at rear side of supersonic linear spike nozzles. An external nozzle is a part of rear fuselage surface structure that navigates exhaust gas from the engine. Typically, around a quarter of the total thrust is produced at the external nozzle surface and thereby flow control at the external nozzle area can have significant impact on vehicle's aerodynamic control and can be a feasible solution for rapid and effective aerodynamic control method. A major attention is focused on transient phenomena related to plasma-flow interaction. Experiments were conducted in supersonic wind tunnel at Mach numbers of 2 and 5. 0.2-second steady pulse plasma was generated at pairs of electrodes installed and flush-mounted in a crossflow direction in front of the expansion ramp model that represents the external nozzle. The transient flow structure and plasma behavior were visualized with schlieren method and high speed camera to clarify the flow and plasma interaction. The surface pressure distribution on the wall, especially at the front and rear side of electrodes and at the ramp, was measured with fast pressure transducers. DC plasma generated in the front, upstream side, of the external nozzle ramp shifts the shock position from the ranp to the electrode location, subsequently forming a small separation zone and resulting in significant pressure change behind electrodes. Pressure change was characterized as a function of flow/plasma parameters.