Separation Control Using Vectoring Plasma Actuators

Abstract

The current study examines the use of plasma actuators as flow control devices, including synthetic jet actuators, jet vectoring, and vortex generation. The study of the plasma actuators applied to flat plates is conducted in quiescent conditions, as well as in the wind tunnel. There are two arrangements of plasma actuators investigated, one of which consists of an inner circular electrode embedded under a dielectric material and an outer annular electrode exposed to the atmosphere, and is used to create flow structures similar to that of a conventional synthetic jet actuator. The other arrangement is made up of a single linear electrode embedded within a dielectric material with a linear electrode on either side exposed to the atmosphere, and is used to create vectored jets and generate streamwise vortices. To create the plasma, the embedded electrode in each case is grounded while a high voltage, high frequency signal is applied to the exposed electrode(s). The benchtop experiments conducted primarily focus on the parametric study of jet vectoring, investigating the eects of the variation of input signal and geometry. The experiments conducted in the wind tunnel expand upon the benchtop, studying the uses of the jet vectoring plasma actuator in cross-stream flow, especially the use as a vortex generator jet (VGJ). For both the benchtop and wind tunnel investigations, the method of experimentation was done through PIV. It was found that through variations in the input signal, including voltage drop, frequency, and duty cycle, the jet created by the jet vectoring plasma actuator can be controlled over the entire 180 spectrum. While the plasma actuator investigated here demonstrates this ability, the attainable thrust vectoring angles are approximately 40 with respect to the surface. Varying pulsing frequency aects the type of jet produced by the jet vectoring plasma actuator. At low frequencies, the actuator produces two near wall jets in opposite directions, and at high frequencies, it produces a wall normal jet. There is a critical pulsing frequency at which the vortices created by each side of the actuator impinge on each other and nearly cancel. The portion of this study that was completed in the wind tunnel focused on the use of the plasma actuator previously discussed as a VGJ. The plasma actuator was placed on a flat alumina ceramic plate, and the eects of duty cycle, pulsing frequency, sideslip angle, and wind tunnel speed are investigated. The pulsing frequency is found to change the type of vortex or jet produced, similar to the benchtop results. Varying the sideslip angle slightly increases the vorticity created, but higher sideslip angles produce much less streamwise vorticity.