The spatial and temporal evolution characteristics of the density field near wall region actuated by plasma

Abstract

Using the dielectric barrier discharge plasma actuating model and high speed schlieren technique, the spatial and temporal characteristics of the density field near wall region actuated by plasma has been investigated in the different discharge modes and electrical parameters. Experimental results indicate that the initiation, development and dissipation of the induced vortex is an unsteady start-up process. After the equilibrium of body force and atmospheric damp is reached, the induced vortex stops accelerating and reaches maximum speed. The induced flow propagates downstream with the intermittent pulsed pattern in the pulsed discharge mode. However, in the steady discharge mode, plasma aerodynamic actuation cannot generate the closed vortex and the flow develops in a continuous turbulent form. Carrier voltage and the duty cycle are the key parameters that affect the vortex start position and maximum flow speed. With the increase of duty ratio, the start position of induced vortex moves downstream. There is a positive correlation between the excitation voltage maximum speed and the location of the maximum speed is pushed back with the rise of voltage. Pulse frequency is the dominant factor which determines the vortex generation frequency and the vortex generation frequency and pulse frequency is strictly consistent. We also find that the jumping change of flow speed resulted from pulsed discharge is the formation mechanism of induced vortex. Switching moment of actuator is the zero hour of vortex growth and duty ratio dominates the spatial structure and developmental pattern of induced vortex.