Effect Of Burst Ratio On Flow Separation Control Using A Dielectric Barrier Discharge Plasma Actuator At Reynolds Number 2.6 X 10(5)

In this study, the effect of the burst ratio (BR) on flow separation control using an alternating-current dielectric barrier discharge plasma actuator (DBDPA) was investigated. The effects of BR on the lift force on the NACA0015 airfoil were quantitatively evaluated by force measurements, and those on the flow field were measured by particle image velocimetry (PIV) and Schlieren visualisation. The force measurements showed that the recovery of the lift force decreased as BR increased, indicating that the flow separation control effect of the DBDPA decreased as BR increased. The PIV measurements showed that the temporal variation in vorticity was smaller at BR = 80% than at BR = 20% and that the vorticity did not change periodically at BR = 100%. Schlieren visualisation showed that DBDPA-induced flow produced a density gradient near the DBDPA electrode; the gradient was periodically observed and was found to be proportional to BR. In contrast, the density gradient in the separated shear layer varied at the end of each burst waveform, and the degree of variation decreased as BR increased. In addition, the root mean square value of the Schlieren signal intensity in the separated shear layer decreased with increasing BR. This result suggests that not only the strength and frequency of the disturbance input of the DBDPA but also the switching timing of the disturbance input are important for producing vorticity and thereby ensuring flow control.