Dielectric-barrier-discharge vortex generators: characterisation and optimisation for flow separation control

Abstract

We investigated the use of dielectric-barrierdischarge plasma actuators as vortex generators for flow separation control applications. Plasma actuators were placed at a yaw angle to the oncoming flow, so that they produced a spanwise wall jet. Through interaction with the oncoming boundary layer, this created a streamwise longitudinal vortex. In this experimental investigation, the effect of yaw angle, actuator length and plasma-induced velocity ratio was studied. Particular attention was given to the vortex formation mechanism and its development downstream. The DBD plasma actuators were then applied in the form of co-rotating and counter-rotating vortex arrays to control flow separation over a trailing-edge ramp. It was found that the vortex generators were successful in reducing the separation region, even at plasma-to-freestream velocity ratios of less than 10%.

Reactive control of isolated unsteady streaks in a laminar boundary layer

“…In order to introduce the desired flow disturbance to counteract the disturbance induced by the upstream roughness element, a single pair of spanwise forcing plasma actuators was used, as shown in figure 3(b), with the forcing from each actuator oriented toward the other. This arrangement results in a pair of counter-rotating streamwise vortices, as demonstrated schematically in figure 3(b) and shown in detail by Jukes & Choi (2012, 2013. The result is low-speed streaks between the actuators with high-speed streaks on the outside, which are similar in shape but opposite in sign to the streaks generated by the isolated roughness element.…”

Plasma Virtual Actuators for Flow Control

“…Thus stronger vortices are created by long, stream wise-oriented DBD plasma VGs at high voltage and/or frequency. For practical use, however, DBD plasma VGs can be easily configured into VG arrays [5] [6]. Different types of array may be produced by simply changing the configuration of the lower electrode (see Figure 4).…”

“…DBD plasma VGs with staggered lower electrodes produce wall jets only on one side of each upper electrode, forming arrays of co-rotating vortices. Generally counter-rotating DBD plasma VGs are more effective for flow separation control due to larger wall-ward velocity component, but care should be taken to choose the correct spacing to prevent unfavorable interactions between adjacent vortices whilst maintaining sufficient coverage for effective flow control [5] [6].…”

“…Here, a trailing-edge flow separation was controlled and stall prevented up to α = 14.8˚ [8]. DBD plasma VG arrays have also been used to mitigate stall on a 20˚ backward facing ramp for W p /U ∞ > 7% (U ∞ < 15 m/s) [5].…”

Attenuation of Tollmien–Schlichting Waves Using Plasma Actuator Vortex Generators

“…Although numerous publications are available, they focus primarily on the topic of turbulent separation control (Jukes et al [1], Schatzman and Thomas [2], and Poggie et al [3]) and parametric studies (Jukes and Choi [4] and Wicks et al [5]). One publication that reports the use of plasma actuators for active vortex generation in laminar boundary layers concerns the damping of streaks produced by roughness elements (Hanson et al [6]).…”