Numerical simulation of flow control around a rectangular cylinder by dielectric barrier discharge plasma actuators

Abstract

The control mechanism of a dielectric barrier discharge plasma actuator is investigated via direct numerical simulations in the flow field around a square cylinder. The Reynolds number is 33 000. Conditions for the burst frequency of the actuator are explored in terms of the reduction rate of drag and root mean square (RMS) lift coefficients. A good control effect is achieved, and vortex shedding is fairly repressed at Stb (Strouhal number for the burst frequency) = 0.50. The flow induced by the actuator generates two vortices: the first and second vortices. Until the next actuator on-time, the second vortex grows on the upper or lower side of the cylinder. The second vortex collides with the first vortex, and both vortices flow downstream in a straight line. This situation happens almost simultaneously on the upper and lower sides of the cylinder; thus, a high reduction rate of RMS lift and drag coefficients can be obtained. A control effect is obtained at Stb = 2.00, which is lower than that at Stb = 0.50, where a tiny vortex is raised by the flow induced by the small actuator on-time and flows downstream at a small distance away from the cylinder. The least control effect is achieved at Stb = 0.25 because the collision between the first and second vortices does not occur due to a large actuator off-time. The duration of on-time and off-time is important for determining the burst frequency for the most effective control.