Experimental study of separation bubble control behind a backward-facing step using plasma actuators

In this paper, controlling flow around a backward-facing step by means of a dielectric barrier discharge plasma actuator is experimentally investigated. The pressure distribution on the step surface as well as the natural oscillations of the flow in the shear layer at three different Reynolds numbers from 18,000 to 54,000 (based on the step height) are measured in the wind tunnel. Then, by installing plasma actuators at different positions, the changes in pressure distribution and the length of the separation bubble are investigated. It was found that for controlling the separation bubble and expediting the flow recovery process the best position for installation of the plasma actuator is the upstream of the separation point i.e., step tip edge. Installing the actuator inside the separation bubble has a relatively low effect on the separation zone length. In addition, the most effective way for exciting the shear layer is utilizing the unsteady actuation with an exciting frequency equal to the natural frequency of the vortex shedding.