Control of unsteady flow separation over a circular cylinder using dielectric-barrier-discharge surface plasma

Dielectric-barrier-discharge plasma actuators have been used to control the unsteady flow separation over a circular cylinder at Re=15 000 with a view to maximizing the lift with a minimum drag increase. The flow structure was studied using time-resolved particle image velocimetry and flow visualization, while the dynamic lift and drag were simultaneously measured with a two-component force balance. Our results show that the lift can be dramatically increased by a single, short-duration pulse of plasma at carefully chosen location and timing. A peak lift coefficient of 1.24 was observed, showing that the plasma can increase lift by over 300%, with less than 25% increase in drag. Optimal conditions occurred when the actuator was located at 75° from the streamwise axis, with plasma forcing timed to coincide with the retreat of the separation point. This corresponds to the actuator being located 7° upstream of the natural separation point. The peak lift was relatively insensitive to the duration of the plasma.