Effect of a DC surface-corona discharge on a flat plate boundary layer for air flow velocity up to 25 m/s

Abstract

The ability to actively modify a low-velocity airflow along a flat plate by a DC surface-corona discharge is experimentally analysed. This electrofluiddynamic (EFD) actuator consists of two electrodes flush mounted on the insulating surface of the plate in order to create a tangential corona discharge at close vicinity to the wall, usually in the direction of the airflow. In this paper, velocity profiles within the boundary layer of the flat plate are presented for a free air stream velocity U 0 of up to 25 m/s ( Re≈375,000). On one hand, the velocity profiles show that the ionic wind induced by the corona discharge results in a velocity increase inside the boundary layer when the ionic wind and the free air stream are in the same direction. On the other hand, the velocity at the wall decreases when they are in opposite directions. In summary, the main results are as follows: (1) The velocity of the ionic wind at the wall increases with the discharge current and reaches about 3 m/s, (2) the discharge-induced kinetic power increases linearly with the discharge current, (3) the use of the EFD actuator induces a drag reduction of 30% at U 0 = 1 0 m / s , (4) the efficiency of the EFD actuator is rather low in this aerodynamic configuration (a few %) and decreases with the discharge current, (5) the plasma layer must be as thin as possible to have an electrohydrodynamic number greater than one and good efficiency.