Effective Mechanisms for Turbulent-separation Control by DBD Plasma Actuator around NACA0015 at Reynolds Number 1,600,000

Abstract

We have conducted large-eddy simulations of turbulent separation flow with control by the DBD plasma actuator over the NACA0015 airfoil. The Reynolds number based on the chord length is 1,600,000 and the angle of attack is 20.11 degs. At this angle of attack, the flow around the airfoil is fully separated. The effects of the location and operating conditions of the plasma actuator on separation control are investigated. The most effective location of the actuator to suppress the separation is the vicinity of the turbulent-separation point (second separation). In the burst mode cases, the most effective non-dimensional burst frequency to improve the lift coefficient is unity. The effective mechanism for the turbulent-separation control by the burst mode is to induce the pairing of the large-scale vortices near the airfoil surface. This large-scale vortex results in not only the momentum induction from the freestream to the boundary layer but also the lift improvement by its convection. In addition, several control effects can be achieved depending on the settings of the DBD plasma actuator. The slight drag improvement can be obtained with shortening the laminar separation bubble through the high frequency actuation from the leading edge.