Strategies for control of transitional and turbulent flows using plasma-based actuators

An exploratory numerical study of the control of transitional and turbulent separated flows by means of dielectric-barrier-discharge (DBD) actuators is presented. The flow fields are simulated employing a high-fidelity Navier–Stokes solver augmented with a phenomenological model representing the plasma-induced body forces imparted by the actuator on the fluid. Several applications are considered, including interaction of an actuator with a laminar boundary layer, suppression of wing stall, control of boundary layer transition on a plate, control of laminar separation over a ramp, and turbulent separation over a wall-mounted hump. Effective suppression of stall over a NACA 0015 airfoil at moderate Reynolds numbers is demonstrated using either co-flow or counter-flow actuators pulsed at a sufficiently high frequency. By contrast, continuous actuation is found to provide little control of separation. For a laminar boundary layer developing along a flat plate, a counter-flow DBD actuator is shown to provide an effective on-demand tripping device. This property is exploited for the suppression of laminar separation over a ramp. Control of turbulent boundary-layer separation over a wall-mounted hump suggests that once the flow is turbulent, control effectiveness is only achieved for higher actuator strengths with implications for the scalability of DBD devices to higher freestream velocities.