Active Turbulent Boundary Layer Drag Reduction Using Pulsed-DC DBD Plasma Actuators*

Viscous drag reduction was achieved in zero pressure gradient turbulent boundary layers over a flat plate across a range of Mach numbers. The primary means of flow control was a spanwise array of Pulsed-DC dielectric barrier discharge (DBD) plasma actuators which provided forcing in the sublayer of the boundary layer. Drag was measured directly using a floating force balance mounted on linear air bearings. For flow diagnostics between un-actuated and actuated cases, an electronically isolated, floating constant-temperature hotwire anemometer was developed. Hotwire measurements showed a decrease in both the turbulence intensity and energy in the spectra in the wall-normal profiles. The ``bursting" frequency for un-actuated and actuated cases was measured using the Variable-Interval-Time-Averaging technique (outlined by Blackwelder and Kaplan 1976). A nearly linear correlation between the decrease in viscous drag and the number of ``burst" events was observed.