Active Turbulent Boundary Layer Control: An Experimental Evaluation of Viscous Drag Reduction Using Pulsed-DC Plasma Actuators

Viscous drag reduction in turbulent boundary layers has been an exceptionally interesting topic within fluid dynamics for several decades. The field itself is rich with studies, efforts, failures and successes starting back from the 1950s. That being said, with each attempt, experiment, simulation and trial, the field grows little by little and what is commonly understood today is a result of all the work that has came before. The work presented in this dissertation contributes to the field from two different aspects; the practical application of improving the performance of aerodynamic vehicles and the understanding of complex interactions and dynamic mechanisms that exist withing wall-bounded turbulent flows. A series of experimental drag reduction studies with the utilization of a novel pulsed-DC plasma actuator as the primary means of flow control were conducted. Viscous drag reduction over a flat plate in a zero-pressure gradient boundary layer was achieved over a decade of Mach numbers all while maintaining net power savings. Accompanying flow diagnostics revealed a stabilization and reduction of the spanwise mean flow distortion of the wall-layer as evidenced by a decrease in the activity of the wall streak structure, which plays a significant role in turbulence production and, subsequently, viscous drag.