Friction Drag Reduction Mechanism Under DBD Plasma Control

Abstract

This work aims to understand the mechanism behind friction drag reduction in a dielectric barrier discharge (DBD)-plasma-controlled flat-plate turbulent boundary layer (TBL). Streamwise-oriented DBD plasma actuators are deployed to generate streamwise counter-rotating vortices in the TBL. The variation in the local friction drag is measured using a single hotwire, and the change in the flow structure is captured using a high-speed PIV. At a voltage V _a of only 4.25 kV, the drag reduction over an area (90 mm long and 200 mm wide) behind the plasma actuators reaches 14%. In fact, the drag reduction area stretches longitudinally to about 300 mm or 2000 wall units. The drag reduction is found to be linked to the decrease in the near-wall turbulent kinetic energy production, pointing to that the plasma-actuator-generated streamwise vortices interrupt effectively the turbulence generation cycle, thus stabilizing near-wall velocity streaks and resulting in friction drag reduction.