Characterization of the transient response of oscillating DBD plasma actuators for turbulent skin-friction control

Controlling near-wall turbulent structures is essential to achieve significant skin-friction drag reduction. Oscillating walls have been shown to reduce friction drag caused by turbulence when actuation is tuned to turbulent time-scales, but reproducing the same flow field without moving surfaces remains a challenge. Plasma actuators based on Dielectric Barrier Discharge (DBD) provide a promising alternative, enabling wall-parallel oscillating flows without mechanical motion. To assess their performance in realistic conditions, actuator geometry and electrical parameters must be optimized for high values of Reynolds number. The CICLoPE Long Pipe facility offers a unique environment for such studies. Here, we present a characterization of the transient response of DBD plasma actuators designed for Reτ > 10, 000. Using Schlieren imaging with high-speed acquisition up to 10, 000 fps, density and temperature fronts induced by plasma actuators have been tracked. A dedicated image-processing algorithm was developed, enabling the study of wall temperature fields induced by the plasma actuator, as well as providing a reliable tracking of the plasma-induced flow and the phase-actuation symmetry.