Spatio-Temporal Characteristics of Oscillatory Gas Discharges: Combined and Simultaneous Electro-Optical Diagnostics

The present work addresses the investigation of the spatio-temporal character of dielectric barrier discharge plasma actuator arrays applied to generate virtual wall oscillations. To this end, an electro-optical diagnostics approach is introduced. Optical measurements by means of intensified charge-coupled device imaging are conducted to capture the light emission of the oscillatory gas discharges, allowing observation of the discharge characteristics of the plasma actuator array for individual phase positions within both the oscillation and plasma cycle. Through simultaneous acquisition of electrical signals of the actuator limited to the captured image domain, the entire light emission is directly linked to the ignited surface discharges. On this basis, occurring discharge structures are observed throughout the plasma cycle that can be related to the applied voltage signals. A quasi-linear correlation of the integral discharge light emission and transferred charge is determined. It is shown that the present experimental assessment allows to uncover the spatio-temporal relation of opposing discharge filaments occurring for the present plasma actuator array and forcing strategy, and (as a future scope) their influence on the resulting flow manipulation upon periodically changing forcing direction can be evaluated.