Flow control consists of manipulating flows in an effective and robust manner to improve the global performances of transport systems or industrial processes. Plasma technologies, and particularly surface dielectric barrier discharge (DBD), can be a good candidate for such purpose. The present experimental study focuses on optical and electrical characterization of plasma sheet formed by applying a pulse of voltage with rising and falling periods of 50 ns for a typical surface DBD geometry. Positive and negative polarities are compared in terms of current behavior, deposited energy, fast-imaging of the plasma propagation, and resulting modifications of the surrounding medium by using shadowgraphy acquisitions. Positive and negative pulses of voltage produce streamers and corona type plasma, respectively. Both of them result in the production of a localized pressure wave propagating in the air with a speed maintained at 343 m/s (measurements at room temperature of 20 °C). This suggests that the produced pressure wave can be considered as a propagating sound wave. The intensity of the pressure wave is directly connected to the dissipated energy at the dielectric wall with a linear increase with the applied voltage amplitude and a strong dependence toward the rising time. At constant voltage amplitude, the pressure wave is reinforced by using a positive pulse. The present investigation also reveals that rising and decaying periods of a single pulse of voltage result in two distinct pressure waves. As a result, superposition or successive pressure wave can be produced by adjusting the width of the pulse.

This experimental work deals with active airflow control using non-thermal surface plasma actuators in the case of a rectangular cross section turbulent jet. A wide-angle diffuser composed of two adjustable hinged baseplates is linked at the jet exit. Two types of actuators are considered: the DC corona discharge and the dielectric barrier discharge (DBD). In both cases, an ionic wind with a velocity of several m s−1 is generated tangentially to the wall surface. Thus, this induced aerodynamic effect is applied in order to create the separation along the lower hinged baseplate. The effects of both actuators on the flow separation are measured by means of particle image velocimetry for velocity up to 30 m s−1. The main results show that the DBD seems more efficient than the DC corona discharge but the effect decreases with the jet velocity. However, in increasing the discharge frequency up to 1500 Hz, it is possible to separate a 30 m s−1 jet. Finally, by reducing the actuators' length in the spanwise direction, results lead to a visualization of the three-dimensional effects on the separation along the lower hinged baseplate.