DEVELOPMENT OF DIELECTRIC BARRIER DISCHARGE ACTUATORS ARRAYS FOR BOUNDARY LAYER STREAKS PRODUCTION

The presented work consists in the development of dielectric barrier discharge (DBD) plasma actuators arrays for introducing streaks in a laminar boundary layer. A single DBD plasma actuator is composed of two electrodes separated by a dielectric layer: one electrode is supplied with a high voltage waveform and exposed to the surrounding flow and the other is grounded and completely covered by an insulating material. Under operation, an electric field is created and the surrounding air is weakly ionized. It results in a net body force that acts on the ambient (neutrally charged) air, inducing a flow jet of few m/s. Different geometrical arrangements can be adopted, each one aiming to a characteristic active flow control application. Spanwise arrays of symmetric plasma actuatorsi can be used for the purpose of generating spanwiseperiodic counter-rotating vortices. A typical application regards the stabilization of a laminar boundary layer to delay transition. In Hanson et al. ii and Grundman et al.iii,iv these dispositives were then used for attenuating the velocity streaks inherent to bypass transition, by superimposing a disturbance of the opposite sense. In Osmokrovic et al.i the influence the of excitation parameters, electrode geometry and dielectric thicknesses on the induced velocity streaks was tested. Moreover, the effect of the actuator length L, spanwise spacing Δz and some operating parameters, like the free stream velocity U∞, are still not well understood. A dedicated activity was devoted for the design and fabrication of different array geometries. They will be then tested in different test conditions (applied voltage amplitude, frequency and free stream velocity).