Characterization of Dielectric Barrier Discharge Plasma Actuators for Drag Reduction

The environmental impact of the aviation sector has prompted significant research efforts aimed at developing strategies to reduce aircraft aerodynamic drag. In particular, it is estimated that 50% of the overall drag for a medium sized civil aircraft is caused by skin friction drag. In order to reduce it, many active and passive flow control techniques are currently being studied and have been employed in recent years. The primary means to achieve drag reduction is to interact with and disrupt the coherent turbulent structures, thus suppressing the regeneration and self-sustaining mechanisms typical of wall-bounded turbulence. One of these active techniques involves the use of dielectric barrier discharge plasma actuators (DBD-PAs). These devices ionize and accelerate the fluid that surrounds the exposed electrode, generating a controlled wall jet flow. They are particularly versatile due to their simple design, low weight and reduced size, as well as their moderate manufacturing cost. In addition, as an active flow control technique, they offer the ability to adapt to a wide range of operating conditions. In this thesis project, different actuator configurations were constructed by varying their shape and geometric parameters. The manufacturing process is innovative, offering higher precision and faster production compared to previously used techniques, and involves the use of a stencil laser-cut into geometries of arbitrary complexity. The DBDs are capable of operating in various modes, such as unidirectional jet, oscillating wall, standing wave, and bidirectional jet configurations. Subsequently, the actuators were characterized with respect to their body force generation and electrical response, as well as power consumption. Finally, the variation in drag was evaluated when the actuators were mounted on a flat plate placed inside an open loop wind tunnel. The experimental measurements were conducted using cross-flow Stereo Particle Image Velocimetry (S-PIV) techniques, while the characterization process was mainly carried out with Pitot tube measurements and direct voltage and current readings obtained from an oscilloscope. All activities were conducted at the Laboratory of Aeronautics "M. Panetti" of Politecnico di Torino.