Experimental and numerical investigation on the surface charge distribution in a Dielectric Barrier Discharge fluiddynamics plasma actuator.

The Electro-Hydro-Dynamics (EHD) interaction, induced by a dielectric barrier discharge (DBD) in the aerodynamic boundary layer induced in a one atmosphere still air, has been studied both numerically and experimentally. Three different geometrical actuator configurations have been used. The first one is constituted by an electrode pair separated by a 2 mm dielectric teflon sheet. The second and the third configuration have been obtained by adding a third electrode on the upper dielectric surface. This electrode has been placed downstream of the upper electrode and has been connected to the ground or has been left floating. The high voltage electrode has been fed by an a.c. electrical signal. Measurements of the dielectric surface potential generated by the charge deposition have been obtained by using an electrostatic voltmeter. Numerical simulations allowed to determine the charge distribution on the dielectric surface. The discharge has been switched off after positive and negative values of the plasma current. The measurements have been carried out after both phases. Surface potential distributions show that the charge build up takes place several centimeters downstream the upper electrode after the end of the plasma extension. The charge distribution strongly depends on the switching off phase and is heavily affected by the geometrical configuration. Velocity profiles are obtained by using a Pitot probe. They show that the third electrode limits the fluid dynamics performance of the actuator. A relation between the charge surface distribution and the EHD interaction phenomenon has been found. Images of the plasma have been taken to evaluate the discharge structure and the extension of the plasma in the different geometrical configurations studied.