Study of a DBD plasma actuator dedicated to airflow separation control

Since about ten years, dielectric barrier discharge (DBD) was studied as electro-hydrodynamic (EHD) actuator for airflow control. A DBD surface discharge generates nonthermal plasma allowing to modify the boundary layer of airflow. The active control enables fast action on airflow. A thin flexible asymmetric DBD actuator was used in our study, each elementary DBD was made with two copper electrodes of 35 mum in thickness and 6 mm in width. Dielectric was a multilayer configuration using Kaptonreg and Mylarreg. Two lengths of electrode were used in applications mentioned below: 150 mm and 900 mm. The DBD actuator was characterized by means of electric and optical measurements: discharge currents, voltages and dissipated power of DBD actuator; spectroscopic measurements were also performed. All these measurements were done for several frequencies of power supply. For flow separation controls experiments, firstly, we performed tests on a 1 m length flat plate with an elliptic leading edge placed in an open wind tunnel. This wind tunnel has a test section of a 2 m times 0.5 m times 0.5 m (LtimesHtimesW). Several DBD actuators with 150 mm length electrodes were placed on the upper surface of the flat plate. The action of DBD actuator enables to obtain a more stable laminar boundary layer and to delay the laminar-turbulent transition. Secondly, a 1 m chord and 1.10 m span wing-like airfoil (BMVR130) was used to perform measurements. This airfoil was placed in a wind tunnel whose test section has dimensions of 5 m times 2 m times 2 m. DBD actuators with electrode length of 900 mm were installed on the extrados of profile every 30 mm from x/c = 0.02 to x/c = 0.8. However, only a few elementary DBDs (up to 4) operated simultaneously. The experiments were carried out for velocities up to 15 m/s (Re = 106) and for angles of attack ranging from 8deg to 16deg. Flow visualizations were performed with a PIV system, the drag and lift coefficients were deduced by aerodynamic balance measurements. At 10 m/s (Re = 670,000), the flow was fully reattached for the angles of attack from 8deg to 12deg. A lift increase of about 5% could be observed.