Surface corona discharge along an insulating flat plate in air applied to electrohydrodynamically airflow control

Abstract

Several studies have shown that a surface corona discharge may be used as an airmoving actuator in order to control the airflow around an obstacle, such as an airfoil to enhance lift or to reduce the drag for example. For some years, our laboratory has been working on this subject, especially in the case of a DC corona discharge. Although efficient aerodynamic effects have been observed, it is sometimes difficult to control the discharge properties. Consequently, the present paper deals with experimental work concerning the electrical properties of a DC surface corona discharge established between two wire electrodes flush mounted on the wall of a PMMA insulating plate. This study shows that (1) Several discharge regimes may be obtained as a function of the applied electric field. (2) When the free airstream flows in the same direction of the ionic wind, the discharge is more stable and its current increases with the airstream velocity U0. (3) When the gas flows in the opposite direction (Uo < 0), the current is quite stable. (4) The discharge current is nearly proportional to E/P where E is the electric field and P the gas pressure. (5) Higher discharge currents may be reached when the negative polarity is applied to the wire electrode with the upper diameter. (6) The discharge current decreases when the air humidity (RH) increases. (7) In a range between +20°C and +65°C, the wall temperature has no influence on the discharge. (8) To obtain a more stable DC corona discharge, one needs U0 high, RH low and the positive polarity must be applied to the wire electrode with the lower diameter.