Airflow Reattachment Along a NACA 0015 Airfoil by Surfaces Dielectric Barrier Discharge Actuator: Time-Resolved Particle Image Velocimetry Investigation

Abstract

By manipulating the stall regime occurring above the airfoil of aircrafts at high angle of attack, the taking-off and landing phase might be t imely reduced, avoiding extensive fuel consumption and noise radiation. Plasma actuators are suitable and effective active control devices to control such separation of low velocity airflows. However, these control devices require new investigations to be used at velocity c orresponding to real flight conditions. The first step consists of better understanding the dyn amic of the flow control to identify the parameters which can be enhanced. The present study proposes a time-resolved analysis of the flow over a NACA 0015 airfoil by a high-speed P IV system. The airfoil is placed in poststall regime, at an angle of attack of 16°, and a f reestream velocity set to 20 m/s (Re=2.6x10 5 ). An actuator based on a dielectric barrier discharge is mounted at the leading edge and quasi-steady or unsteady actuations are studied. The effects of the quasi-steady actuation, the excitation frequency and the duty-cycle of the unsteady actuation on the time-averaged and the instantaneous velocity fields are presented . The natural vortex street issuing from the flow separation is described and the interactiv e mechanism between the natural vortices and the electric wind produced by the plasma actuat or is proposed and commented. The results demonstrate that the effectiveness of the D BD actuation depends on the used frequency and duty-cycle. The high repetition rate of the acquisition system allows to propose a scenario of the control of the separated flow by a plasma actuation. It appears that the flow reattachment results from a vortex dynamic enhanced by the local airflow produced by the DBD actuator.