On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

Abstract

Commercial and military aircrafts or miniature aerial vehicles can suffer from massive flow separation when high angles of attack are required. Single dielectric barrier discharge (DBD) actuators have demonstrated their capability of controlling such a separated flow at low external velocity. However, the processes resulting in the improvement of the flight performances remain unclear. In the present study, the reattachment process along the suction side of a NACA 0015 placed at an angle of attack of 16 • is experimentally investigated for an external velocity of 20 m/s (Re = 260,000). A single DBD actuator is mounted at the leading edge of the model. The velocity fields above the suction side of the airfoil are measured by a high-speed acquisition system (3 kHz). The results indicate that the baseline flow presents shed vortices that form at the leading edge and linearly grow along the free shear layer axis. This vortex shedding is organized and exhibits a specific frequency of about 90 Hz. The continuous actuation produces a partial flow reattachment up to 70% of the chord length. Temporal cross-correlation function indicates the presence of a vortex shedding at the trailing edge of the controlled flow. Finally, the temporal analysis demonstrates that the reattachment process requires 50 ms to reach a stabilized attached flow. The time-resolved analysis of the reattachment suggests that the actuation by plasma discharge acts as a catalyser by reinforcing one of the coherent flow structures already existing in the natural flow.

Separation Control on a NACA 0015 Airfoil with Plasma-Actuator-Generated Disturbance

“…At V a = 0 (no control), the airfoil stalls at α = 13° and C Lmax is 0.85. The airfoil experiences a strong adverse pressure gradient at post-stall α, and the separation occurs at the leading-edge region as confirmed by Benard et al [22] at the similar Re. When the straight-edge plasma actuator is deployed, the two-dimensional jet is produced in the direction of the freestream flow, and so, momentum is added to the boundary layer directly, leading to the pressure recovery.…”

A rapidly settled closed-loop control for airfoil aerodynamics based on plasma actuation

“…The airfoil experiences a strong adverse pressure gradient at post-stall α and flow separation occurs between 3 and 6 % airfoil chord from the leading edge. On the other hand, the turbulence intensity grows rapidly in the shear layer, promoting the formation and strength of vortical structures along the shear layer axis (Wu et al 1998;Benard and Moreau 2011).…”

Effect of a filamentary discharge on the particle trajectory in a plane-to-plane DBD precipitator

“…The velocity components are computed using a sequential cross-correlation algorithm with adaptative multipass, interrogation windows of 64×64 to 16×16 pixels and an overlap set to 50 %. More details about the time-resolved PIV technique can be found in [10][11].…”