High Mach Number Leading-Edge Flow Separation Control Using AC DBD Plasma Actuators

Abstract

Wind tunnel experiments were conducted to quantify the e↵ectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy e cient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the e↵ect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted at the University of Notre Dame Mach 0.6 Wind Tunnel for a range of Mach numbers between 0.1 and 0.4 with an airfoil model of chord 30.48 cm at atmospheric conditions corresponding to a Reynolds number range of 560, 000 through 2, 260, 000. Lift and drag forces, as well as the quarter chord moments were measured directly by a sting which reacted on load cells and torque sensors on the outside of the 0.91⇥0.91 m wind tunnel test section. Two leading-edges of the airfoil were fabricated. The first was covered in a Kapton dielectric film of 0.127 mm and had a 7 µm copper electrode, and the second was a thick-dielectric Macor with a copper tape exposed (76 µm thick) electrode. A high voltage AC signal was applied to electrodes for the flow control case. The results show that the plasma actuators were e↵ective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coe cient and stall angle. In the post stalled regime, the lift was dramatically increased, by as much as 90%. Drag in the stalled regime was reduced by as much as 28% and the nose down pitching moment was reduced by as much as 40%. Pressure taps on the suction surface confirmed flow reattachment as evidenced by the return of a pressure peak near the leading-edge and better pressure recovery aft of the leading-edge when the active flow control was enabled. Time-averaged PIV confirmed the airflow following the airfoil surface closely. The experiment also showed that lift was increased the most in deep stall when the plasma actuator was operated unsteady with a reduced frequency of unity, whereas in light stall steady operation was preferred. Overall, both AC DBD plasma actuator designs were able to increase the maximum lift coe cient and stall angle of attack for the full range of Mach numbers, with the thick-dielectric Macor leading-edge performing better at Mach 0.4.

Dynamics of Rapid Localized Heating in Nanosecond Pulse Discharges for High Speed Flow Control

“…[6] detected compression waves in quiescent air generated by localized heating in the nanosecond pulse discharge in the DBD actuator. Recently, flow separation control by AC DBD plasma actuators has also been demonstrated in high-speed flows (M=0.1-0.4), achieved by increasing peak AC voltage and dielectric thickness [7]. However, determining whether the actuator effect on the flow in these experiments is caused by EHD body force or by localized heating in the plasma remains an open question.…”

Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control

“…1 3 manipulate the dynamics of different flows, such as separated flows (Corke and Post 2005;Little and Samimy 2010;McLaughlin et al 2006;Kelley et al 2012;Jukes and Choi 2009), developing shear layers (Sosa et al 2009a;Benard et al 2008;Thomas et al 2008) or boundary layer laminar-to-turbulent transitions (Joussot et al 2010;Grundmann and Tropea 2007;Hanson et al 2010). In most of these papers, the actuator is used in context of open-loop control, but plasma discharges find a new route in the construction of closed-loop strategies by using DBD (Lombardi et al 2012;Rethmel et al 2011;Grundmann and Tropea 2008;Kriegseis et al 2011a).…”

EHD Force and Electric Wind Produced by Plasma Actuators Used for Airflow Control

“…(9) At the discharge initiation, a starting vortex is created. (10) The time evolution of the body force is strongly unsteady with peak values 10 times higher than its timeaveraged value. (11) The local maximum force can reach about 10 4 N/m 3 .…”

“…Ionization, recombination, attachment, detachment and photo-ionization of charged species occur at time scales of about a few picoseconds [5] and subsequently the produced body force, despite being low pass filtered by fluid mechanical laws (viscosity, energy exchanges, dissipation,…), has a high bandwidth. Plasma actuators, and more specifically dielectric barrier discharge actuators, have demonstrated their authority to manipulate fundamental flow dynamics such as separated flows [6,7,8,9,10,11], developing shear layers [12,13,14,15] or boundary layer laminar-to-turbulent transitions [16,17,18]. In most of these papers, the actuator is used in context of open-loop control but plasma discharges find a new route in the construction of closed-loop strategies by using DBD [19,20,21,22,23,24].…”