Flow Separation Control over an Airfoil with Nanosecond Pulse Driven DBD Plasma Actuators

Abstract

This work continues an ongoing development and use of dielectric barrier discharge (DBD) plasma actuators driven by repetitive nanosecond pulses for high Reynolds number aerodynamic flow control. These actuators are believed to influence the flow via a thermal mechanism which is fundamentally different from the more commonly studied AC-DBD plasmas. Leading edge separation control on an 8-inch chord NACA 0015 airfoil is demonstrated at various post-stall angles of attack (α) for Reynolds numbers (Re) and Mach numbers (M) up to 1.15x10 6 and 0.26 respectively (free stream velocity, U ∞ = 93 m/s). The nanosecond pulse driven DBD can extend the stall angle at low Re by functioning as an active trip. At poststall α, the device generates coherent spanwise vortices that transfer momentum from the freestream to the separated region, thus reattaching the flow. This is observed for all Re and M spanning the speed range of the subsonic tunnel used in this work. The actuator is also integrated into a feedback control system with a stagnation-line-sensing hot film on the airfoil pressure side. A simple on/off type controller that operates based on a threshold of the mean value of the power dissipated by the hot film is developed for this system. A preliminary extremum seeking controller is also investigated for dynamically varying Re. Several challenges typically associated with integration of DBD plasma actuators into a feedback control system have been overcome. The most important of these is the demonstration of control authority at realistic takeoff and landing Re and M. Nomenclature c = model chord, 20.32 cm C L = sectional lift coefficient

Separation Control with Nanosecond-Pulse-Driven Dielectric Barrier Discharge Plasma Actuators

“…This behavior has also been observed on a NACA 0015. 33 Application of the actuator to the leading edge prevents measurements of static pressure in this region as seen in Figure 15a for both a stalled and attached condition. In lieu of ΔC L , the change in C P nearest the leading edge (which correlates with ΔC L ) 34 is employed (Figure 15a).…”

“…This is supported by recent experiments on a NACA 0015 with NS-DBD that indicate optimal F + near 2. 33 Certainly, F + ≈1 provides guidance for selecting forcing frequencies, but is by no means a universal optimum.…”

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

“…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]. Instead of manipulating a flow dynamic, the actuator can be used as a generator of predefined perturbations easily tuned by the applied electrical signal [25].…”

Flow Separation Control near NACA23012 airfoil by a Capacity Coupled Surface HF Discharge

“…The main features observed were a series of vortices, convecting downstream from the leading edge. Series of vortical structures at pulse-periodic discharge operation was obtained by PIV in [13]. Same structures appear at SHFD forcing [14].…”