An Experimental Study on Active Flow Control Using Synthetic Jet Actuators over S809 Airfoil

Abstract

Abstract. This study investigates the effect of periodic excitation from individually controlled synthetic jet actuators on the dynamics of the flow within the separation and re-attachment regions of the boundary layer over the suction surface of a 2D model wing that has S809 airfoil profile. Experiments are performed in METUWIND's C3 open-loop suction type wind tunnel that has a 1 m x 1 m cross-section test section. The synthetic jet array on the wing consists of three individually controlled actuators driven by piezoelectric diaphragms located at 28% chord location near the mid-span of the wing. In the first part of the study, surface pressure, Constant Temperature Anemometry (CTA) and Particle Image Velocimetry (PIV) measurements are performed over the suction surface of the airfoil to determine the size and characteristics of the separated shear layer and the re-attachment region, i.e. the laminar separation bubble, at 2.3x105 Reynolds number at zero angle of attack and with no flow control as a baseline case. For the controlled case, CTA measurements are carried out under the same inlet conditions at various streamwise locations along the suction surface of the airfoil to investigate the effect of the synthetic jet on the boundary layer properties. During the controlled case experiments, the synthetic jet actuators are driven with a sinusoidal frequency of 1.45 kHz and 300Vp-p. Results of this study show that periodic excitation from the synthetic jet actuators eliminates the laminar separation bubble formed over the suction surface of the airfoil at 2.3x105 Reynolds number at zero angle of attack.

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

“…High voltage of a high frequency weakly ionises the surrounding fluid, producing plasma [18,19]. [46] 2016 Speakers 47,000 Max 5% reduction in drag, controlled vortices [47] 2016 Piezoelectric diaphragms Separation control [48] 2016 Synthetic jet UAV Increased lift-to-drag ratio [49] 2016 Synthetic jet AC 840,000 Max 15.8% reduction in total pressure loss, reduced corner separation [23] 2016 Synthetic jet Gas turbines 840,000 Reduced corner vortices, 17% reduction in total pressure loss [50] 2016 Synthetic jet UAV 2,128,000 Controlled vortices [51] 2015 Synthetic jet 896,000 Max 15% reduction in drag and 73% increase in lift, eliminated separation [51] 2015 Synthetic jet 840,000 Max 20.32% reduction in total pressure loss, reduced secondary flow [52] 2014 Speakers Wind turbine 550,000 Increased lift [53] 2014 Piezoelectric diaphragms Wind turbine 230,000 Eliminated separation [54] 2013 Piezoelectric diaphragms UAV 100,000 Induced reattachment, max. 66% reduction in drag [55] 2010 Acoustic perturbations Max 35% increase in plenum pressure [56] 2010 Piezofluidic actuator Wind turbine 70,000-800,000 5-15% increase in efficiency, doubled maximum lift Outcome: Controlled separation, induced reattachment Table 5.…”

Horizontal Axis Wind Turbine Blade Design Methodologies for Efficiency Enhancement—A Review

“…Active flow control (AFC) techniques, on the other hand, can be applied to all types of flow conditions. They are also used to control the boundary layer separation and transition characteristics Bons et al [86] and Gul et al [87]. Aramendia et al [88,89] provided a comprehensive overview about available knowledge, references and investigations on the active and passive flow control devices, initially developed for aeronautic industry which are currently being investigated and used in wind turbine industry.…”

“…They also found out that the tip vortices near the blade were pushed out due to this injection. Another way of using AFC technique is by employing an array of synthetic jet actuators which can be mounted over the suction surface of the blade near the mid-span, as can be seen in Figure 7, which can be periodically excited, Gul et al [87]. The laminar boundary layer on S809 airfoil blade was analyzed experimentally at zero attack angle, demonstrating that the separation bubble covers 19.6% of the chord length and a flow control technique is required to reduce the losses occurring due to separation, Abdulrahim et al [90].…”

“…They also found out that the tip vortices near the blade were pushed out due to this injection. Another way of using AFC technique is by employing an array of synthetic jet actuators which can be mounted over the suction surface of the blade near the mid-span, as can be seen in Figure 7, which can be periodically excited, Gul et al [87]. Sutherland et al [92] reported on the use of two nondestructive acoustic emission and coherent optical testing techniques to monitor the behavior of wind turbine blades during a quasi-static test-to-failure.…”

Aerodynamic Numerical Testing of Megawatt Wind Turbine Blade to Find Optimum Angle of Attack

“…The results of aerodynamic simulations of the steady low-speed flow past two-dimensional Sseries wind-turbine-blade profiles, developed by the National Renewable Energy Laboratory (NREL), are conducted and optimum blade profile for each wind speed was decided based on the maximum lift to drag ratio [1]. Effect of periodic excitation from individually checked synthetic jet actuators on the dynamics of the flow within the separation and re-attachment regions of the boundary layer over the suction surface of a 2D model wing was researched for S809 airfoil profile [2]. Results indicates that periodic stimulation from the synthetic jet actuators fulfills the laminar separation bubble shaped over the suction surface of the airfoil at Reynolds numbers of 2.3x105 at zero angle of attack.…”