Dynamic Flow Control over Aerodynamic Bodies using Phased Array Vectored Synthetic Jet Actuation

Abstract

An experimental investigation into the flow control capabilities of synthetic jet actuators (SJAs) was performed. An array consisting of two synthetic jet actuators was designed and fabricated. The effects of vectoring an array on streamline location and pressure distribution were studied using Particle Image Velocimetry (PIV) and static pressure measurements. Three different bodies were tested: a flat plate, a two-dimensional cylinder representative of a bluff body, and a modified two-dimensional NACA 0018 airfoil representative of a streamlined body. Actuation was performed at Array Momentum Coefficient (Cµ) values ranging from 0.8% to 8%. The relative phase of operation, ϕ, of the individual actuators in the array was varied to control the direction of the jet trajectory. PIV was used to study the streamline deflection pattern over a flat plate. A significant change in streamline deflection pattern was observed in response to changing the phase. For the case of the cylinder, actuator arrays were placed at +/-70° locations with respect to the free stream direction. Actuation was performed at a momentum coefficient value of approximately 0.8% and the phase was varied. Pressure measurements were made over the surface of the cylinder. A 10% decrease in pressure drag was observed for specific cases of phasing. Pressure measurements indicated that the point of separation, in response to actuation at this specific phase angle, was delayed by approximately 20°. An array of actuators was also embedded in a modified NACA 0018 airfoil subjected to a low speed cross-flow. The pressure coefficient (CP) was calculated over the surface. For this case, vectored actuation resulted in a reduction in pressure drag and a simultaneous increase in lift. The benefits of phased actuation over different types of aerodynamic bodies are demonstrated and analyzed using different experimental methods. Nomenclature φ = Operating phase difference between array actuators 1 and 2 b = Streamwise dimension of orifice (width) c = Characteristic Length Scale (used for calculating Cμ and F*) Cμ = Actuator/Array Momentum Coefficient (2bUJ 2 / cU 2 ) CD = Drag coefficient CL = Section Lift coefficient

Potential application of using vortex ring for personalized ventilation

“…Meanwhile, the synthetic jet actuator is usually small in scale, and the formed vortex ring has a high turbulence, moves at a faster velocity, and has a smaller volume. As such, these systems are widely used for drag reduction, heat transfer enhancement, and mixing control 31–34 . In VRPVs, owing to the need for a large air supply distance and ventilation flow rate, the formed vortex ring should have a considerable velocity and volume.…”

“…As such, these systems are widely used for drag reduction, heat transfer enhancement, and mixing control. [31][32][33][34] In VRPVs, owing to the need for a large air supply distance and ventilation flow rate, the formed vortex ring should have a considerable velocity and volume. Therefore, in view of characteristics of (a) and (b), this study proposes a vortex ring generator that uses a pneumatic device to drive a piston.…”

Dye Visualization of In-Line Twin Synthetic Jets in Crossflows—A Parametric Study

“…In real world applications, it is SJ arrays that are usually implemented instead of single SJs. Using two slot SJ actuators, Hasnain et al [19] found that the point of flow separation on a two-dimensional (2D) cylinder can be delayed by 20% at specific phase difference between the two actuators. Zhao et al [20] confirmed that two slot SJ actuators generally have better performances than single SJ in delaying flow separation on a 2D airfoil.…”