Effectiveness of synthetic jet actuators for separation control on an airfoil

• Main Author: Dahalan, Md. Nizam
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://eprints.utm.my/id/eprint/79371/1/MdNizamDahalanPFKM2017.pdf; http://eprints.utm.my/id/eprint/79371/

The aerodynamic performance of an airfoil could be improved by controlling flow separation using active flow control techniques. In this study, a synthetic jet actuator (SJA) based on piezoelectric diaphragm has been developed. The selection of the SJA was due to their advantages in being lightweight, no external air supply required, simple system assembly, fast time response, low power consumption, easy installation, low cost and relatively small in size. Basically, the performance of the SJA depends on the specification and configuration of jet orifice, cavity, and oscillating membrane. The parameters studied include waveform signal, frequency, voltage, cavity and orifice physical characteristics. Final design and geometry of the SJA were determined based on these parameters. The SJA design with the best performance has been developed to generate sufficient air jet velocity to control flow separation. The experimental results measured by a hot-wire anemometer show that the maximum jet velocity obtained by the SJA with circular and slot orifice were 41.71 m/s and 35.3 m/s at an applied frequency of 900 Hz and 1570 Hz respectively. Next, the selected SJA was embedded into the wing with NACA 0015 airfoil and placed at 12.5% chord from the leading edge. Wind tunnel testing was conducted for stationary and oscillating airfoil conditions, with and without the SJA. The unsteady aerodynamic loads were calculated from the surface pressure measurements of 30 ports along the wing chord for both upper and lower surfaces. The airfoil was tested at various angles of attack at a free-stream velocity of up to 35 m/s corresponding to a Reynolds number of 1.006 x 106. Specifically for an oscillating airfoil, the reduced frequency, k, was varied from 0.02 to 0.18. The results of an airfoil with SJA showed that the CLmax and stall angle increased up to 13.94% and 29% respectively. Based on the results obtained, the SJA has an excellent capability to control the flow separation with delaying the stall angle, increasing the maximum lift, reducing the drag and delaying the intense nose down pitching moment.