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Sebastian D. Goodfellow
Department of Mechanical and Industrial Engineering University of Toronto 5 King's College Road, Toronto, ON, Canada M5S 3G8

Serhiy Yarusevych
Mechanical and Mechatronics Eng. University of Waterloo 200 University Avenue West Waterloo, Ontario, N2L 3G1 Canada

Pierre E. Sullivan
Mechanical and Industrial Eng. University of Toronto Toronto, Ontario, M5S 3G8, Canada


The influence of periodic excitation from synthetic jet actuators, SJA, on boundary layer separation and reattachment over a NACA 0025 airfoil at a low Reynolds number is studied. All experiments were performed in a low-turbulence recirculating wind tunnel at a Reynolds number of 100,000 and angle of attack of α = 5°. Mounted below the surface of the airfoil, the SJA consists of four (32.77mm diameter) piezoelectric ceramic diaphragms positioned in a single row. Initial flow visualization and hot−wire tests were conducted in quiescent environmental conditions to characterize the exit flow from the SJA. Flow visualization results showed a vertical jet pulse accompanied by two counter rotating vortices being produced at the exit of the simulated slot, with the vortices shed at the excitation frequency. Hot-wire measurements determined the maximum jet velocity for a range of excitation frequencies (fe = 50Hz - 2.7kHz) and voltages (Vapp = 50 − 300Vp−p), which were used to characterize the excitation amplitude in terms of the momentum coefficient (Cµ). With the SJA installed in the airfoil, flow visualization results showed a reattachment of the boundary layer and a significant reduction in wake width. Wake velocity profiles were obtained two chord lengths downstream of the trailing edge to assess the excitation effect on drag and wake characteristics. A spectral analysis was conducted in the wake region and showed the presence of vortex shedding at a frequency of 22 Hz. When excitation was applied at 935 Hz and 250 Vp−p, the shedding frequency shifted to 50Hz. The results suggest it is possible to get substantial improvement in airfoil performance at lower input power.