Wind tunnel quantification of dynamic stall on an S817 airfoil and its control using synthetic jet actuators

Abstract

Wind tunnel experiments were performed to quantify the aerodynamic characteristics of the S817 airfoil in dynamic stall conditions, and the subsequent application of active flow control to modify the manner by which dynamic stall incepts. Both quasi‐2D and cantilevered finite span configurations were tested. Surface pressure, six‐component force‐torque sensor, and stereoscopic particle image velocimetry (SPIV) were used to quantify the baseline flow and the benefits of actuating synthetic jets (installed at x/c = 0.35, angled 45° into the flow, and at a momentum coefficient Cμ = 0.012). The airfoil was pitched at reduced frequencies of kf = 0.025 and 0.05 and at shallow and deep stall. Vortex induced lift from dynamic stall was observed and was eliminated by the use of synthetic jets for nearly all conditions; pitching moment deviation was also observed to be significant, and was eliminated at shallow stall and significantly reduced during deep dynamic stall when the synthetic jets were actuated. Moreover, the activation of synthetic jets resulted in significant reduction in the hysteresis (area within the pitching up and pitching down load history) of the lift and pitching moment through all experimental conditions, as much as 41% and 85%, respectively. SPIV flow fields in shallow dynamic stall demonstrated that actuation of synthetic jets confined the separated region to the trailing edge, in both the instantaneous and time averaged sense. To further reduce the lift and pitching moment hysteresis at high angles of attack, a pulse modulation technique was used and showed a marked increase in synthetic jet performance compared with the continuously actuated case and achieved this result with approximately 65% less power consumption.

Aerodynamic and aeroacoustic performance assessment of a vertical axis wind turbine by synergistic effect of blowing and suction

“…The synthetic jet (SJ) strategy (Fig. 3) works mainly via a piezoelectric brake, which generates continuous suction and blowing by vibrating the membrane periodically [28].…”

The influence of oscillating trailing-edge flap on the dynamic stall control of a pitching wind turbine airfoil

“…In wind turbine industry, the everincreasing growth in the size of wind turbine rotors makes the blades be subjected to severe unsteady flows, mostly originating from gusts, tower shadow, yaw error and wind shear and turbulence [4]. Consequently, the implementation of active control techniques in modern wind turbines plays an important role in performance enhancement and extending the life span and a reduction in energy cost of a wind turbine [5].…”

Numerical Investigation of Jet Angle Effect on Airfoil Stall Control

“…Stall suppression with an active flow control technique is of interest in this study. Various active flow control techniques using fluidic actuators have been studied to mitigate flow separation [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Among numerous methods, steady-blowing jet would be the simplest fluidic actuation, ejecting a jet flow continuously into the surrounding.…”