On Progress in Exploring Controlled Viscous Limit-Cycle Oscillations in Modified Glauert Airfoil

The paper reports on the progress in the development of a novel robust, nonlinear flow control technology that employs an array of synthetic-jet actuators (SJAs) embedded in 2-DOF, elastically mounted, optimized Modified Glauert (MG) airfoil design in order to control limit cycle oscillations (LCO) at low subsonic flow regimes. The focus here is on the conceptual design of the wind energy harvesting system that employs, e.g., a piezoelectric device to extract energy from plunging LCO, with the closed-loop controller being capable to sustain the required LCO amplitudes over a wide range of wind speeds. The current high-fidelity studies first include validation of the static-airfoil aerodynamic predictions against results obtained from the concurrent experimental campaign. Next, a set of parametric 1-DOF and 2-DOF numerical analyses examine open-loop and closed-loop LCO control strategies that employ the ability of MG airfoil to sustain LCO at subcritical velocities due to natural separation-induced flutter.