Time Variations of Aerodynamic Forces in a Wing Encountering a Wind Gust

Integrating a wind gust generator into the University of Arizona's subsonic wind tunnel allows for the study of aerodynamics and flow around wings and other experimental subjects under unsteady atmospheric conditions. The system comprises a dual-vane gust generator, drivetrain with control module, constant temperature anemometry, and force balance. Two geometrically identical experimental NACA0012 wing models were investigated, made from aluminum alloy 2024 and plastic PLA. This study examines the response of a wing model encountering discrete 1-cos wind gusts across various parameters. The time variations of aerodynamic forces were measured at the freestream velocity 20 m/s and two wing installation angles of 8 and 10 deg. The lift coefficient follows the steady-state trend while exhibiting an unsteady hysteresis loop with a figure-eight shape. Notably, at an installation angle of 10 deg, the maximum lift coefficient is 27% greater than the steady-state value and occurs at an angle of attack 2 degrees higher. The lift coefficients for the PLA wing are higher than those for the aluminum wing, while the lift amplitude remains nearly the same. Flow visualization experiments were performed on the PLA wing by using hot-wire smoke. When a gust encounters the wing, an initial leading-edge vortex is formed. As the peak of the gust gets closer to the leading edge, more vortices continue to form, and previous vortices travel down the wing towards the trailing edge. These vortices keep the flow attached during higher angles of attack.