Unsteady Loading of a Wing in Global Streamwise Gusts

Characterizing the aerodynamic response of wings to oncoming gusts is critical to maintaining stability and efficiency of aircraft. In this study, surface pressure and particle image velocimetry measurements are used to analyze the unsteady flow physics of a separated NACA 0015 wing in global streamwise gusts, which impose a time-varying velocity on the wing. Unsteadiness exhibited in the wing's aerodynamic response to velocity acceleration and deceleration can be attributed to the dynamics of developing vortical structures on the suction side. Whether the flow is accelerating or decelerating determines the temporal and spatial scales of the vortical structures, including the convective time, size, and location from which vortical structures develop and shed. These scales determine the degree to which vortical structures interact with each other and with the wing surface, thereby also influencing the unsteady loading on the wing.