This paper presents an unsteady discrete vortex model to simulate the unsteady aerodynamics of a wing encountering a large-amplitude transverse gust with a sine-squared velocity profile. The model is used to investigate wing-gust encounters and the impact of closed-loop control on mitigating the gust. A simple proportional closed-loop control law based on pitching input about the wing's midchord is selected to regulate lift during a gust encounter by evaluating its rejection of lift disturbances using Theodorsen's unsteady aerodynamic model. The control law is tested on the discrete vortex model and is shown to reduce the peak lift coefficient of the gust encounter by 92.3% for gust ratio $\text{GR}=V_{\text{max}}/U_{\infty }=0.50$ and by 91.8% for $\text{GR}=1.00$. The flow field and vorticity shedding behavior of the leading edge is studied and the effect of closed-loop control on the circulatory contribution to lift is discussed. The total lift force is decomposed into its individual contributions to study the various mechanisms involved in achieving the lift regulation objective.

• Received 5 February 2020
• Accepted 17 June 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.074701