Aerodynamic investigation and modeling of dynamic variable sweep wing at low Reynolds number

This study investigates the unsteady aerodynamic characteristics of a dynamic variable sweep wing at low Reynolds numbers of 104, with a focus on the effects of variable sweep reduced frequency k on lift generation and flow structures. Numerical simulations reveal two distinct regimes: (1) when k < 0.2, the average lift of dynamic variable sweep cases closely matches with static values, and the flow structure is dominated by the tip vortices and unsteady leading-edge vortices (LEVs) shedding; (2) when k > 0.2, the average lift exceeds the static counterpart and increases rapidly, the LEVs develop into an arch vortex or vortex ring due to the high reduced frequency. Vorticity transport analysis further demonstrates the critical influence of spanwise vorticity transport on LEVs stability and lift generation, providing insights into the aerodynamic mechanisms underlying variable sweep motions. Additionally, a lift predictive model combining Greenberg and Atassi's theories with a correction term shows strong consistency with computational fluid dynamics results within certain frequency ranges. These findings underscore the significant impact of LEVs on lift dynamics and provide valuable insights for the development of bio-inspired aircraft designs.