An unsteady aerodynamic force calculation method for shear variable-sweep wing considering sweep angle and airfoil changes

The backward shift of the aerodynamic center and insufficient morphing capability are critical design bottlenecks of traditional rotary variable-sweep wings. This paper presents a new shear variable-sweep morphing form that reduces the backward shift of the aerodynamic center by allowing the leading edge of the wing to slide forward. The shear variable-sweep wing (SVSW) with this morphing form enables coordinated changes in both planform and airfoil shape, achieving greater aerodynamic benefits. However, during the shear morphing process, the wing experiences unsteady aerodynamic phenomena, and this multi-dimensional morphing form further complicates the calculation of unsteady aerodynamic forces. To address this challenge, this paper investigates the three-dimensional changes of the SVSW surface during the shear morphing process and proposes an unsteady aerodynamic force calculation method, which considers variations in sweep angle and airfoil. The results showed that as the sweep angle increases, both the lift and drag coefficients decrease, and the unsteady aerodynamic characteristics exhibit significant flow hysteresis, with the unsteady lift and drag coefficients deviating from the steady-state results and forming a clockwise dynamic hysteresis loop. Finally, the study analyzed the effects of shear morphing rates and flow conditions on the wing's unsteady aerodynamic characteristics and validated the feasibility and effectiveness of the proposed method through continuous morphing wind tunnel tests. The proposed method also fully considers the effects of shear motion, curved aerodynamic configurations, and unsteady vortices on aerodynamic characteristics, offering a low-cost and effective solution for the optimization design and aeroelastic analysis of the SVSW.