Numerical study on wake vortex characteristics and aerodynamic benefits of large aircraft in formation flight

Vortex surfing formation flight, a bioinspired lift enhancement and drag reduction technique, holds potential for reducing fuel consumption and extending range, serving as a critical pathway for aviation sustainability. However, its engineering application faces challenges due to the flight-state-dependent evolution of lead aircraft wake vortices and their strong coupling with formation parameters. This study investigates wake vortex evolution characteristics and aerodynamic benefit optimization for large wide-body aircraft (CHN-T2 standard model) at various angles of attack (0°, 1.71°, 3.5°) using Reynolds-averaged Navier-Stokes (RANS) simulations with SST k-ω turbulence model. The results show that the angle of attack significantly affects the wake-vortex evolution mechanism. Compared with the 0° case, at 1.71°, the wingtip vortex rolls up at a more upstream position, and its downward motion is enhanced. At 3.5°, a spatially asymmetric twin-vortex system is induced to co-rotate counterclockwise, and the inboard vortex gradually dominates in the far field. Based on the computational fluid dynamics (CFD) results and the wake-vortex dynamics, an optimal two-aircraft formation configuration, namely "wingtip-overlap and co-altitude" is proposed. This configuration yields a 6.26%–19.8% improvement in the lift-to-drag ratio of the trailing aircraft. The wake-vortex interference risk of the inboard formation configuration is also systematically evaluated. A decay law of the trailing aircraft's lateral-directional stability with increasing angle of attack is obtained. These findings provide critical parametric support for the engineering application of formation vortex surfing flight.