The Wing and Tail Interactions and Dipole-Jet Formation in Perching Maneuver

Perching is a complex and psychologically risky maneuver involving rapid deceleration, body rotation, and changes in altitude. Yet natural flyers, such as birds, execute this maneuver with remarkable ease. During perching, birds also morph their wing geometry—sweeping the wings backward or forward—and spread their tails, adding further intricacy to the kinematics and enhancing wing–tail aerodynamic interactions. In this study, we investigate these effects using four bird-inspired models with straight and swept-back trailing edges, each tested with and without a tail, while executing a range of pitch-to-deceleration rates. The results reveal that at low pitch-to-deceleration ratios, the straight and swept-back models exhibit similar instantaneous force histories, whereas the addition of a tail increases the maximum lift by approximately 35% compared with tailless configurations. At high pitch-to-deceleration ratios, the swept-back wing generates roughly 30% higher peak lift than the straight wing. Flow-field measurements show that the swept-back wing produces larger and stronger leading-edge vortex (LEV) structures than the straight wing. Vorticity fields also indicate that near the inboard span locations, the interaction between the wing’s trailing-edge vortex and the tail’s LEV contributes to enhanced aerodynamic performance during the perching maneuver.