High-speed imaging and modeling study on the aerodynamic behaviors during takeoff of butterfly forewing, Papilio xuthus

Abstract Butterflies are excellent fliers in nature, flapping mode, which can ensure the completion of complex flight movements, including rapid turns, hovering, and forward and backward flights. In this paper, the Chinese yellow swallowtail ( Papilio xuthus ) was chosen as the bionic research subject. The flapping motion and trajectory function of P. xuthus during takeoff were obtained by the high-speed camera. On this basis, a finite element model of butterfly forewings was established, the flapping trajectory function was imported, and the transient takeoff motion of forewing was simulated by Ansys Fluent 2021R2. The aerodynamic characteristics at different angles of attack during the takeoff were obtained. The flow structure characteristics of the forewing of P. xuthus were analyzed by SIMULIA XFlow 2020. It shows that the lift and drag coefficient of the forewings during takeoff both exhibit a trend of increasing first and then decreasing as the angle of attack increases. The maximum average lift-to-drag ratio is achieved, when the angle of attack is 20°. The obtained wingtip trajectory, optimal angle of attack, and vorticity parameters can provide new design ideas for solving problems such as insufficient takeoff capability and difficult mode switching of flapping-wing microair vehicles design.