Drop impact behavior and wall adaptive deflection response of cantilevered dragonfly wings

The behavior of drop impact and the adaptive deflection response of cantilevered dragonfly wings to the wall are investigated through both experimental and theoretical studies. In addition, the directional transport behavior of the drop interface and the wall deflection response characteristics of the lightweight surface during drop impact are analyzed. Results show that the drop undergoes unidirectional transport after impacting the cantilevered dragonfly wings. During the impact phase, the drop bulge takes on a straw-hat shape, the drop forms an elongated shape during the spreading phase, and the dragonfly wings recover after reaching maximum tip deflection. Based on the Euler-Bernoulli beam theory, the inertial scenario improvement model, and the kinetic energy theorem, a deflection response model of the drop affecting the wall is established, and the proportional constant is taken according to the experimental result. Analysis shows that the drop transport time, the dragonfly wing deformation, and the energy increase with the increase of impact height. The actual tip deflection first decreases and then increases with We. The actual value is lower than the theoretical value over part of the 20 and 25 mm ranges but remains higher at 30 mm. The theoretical transport time is less than the actual one. The maximum deformation energy of the cantilevered dragonfly wing increases from 5.2 × 10^-5 µJ to 1.379 × 10^-4 µJ with increasing height. Due to the fluid-structure interaction, the potential energy of the drop promotes the adaptive deformation and downward movement of the sample, and the elastic energy of the dragonfly wings is released because of the springboard effect.