Experimental study of the aerodynamic interaction between the forewing and hindwing of a beetle-type ornithopter

Beetles have attracted attention from researchers due to their unique combination of a passively flapping forewing and an actively flapping hindwing during flight. Because the wing loads of beetles are larger than the wing loads of other insects, the mechanism of beetle flight is potentially useful for modeling a small aircraft with a large weight. In this paper, we present a beetle-type ornithopter in which the wings are geometrically and kinematically modeled after an actual beetle. Furthermore, the forewing is designed to be changeable between no-wing, flapping-wing, or fixed-wing configurations. Micro-electro-mechanical systems (MEMS) differential pressure sensors were attached to both the forewing and the hindwing to evaluate the aerodynamic performance during flight. Whether the forewing is configured as a flapping wing or a fixed wing, it generated constant positive differential pressure during forward flight, whereas the differential pressure on the hindwing varied with the flapping motion during forward flight. The experimental results suggest that beetles utilize the forewing for effective vertical force enhancement.