Phasing of dragonfly wings can improve aerodynamic efficiency by removing swirl

摘要: Dragonflies are dramatic, successful aerial predators, notable for their flight agility and endurance. Further, they highly capable of low-speed, hovering even backwards flight. While insects have repeatedly modified or reduced one pair wings, mechanically coupled fore hind dragonflies damselflies maintained distinctive, independently controllable, four-winged form over 300 Myr. Despite efforts at understanding the implications flapping with two pairs previous studies generally painted a rather disappointing picture: interaction between wings reduces lift compared operating in isolation. Here, we demonstrate mechanical model dragonfly that, despite presenting no advantage terms lift, flying can be effective improving aerodynamic efficiency. This is achieved by recovering energy from wake wasted as swirl manner analogous to coaxial contra-rotating helicopter rotors. With appropriate fore–hind wing phasing, power requirements up 22 per cent single indicating that may apply both and, future, biomimetic micro air vehicles.