Vortex trapping recaptures energy in flying fruit flies

Fritz-Olaf Lehmann,Thomas Engels,Hao Wang

doi:10.1038/s41598-021-86359-z

Abstract

Flapping flight is one of the most costly forms of locomotion in animals. To limit energetic expenditures, flying insects thus developed multiple strategies. An effective mechanism to reduce flight power expenditures is the harvesting of kinetic energy from motion of the surrounding air. We here show an unusual mechanism of energy harvesting in an insect that recaptures the rotational energy of air vortices. The mechanism requires pronounced chordwise wing bending during which the wing surface momentary traps the vortex and transfers its kinetic energy to the wing within less than a millisecond. Numerical and robotic controls show that the decrease in vortex strength is minimal without the nearby wing surface. The measured energy recycling might slightly reduce the power requirements needed for body weight support in flight, lowering the flight costs in animals flying at elevated power demands. An increase in flight efficiency improves flight during aversive manoeuvring in response to predation and long-distance migration, and thus factors that determine the worldwide abundance and distribution of insect populations.

Highlights

Flapping flight is one of the most costly forms of locomotion in animals
The majority of muscle energy during flight appears as kinetic energy in the surrounding air but part of it is stored as elastic potential energy in the muscle tissue[9], as elastic deformations of the thorax[10] and w ings[11], and as kinetic energy in the movement of wings
This study identifies that the 1.3 mg fruit fly Drosophila virilis harvests energy from trapped vortices during clap-and-fling wing k inematics[27,30,31,32,33,34], at which the flapping wings physically touch and chordwise bend during the dorsal stroke reversal (Fig. 1)

Summary

Introduction

Flapping flight is one of the most costly forms of locomotion in animals. To limit energetic expenditures, flying insects developed multiple strategies. This study identifies that the 1.3 mg fruit fly Drosophila virilis harvests energy from trapped vortices during clap-and-fling wing k inematics[27,30,31,32,33,34], at which the flapping wings physically touch and chordwise bend during the dorsal stroke reversal (Fig. 1).

Results

Conclusion