Longitudinal free flight of a model insect flyer at low Reynolds number

This paper is concerned with the numerical simulation of the free longitudinal flight of a low Reynolds number flapping-wing flyer, modelled after the fruit-fly Drosophila melanogaster. In the numerical model, the computational fluid dynamics governed by the Navier-Stokes equations and 6-DoF Newtonian dynamics of the flyer in a gravity field are integrated with active adaption of its wing kinematics. The latter comprises sweeping, elevating and feathering related actions of insect wings during flight that have been observed and identified by biologists. These actions are modulated during flight by a generic control algorithm to produce sustained stable quasi-steady free flight for speeds of up to 80 cm/s (J = 0.28) in forward and −20 cm/s in reverse flight. The dynamics of longitudinal flight elicited in the present study are consistent the observations and analyses of biologists, but provide detailed information and access to a more complete picture of the coupled constituent dynamics of fluid and flyer in free flight condition than is currently available in the literature. The present free flight model offers a prospective line of inquiry that could complement existing experiments with live insect subjects in a wider study of 'real-time' dynamics of insect flight and manoeuvres. The work may also be relevant to the development of biomimetic mechanical flapping-wing flyers.