Numerical investigation of the passive pitching mechanism in odor-tracking flights

It is observed that insects’ foraging flight consists of two distinct flight patterns: surging upwind and zigzagging crosswind. Despite the extensive investigations of the flapping wings, we have limited understanding of how the flight trajectories potentially affect both aerodynamics and physiological sensitivities during an odor-tracking flight. In this paper, we investigated a fruit fly model in both surging upwind and zigzagging crosswind flight trajectories. The flight trajectories were predetermined while the wing flapping motion were simulated using a torsional spring model attached along the wing leading-edge. We simulated the aerodynamic performance and unsteady flow features using an immersed-boundary-method-based computational fluid dynamics solver with fully coupled to equations of motion. The passive wing pitching motion results from the interaction between the wing and surrounding air. For the zigzagging flight, the rest angle is employed to adjust the pitch angle and thus generate sufficient forces and torques to achieve the maneuverability. The aerodynamic performance, wake patterns and odor plume structures are carefully analyzed and compared between two distinct flight patterns. The findings of this work could provide important implications for the future design of flapping-wing micro air vehicles with olfactory sensors onboard.