Aerodynamics and power requirements of climbing flight in fruit fly model

This study presents a novel numerical investigation, concentrating on the force generation and power consumption associated with climbing flight in fruit flies (Drosophila virilis) across varied climbing angles and advance ratios. The selection of fruit flies as the focal species stems from the availability of comprehensive data on their hovering, ascending, and forward flight. The idealized wing motion employed in the study is completely defined by previously established kinematic parameters, utilizing reasonable assumptions. To address heightened force requirements and counteract negative effects induced by the “downwash flow” inherent in climbing flight, insects must adjust their flapping wing motion. Two potential strategies, involving the augmentation of stroke amplitude and/or elevation of the angle of attack, as observed in experimental studies, were considered. Corresponding simulation cases were subsequently solved using a three-dimensional incompressible Navier-Stokes solver. The study identifies key flow structures and the predominant high lift mechanism, specifically the “delayed stall” of the leading-edge vortex. Analysis of power consumption reveals that insects can only attain a specific range of flight speeds under particular climbing angles, with the maximum speed exhibiting a negative correlation with the climbing angle. Furthermore, power consumption exhibits a gradual increase in the slow speed region, irrespective of the climbing angle. Subsequently, power requirements experience a notable surge upon reaching a climbing-angle-dependent speed threshold. Therefore, the maximum achievable advance ratios are approximately 0.66, 0.49, 0.40, and 0.31 for climbing angles of 0.0°, 22.5°, 45.0°, and 90.0°, respectively.