The Importance of Morphology in Further Unraveling the Bumblebee Flight Paradox

Abstract

The size of a bumblebee relative to its wing-span would suggest that flight is not possible according to the conventional aerodynamic theories, yet nature shows that not to be true. Bumblebee wings have venations that create corrugations, with their forewing and hindwing connected with a hook-like structure, known as hamulus. Previous investigations of bumblebee flight modeled wings as smooth surfaces or neglected their accurate morphological representation of corrugation or used a simplified body. To address these shortcomings, the current work explores the significance of vein corrugation and body on lift and thrust, and morphological importance of hindwing and forewing in flapping flight. Computational fluid dynamics simulations were used to analyze an anatomically accurate bee wing and body for hovering and forward speeds. Flow analysis of corrugated and smooth wing models revealed that corrugation significantly enhanced lift by 14%. With increasing speed, the hindwing increased lift from 14% to 38% due to the combined camber created by the forewing and hindwing. A notable feature was that the LEV did not change in size when the hindwing was removed, therefore forewing pressure remained the same as when coupled with hindwing during downstroke. When the bee body was included, the pressure decreased locally between the wing root to 25% of the wingspan on the dorsal side, causing lift for the corrugated model to increase by 11%. The study demonstrates importance of accurately modeling wing corrugation and bee body in flapping flight aerodynamics to unravel the true load-lifting capacity of bumblebees.

Physiological and Environmental Impact of Temperature Change on Bumblebee Flight

“…They inhabit cold and hot environments and are key species for pollinating wild herbs, crops, and vegetables. Unlike honeybees and other bee species, they forage at lower ambient temperatures and for long hours, carry pollen that is nearly 80% percent of their body weight, and are agile fliers that make complex maneuvers [5,11].…”

“…The bumblebee wing is comprised of veins and cells (Figure 1(a)), and the shape of the wing differs among bumblebee species. Also, their wings are small and require rapid beats to keep them aloft [5,18,24]. Corrugated wings (Figure 1(b)) contribute to the aerodynamic performance and flight stability of the bees [25,26].…”

“…Corrugated wings (Figure 1(b)) contribute to the aerodynamic performance and flight stability of the bees [25,26]. It helps larger LEV formation during the downstroke, thus leading to lift augmentation by extending suction pressure on the wing dorsal side [5].…”

“…Their results showed that the wing corrugation is a critical factor because the corrugated wing generates shorter and several leading-edge vortex (LEV) structures than the flat plate and the ellipse during downstroke, thereby leading to elevated lift production of the corrugated wing. Shah et al [5,6] considered the effect of wing corrugation in three-dimensional numerical simulations using corrugated and smooth wings of Bombus pensylvanicus in hovering and forward velocities. The results proved that the morphologically-accurate model increased lift by 7-12% and decreased thrust by 49% at the higher forward speeds (2.5 and 4.5 m/s) as there were no major differences during hovering.…”