Wing-body interaction mechanisms augment forward flight of hawk moths

Recent work has investigated the flapping-wing aerodynamics of flying insects, with the ultimate goal of exploiting the mechanical findings to build bio-inspired flying robots. However, most computational fluid dynamics (CFD) and experimental studies have focused on hovering flights associated with single or paired wing models.

Xue et. al. aimed to understand how flying insects regulate their wing kinematics and body motion as a function of flight velocity. They created a high-fidelity CFD wing-body model based on the realistic morphology and wing-body kinematics of the hawk moth, Manduca Sexta.

“The aerodynamics and energetics, particularly in terms of the aerodynamic interaction between the flapping wings and the flying body, remain open questions,” said author Hao Liu. “Motivated by this, here we address a comprehensive numerical study of hawk moth aerodynamics and energetics at various flight velocities, including hovering and forward flights.”

The researchers carried out a series of numerical simulations of hawk moth flights at various flight velocities by employing an in-house bio-inspired dynamic flight simulator, based on their previous work.

The results confirmed that mechanisms based on both leading-edge vortices and body vortices — as well as their velocity-dependent interactions — contribute to the aerodynamic force for forward flight of the hawk moth. Also, the body vortex created by wing-body interactions augments the vertical force, particularly for forward flight of intermediate and high velocities. Lastly, high-aspect ratio wings enhance both wing- and body-based vertical force for forward flight at various velocities.

The systematic analysis provides an overall understanding of the wing-body interaction in terms of the unsteady aerodynamics and energetics for various forward flight velocities of the hawk moth, which should help guide the design of biomimetic flapping micro-aerial vehicles.

Source: “Effects of wing-body interaction on Hawk moth aerodynamics and energetics at various flight velocities,” by Yujing Xue, Xuefei Cai, and Hao Liu, Physics of Fluids (2022). The article can be accessed at http://doi.org/10.1063/5.0087161 .