Helical vortices generated by flapping wings of bumblebees

TL;DR

This study uses high-resolution simulations to analyze the aerodynamics of bumblebee wings, focusing on vortex formation, helicity, and the effects of turbulence on lift generation.

Contribution

It provides new insights into how leading edge vortices and helicity are generated and maintained in flapping wings under various flow conditions.

Findings

Leading edge vortices are robust against inflow turbulence.

Helicity analysis reveals multi-scale vortex contributions.

Rigid wing flapping enhances lift through vortex dynamics.

Abstract

High resolution direct numerical simulations of rotating and flapping bumblebee wings are presented and their aerodynamics is studied focusing on the role of leading edge vortices and the associated helicity production. We first study the flow generated by only one rotating bumblebee wing in circular motion with $45^{\circ}$ angle of attack. We then consider a model bumblebee flying in a numerical wind tunnel, which is tethered and has rigid wings flapping with a prescribed generic motion. The inflow condition of the wind varies from laminar to strongly turbulent regimes. Massively parallel simulations show that inflow turbulence does not significantly alter the wings' leading edge vortex (LEV), which enhances lift production. Finally, we focus on studying the helicity of the generated vortices and analyze their contribution at different scales using orthogonal wavelets.