Helical vortices generated by flapping wings of bumblebees

ORAL

Abstract

We analyze high resolution numerical simulation data of a bumblebee with fixed body and prescribed wing motion, flying in a numerical wind tunnel, presented in [Engels et al., Phys. Rev. Lett., 116, 028103, 2016]. The inflow condition of the tunnel varies from unperturbed laminar to strongly turbulent. The flow generated by the flapping wings indicates the important role of the leading edge vortex (LEV), responsible for elevated lift production and which is not significantly altered by the inflow turbulence. The LEV has a conical structure due to the three-dimensional motion of the wings. This flow configuration produces strong vorticity on the sharp leading edge and the outwards velocity (from the root to the tip of the wing) in the spanwise direction. Flow visualizations show that the generated vortical structures are characterized by a strong helicity. We study the evolution of the mean helicity for each wing and analyze the impact of turbulent inflow.

*We thankfully acknowledge financial support from the French-German AIFIT project funded by DFG and ANR (Grant 15-CE40-0019). DK gratefully acknowledges financial support from the JSPS postdoctoral fellowship.

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Authors

  • Marie Farge

    • LMD-IPSL-CNRS, Ecole Normale Sup\'erieure, Paris, France
    • LMD-CNRS, Ecole Normale Sup\'erieure, Paris, France

  • Thomas Engels

    • ISTA, Technische Universit\"at Berlin, Berlin, Germany

  • Dmitry Kolomenskiy

    • Biomechanical Engineering Laboratory, Chiba University, Chiba, Japan

  • Kai Schneider

    • I2M-CNRS, Centre de Math\'ematiques et d'Informatique, Aix-Marseille Universit\'e, Marseille, France

  • Fritz Lehmann

    • Department of Animal Physiology, Universi\at Rostock, Rostock, Germany

  • J\"orn Sesterhenn

    • ISTA, Technische Universit\"at Berlin, Berlin, Germany