Aerodynamics of insect flight and modelling of wing flexibility

Hung Truong
I2M, Aix-Marseille Université

Date(s) : 24/03/2021   iCal
14 h 00 min - 15 h 00 min

Insects have fascinated a large, interdisciplinary community of engineers, biologists, physicists and mathematicians for a long time with their extraordinary capabilities of flying by flapping their wings. Insect flight has been extensively studied in the past assuming that insects fly with rigid wings in quiescent flow conditions. In the real world, however, most insect wings are complex structures that consist of a thin, flexible membrane supported by a network of veins. The aim of this project is to investigate the influence of wing flexibility on the aerodynamic performance of insects. For this purpose, a wing model has been developed using a mass-spring system where the wing is discretized by mass points connected by springs. Based on different mechanical behaviors, veins are modeled as a rod using extension and bending springs while membranes are modeled as a thin sheet using extension springs only. This functional approach allows us to mimic the distinctive structure and dynamics of insect wings. The wing model is then coupled with a fluid solver which is based on a spectral discretization of the three-dimensional penalized Navier–Stokes equations. The code is designed to run on massively parallel supercomputers for high-resolution computations. After being validated with respect to previous works, the code is firstly employed to simulate a tethered bumblebee with flexible wings. In order to analyze the effect of wing flexibility, the Young’s modulus of wing cuticle is varied to make a comparison between two different wing models that we refer to as flexible and highly flexible. We then examine a second species which is Calliphora vomitoria (blowfly) in a tethered flight context. Using covariance matrix adaptation evolution strategy, the wing stiffness is optimized by comparing the wing model with a set of experimental data of wing deformation in response to static point forces. Our studies show that wing flexibility plays an important role in minimizing flight energetic cost. Moreover, the wing inertia also helped to damp out the fluctuation of the aerodynamic force and thus stabilized the insect during flight.

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