Aerodynamics of Insect Flight In TurbulentFlow

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The aerodynamics of insect flight currently receives high attention. The fundamentals of insect flight were first explored assuming that insects move in quiescent air. However, natural environment is typically turbulent, but we know very little on how insects manage to fly on windy days. For man-made micro air vehicles it is likewise important to fly under difficult flow conditions. This project proposes to investigate the interaction of insects with turbulence from complementary perspectives of experimental biology and computational fluid dynamics. We will define a set of model turbulent flows with reproducible statistical properties, varying systematically the energy content of the scales of turbulent motion, with similar flow conditions in experiments and numerical simulations. We also put a major emphasis on the significance of wing elasticity, and devise a suitable flexible wing model that closely mimics the elastic properties of real wings, which we measure in an experimental facility. Biological experiments account for the whole complexity of animals, including the brain, sensory system and the resulting changes in the wing-beat kinematics under perturbed flight conditions. Numerical simulations allow studying isolated effects and thus to reduce the problem's complexity. We combine biological experiments on tethered and freely flying insects on the one hand, and numerical simulations of model insects with rigid and flexible wings in tethered and free flight in a similar turbulent flow environment on the other hand. This allows giving at least partial answers to the three major questions we consider: (i) What are impacts, benefits and limitations of environmental turbulence on the aerodynamics of flapping insect flight? (ii) How does turbulence affect the energetic cost of flapping flight with flexible and rigid wings? (iii) What behavioral strategies do insects employ to cope with turbulent perturbations? These questions are relevant for both fundamental and applied research, and their interdisciplinary nature requires employing several perspectives.