Flow characteristics of aerial swimmers: flapping wing propulsion of tiny insects flying at extremely low Reynolds numbers
Sensory and Behavioural Biology
Experimental Condensed Matter Physics
Mathematics
Final Report Abstract
Main goal of this project was to evaluate the aerodynamic principles of insect flight with bristled, oscillating wings. Insect wings are hybrid structures that are typically composed of veins and solid membranes. In some of the smallest flying insects, however, the wing membrane is replaced by hairlike bristles attached to a solid root. Bristles and membranous wing surfaces coexist in small but not in large insect species. There is no satisfying explanation for this finding as aerodynamic force production is always smaller in bristled than solid wings. To gain insights into aerodynamic mechanisms, we developed insect handling tools and studied wing motion in miniature insects during tethered and free flight. Extended kinematic and morphological measurements of miniature insects allowed estimations of air flows, aerodynamic force production and aerodynamic efficiency using computational fluid dynamics and robotic experiments. The experiments were performed at Reynolds numbers typical for flight of insects below one millimeter body length. Our findings highlight wing flapping aerodynamics at highly viscous flows that result in low lift coefficients, elevated drag coefficients, and aerodynamic Froude-efficiencies for flight below 10%. Data suggest that miniature insects may fly with bristled and solid wing surfaces at similar efficacy, while larger insects must use membranous wings for an efficient production of flight forces. In miniature beetles, the oscillating elytra serve as an inertial brake that stabilizes body motion of the insect. The above findings are significant for an in-depth understanding of locomotor propulsion in the smallest flying insects and may help to construct biomimetic air vehicles using flapping wings for propulsion.
Publications
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(2019). Local deformation and stiffness distribution in fly wings. Biol. Open 8, bio038299
Wehmann, H.-N., Heepe, L., Gorb, S. N., Engels, T. and Lehmann, F.-O.
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(2020) Wing design in flies: properties and aerodynamic function. Insects 11, 466
Krishna, S., Cho, M., Wehmann, H.-N., Engels, T. & Lehmann, F.-O.
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(2020). Aerodynamic performance of a bristled wing of a very small insect. Exp. Fluids 61, 1-13
Kolomenskiy, D., Farisenkov, S., Engels, T., Lapina, N., Petrov, P., Lehmann, F.-O., Onishi, R., Liu, H. and Polilov, A. A.
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(2020). Three-dimensional wing structure attenuates aerodynamic efficiency in flapping fly wings. J. R. Soc. Interface 17, 20190804
Engels, T., Wehmann, H.-N. and Lehmann, F.-O.
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(2021) An experimental data-driven mass-spring model of flexible Calliphora wings. Bioinsp. Biomim. 17, 026003
Truong, H., Engels, T., Wehmann, H., Kolomenskiy, D., Lehmann, F.-O. & Schneider, K.
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(2021). Flight efficiency is a key to diverse wing morphologies in small insects. J. R. Soc. Interface 18, 20210518
Engels, T., Kolomenskiy, D. and Lehmann, F.-O.
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(2021). Vortex trapping recaptures energy in flying fruit flies. Sci. Reports 11, 1-7
Lehmann, F.-O., Wang, H. and Engels, T.
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(2022). Efficiency and aerodynamic performance of bristled insect wings depending on Reynolds number in flapping flight. In: Advances in Biological Flows and Biomimetics, Volume II. Fluids, 7, 75
O'Callaghan, F., Sari, A., Ribak, G. and Lehmann, F.-O.
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(2022). Flight activity and age cause wing damage in house flies. J. Exp. Biol. 225, jeb242872
Wehmann, H.-N., Engels, T. and Lehmann, F.-O.
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(2022). Novel flight style and light wings boost flight performance of tiny beetles. Nature, 602, 96–100
Farisenkov, S. E., Kolomenskiy, D., Petrov, P. N., Engels, T., Lapina, N. A., Lehmann, F.-O., Onishi, R., Liu, H. and Polilov, A. A.
