Abstract
Despite their lack of appendages, flying snakes (genus Chrysopelea) exhibit aerodynamic performance that compares favorably to other animal gliders. We wished to determine which aspects of Chrysopelea’s unique shape contributed to its aerodynamic performance by testing physical models of Chrysopelea in a wind tunnel. We varied the relative body volume, edge sharpness, and backbone protrusion of the models. Chrysopelea’s gliding performance was surprisingly robust to most shape changes; the presence of a trailing-edge lip was the most significant factor in producing high lift forces. Lift to drag ratios of 2.7–2.9 were seen at angles of attack (α) from 10–30°. Stall did not occur until α > 30° and was gradual, with lift falling off slowly as drag increased. Chrysopelea actively undulates in an S-shape when gliding, such that posterior portions of the snake’s body lie in the wake of the more anterior portions. When two Chrysopelea body segment models were tested in tandem to produce a two dimensional approximation to this situation, the downstream model exhibited an increased lift-to-drag ratio (as much as 50% increase over a solitary model) at all horizontal gaps tested (3–7 chords) when located slightly below the upstream model and at all vertical staggers tested (±2 chords) at a gap of 7 chords.
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Acknowledgements
We thank Mark Stremler, Saad Ragab, and Mark Cramer for helpful discussions on the aerodynamic data in this study, and Pavlos Vlachos for a critical reading of the manuscript and advice. The comments of two anonymous reviewers greatly improved the manuscript. This project was part of an undergraduate honors research thesis (KM) at the University of Chicago; thanks to Heinrich Jaeger and Henry Frisch for their support and advice.
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Michael LaBarbera and John J. Socha contributed equally to this work.
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Miklasz, K., LaBarbera, M., Chen, X. et al. Effects of Body Cross-sectional Shape on Flying Snake Aerodynamics. Exp Mech 50, 1335–1348 (2010). https://doi.org/10.1007/s11340-010-9351-5
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DOI: https://doi.org/10.1007/s11340-010-9351-5