Meeting Abstract

69.1  Jan. 7  Understanding aerodynamic force generation in gliding snakes using physical models MIKLASZ, K.A.*; SOCHA, J.J.; LABARBERA, M.; University of Chicago; Argonne National Laboratory; University of Chicago kmiklasz@gmail.com

Snakes of the genus Chrysopelea, the only limbless animal flyers, have no specialized structures used to produce lift, suggesting that snakes use their body as a functional �wing�. When airborne, snakes dorsoventrally flatten the body by expanding the ribcage, creating a concave shape whose aerodynamic characteristics are currently unknown. In this study, we determine the aerodynamic characteristics of this cross-sectional shape by measuring the lift and drag coefficients of model body segments in a wind tunnel. The concavity, edge sharpness, and backbone protrusion of the models were varied in order to determine the effect of specific aspects of cross-sectional shape on force generation. The models exhibited maximum lift-to-drag ratios of 2.6-2.9 (corresponding to minimum glide angles of 19�-20�) and lift and drag coefficients of 1.4 and 0.5 at the angle of attack where minimum glide angle occurs. These values fall within the range of previous estimates based on actual snake trajectories. Two features of the models illustrate that snakes can use multiple angles of attack and still perform near maximally. First, the lift-to-drag ratio decreases gradually after stall, which occurs near 30�. Second, there is a 20� range of angles of attack where lift-to-drag is relatively high. When two model segments were placed in series to more closely mimic the snake�s body posture in flight , the lift-to-drag ratio of the posterior segment significantly increased. Overall, the lift and drag coefficients found in this study indicate that treating the snake�s body segments as separate airfoils may account for most of the forces that snakes generate while gliding, suggesting that conventional static-wing aerodynamics can explain how snakes glide.