Thursday, November 14, 2013
The Amazing Flying Snakes Simulation
In this podcast, Lorena Barba and Anush Krishnan from George Washington University describe recent research into the amazing aerodynmics of flying snakes. "Flying snakes use a unique method of aerial locomotion: they jump from tree branches, flatten their bodies and undulate through the air to produce a glide. The shape of their body cross-section during the glide plays an important role in generating lift. This paper presents a computational investigation of the aerodynamics of the cross-sectional shape. We performed two-dimensional sim- ulations of incompressible flow past the anatomically correct cross-section of the species Chrysopelea paradisi, showing that a significant enhancement in lift appears at an angle of attack of 35◦, above Reynolds numbers 2000. Previous experiments on physical models also obtained an increased lift, at the same angle of attack. The flow is inherently three-dimensional in physical experiments, due to fluid instabilities, and it is thus intriguing that the enhanced lift appears also in the two-dimensional simulations. The simulations point to the lift enhancement arising from the early separation of the boundary layer on the dorsal surface of the snake profile, without stall. The separated shear layer rolls up and interacts with secondary vorticity in the near-wake, inducing the primary vortex to remain closer to the body and thus cause enhanced suction, resulting in higher lift." Read the Full Story.