Aerodynamics of flying snakes

These animations show the vortex wake behind a snake cross-section (two-dimensional profile), obtained with full Navier-Stokes simulation. The solver is an immersed boundary method that uses GPU hardware, cuIBM (open-source under the MIT license). The cases shown vary in Reynolds number (Re=1000, 2000) and angle of attack (30, 35 and 40 degrees).

The cuIBM is fully validated with analytical solutions, published experimental data, and published numerical results. The validation report is available on the figshare repository.

This video supplements the paper "Lift and wakes in flying snakes" (Anush Krishnan, J. J. Socha, Pavlos Vlachos, L. A. Barba).

Krishnan, Anush; Barba, Lorena A. (2013): Flying snake wake visualizations with cuIBM. figshare.
 

Paper:

"Lift and wakes of flying snakes", Anush Krishnan, John J. Socha, Pavlos V. Vlachos, L. A. Barba. Phys. Fluids, 26:031901 (2014). DOI 10.1063/1.4866444. Preprint arXiv:1309.2969
 

Abstract:

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 simulations 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 degrees, 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.

For more details please visit  http://lorenabarba.com/news/submitted-lift-and-wakes-of-flying-snakes