Flying snakes help scientists design new robots

(1) A paradise tree snake, Chrysopelea paradise, floating in the air. (2) 3D snake body model with skeleton articulation for horizontal undulation. (3) The swirl structures of the waving serpent. (4) Swirl contours with openings at different slice segments along the body. (5) Effects of undulating frequency on the aerodynamic performance of the gliding snake. Credits: Jack Socha (1) and Yuchen Gong (2-5)

Robots are designed to mimic animal movements such as walking and swimming. Scientists are now considering how to design robots that mimic the gliding motion exhibited by flying snakes.

Inside Fluid PhysicsResearchers from the University of Virginia and Virginia Tech have discovered the elevator production mechanism of flying snakes that swing from side to side as they move from the top of trees to the ground to evade predators or move quickly and efficiently. The ripple allows the snakes to glide over long distances of up to 25 meters from a 15-metre tower.

To understand how ripples provide lift, the researchers developed a computational model derived from data from high-speed videos of flying snakes. An important component of this pattern is the cross-sectional shape of the snake’s body, resembling an elongated frisbee or a flying disc.

The cross-sectional shape is essential to understanding how the snake was able to glide so far. In a frisbee, the spinning disk creates high air pressure under the disk and suction at the top, raising the disk into the air. The snake sways from side to side to help create the same kind of pressure difference throughout its body, creating a low pressure zone on its back and a high pressure zone under its belly. This lifts the snake and allows it to glide through the air.

“The horizontal undulation of the snake creates a number of major eddy structures, including the leading edge vortices, the LEV, and trailing edge vortices, the TEV,” said co-author Haibo Dong of the University of Virginia. “The formation and development of LEV on the dorsal or dorsal surface of the snake body plays an important role in lift generation.”

LEVs form near the head and travel backwards throughout the body. Investigators have found that LEVs are held longer in the folds of the snake’s body before molting. These curves are formed during surge and are key to understanding the lift mechanism.

The group evaluated various characteristics of the snake, such as the angle of attack created by the oncoming airflow and the frequency of its ripples, to determine which were important in gliding. In their natural habitat, flying snakes typically fluctuate at a frequency of 1-2 times per second. Surprisingly, the researchers found that faster surge reduces aerodynamic performance.

“The general trend we see is that an increase in frequency causes an instability in the vortex structure, causing some of the vortex tubes to rotate. The rotating vortex tubes tend to separate from the surface, which leads to a reduction in buoyancy,” Dong said.

The scientists hope their findings will lead to a better understanding of gliding motion and a more suitable design for gliding snake robots.

The paper “Computational analysis of eddy dynamics and aerodynamic performance in flying snake-like glide flight with horizontal undulation” was written by Yuchen Gong, Junshi Wang, Wei Zhang, Jake Socha, and Haibo Dong. The article will appear in: Fluid Physics on 13 December 2022.

More information:
Yuchen Gong et al., Computational analysis of eddy dynamics and aerodynamic performance in gliding snake-like gliding flight with horizontal undulation, Fluid Physics (2022). DOI: 10.1063/5.0125546

Provided by the American Institute of Physics

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