Invention of New Robots is by Helped by Flying Snakes

Science News -- December 14, 2022: In order to avoid predators or to move fast and effectively, flying snakes move
from the tops of trees to the ground

by undulating side to side. Researchers study this lift generating process. The researchers created a computational model using information from high-speed video recordings of the snakes, and
they took into account a number of characteristics to determine which were crucial for producing glide, such as the angle
of attack the snake forms with the approaching airflow and the frequency of its undulations.

Robots may now move in ways that resemble those of animals, such as walking and swimming. Scientists are currently thinking of ways to create robots that resemble the gliding motion used by flying snakes.

Researchers from Virginia Tech and the University of Virginia investigated the lift-producing mechanism of flying snakes in Physics of Fluids, published by AIP Publishing. Flying snakes undulate as they descend from the tops of trees to the ground
to evade predators or to move quickly and effectively. Snakes can glide for a long distance—up to 25 meters from a 15-meter tower—due to the undulation.

The researchers used data from high-speed footage of flying snakes to construct a computational model to explain how the undulations provide lift. The snake's body's cross-sectional shape, which resembles an extended frisbee or flying disc, is a crucial aspect of this concept.

To comprehend how the snake can glide thus far, one must first understand its cross-sectional shape.
When a frisbee is spun, it increases the air pressure underneath it and creates suction on top, which lifts the disc into the air. The snake undulates from side to side, producing low pressure above its back and high pressure beneath its belly, to assist produce the same type of pressure difference over its body. The snake is raised as a result, enabling it to float through the air.

"The snake's horizontal undulation creates a series of major vortex structures, including leading edge vortices, LEV, and trailing edge vortices, TEV," said author Haibo Dong of the University of Virginia. "The formation and development of the LEV on the dorsal, or back, surface of the snake body plays an important role in producing lift."
Near the head, the LEVs begin and move back along the body. The researchers discovered that the LEVs remain in place for longer periods of time before being shed at the snake's body curves. These curves, which are crucial to comprehending the lift mechanism, are created during the undulation.

In order to identify which characteristics were crucial for producing glide, the group took into account a number of characteristics, including the angle of attack the snake forms with the incoming airflow and the frequency of its undulations. Flying snakes often undulate approximately 1-2 times per second in their native habitat. Unexpectedly, the researchers discovered that faster undulation lowers aerodynamic performance.

"The general trend we see is that a frequency increase leads to an instability in the vortex structure, causing some vortex tubes to spin. The spinning vortex tubes tend to detach from the surface, leading to a decrease in lift," said Dong.

The researchers anticipate that their findings will contribute to a better understanding of gliding motion and to the development of gliding snake robots that are better designed.

Information Source:
Group of US Physicists. Computational modeling explains the method by which an undulating, flying snake may achieve lift and glide hundreds of feet, providing scientists with important information as they work to develop new types of robots. ScienceDaily. Website: www.sciencedaily.com/releases/2022/12/221213121455.htm>, ScienceDaily, 13 December 2022.

WNCTIMES by Marjorie Farrington