January 30, 2014
The Aerodynamics Of Flying Snakes
[ Watch the Video: How Can A Snake Fly? ]
Brett Smith for redOrbit.com - Your Universe Online
The Paradise tree snake is probably best known for one unique behavior: its ability to "fly" from tree to tree.
New research from a team of American scientists has revealed that these snakes shape their body into an aerofoil mid-flight to allow them to glide around 100 feet from the top of a tree.
Study author Jake Socha, a biomechanics expert at Virginia Tech, said the snakes appear to be “slithering” in an S-shape as they move through the air and drop through the Southeast Asian rainforest canopy.
“They turn their whole body into one aerodynamic surface,” he said, adding, “they look like they are swimming.”
According to the study, which was published in The Journal of Experimental Biology, the snakes flex their ribs as they launch to extend and flatten themselves in an attempt to change their shape from a circular tube into an arched semi-circle.
“It looks like someone's version of a UFO,” said Socha, adding it's an unconventional shape for generating lift.
To analyze the aerodynamics of this shape, the study team used a 3-D printer to generate the very same UFO-like cross-section as the snake's body. Next, the team placed their model in a tank filled with water that flowed over the snake-shaped bar. While water is considerably denser than air, it can be used to model the airflow passing across a surface at an array of speeds.
Slanting the snake model at a variety of angles, which ranged from -10 to 60 degrees as the water passed over it at different speeds, the team measured the forces pulling on the model and discovered that at most angles the animal's unusual body shape generated sufficient lift to explain some of the snake's amazing gliding performance. However when the team tilted the model at 35 degrees, there was an immense spike in the lift produced by water flowing at higher speeds. More remarkably, when the model was positioned level with the flow, the fluid pushed it down. Also, when the team observed the water flowing around the model engineered with microscopic reflective beads, they could clearly see a vortex sitting beneath the level snake shape, sucking it down.
“Maybe the snake does hold part of its body flat at some point, using it as a mechanism for control,” Socha said, adding that twisting of the snake’s body in midair could allow it to fine tune the forces acting on their bodies – enabling precise flight control.
“If you make a rough estimate of the lift to drag ratio for the real animal, it appears to do better than what we got from this study,” he continued. “So even though this shape produced more lift than we were expecting, it doesn't get us the glide performance that snakes can attain, giving us a hint that there is something in what the animal is doing aerodynamically that is not captured by the cross-sectional shape alone”– a factor Socha and his team plan to investigate next.