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Flying snakes a study in aerodynamic elegance

posted 2 Dec 2010, 09:39 by Mpelembe   [ updated 2 Dec 2010, 09:41 ]

Future developments in aeronautics may lie in the jungles of Southeast Asia, according to scientists researching the extraordinary gliding abilities of tree-dwelling snakes in the region. In a collaboration with National Geographic, the researchers have gone to great lengths to study the animals and how they manage to do what they do.

There are few creatures on earth that inspire as much cold fear and outight fascination as the snake but of the nearly 3000 identified species, there are five related 
species whose abilities have attracted special attention.

The Chrysopelea paradisi, commonly known as the "flying snake' is a tree-dweller, native to South and Southeast Asia. It flings itself off branches, surfing the air to the next tree or to the ground. Rather than flying like a bird or insect, the snake glides, often covering greater distances horizontally than vertically.

So fascinated is Jake Socha, an assistant professor in Engineering Science and Mechanics at Virginia Tech that, with a grant from the National Geographic Society he has travelled to Singapore to film the snakes in action and gather data about how they manage the feat.

"Being a cylinder, being a snake, it's probably the shape or the type of animal that you'd least expect to be able to fly through the air. And they actually can't fly like a bird or a bat or an insect. They can't go up, they can only go down, so really they're gliders," he said.

Socha has been studying the snakes for years, but the Singapore field experiment was the most ambitious study to date. Socha and his team launched flying snakes from the top of a 15-metre-tall tower and recorded the animals' trajectory using four cameras. This allowed the researchers to precisely track the variations in a snake's body positions as it went through its glide.

"What it does really is special behaviorally. So when it jumps into the air, it takes its body and it goes from being circular at a cross section, to something that is much more flattened," said Socha. "The other thing that it does behaviorally is that it undulates in the air. So when you see the animal gliding, it really looks like it's swimming through the air, and it might be in essence sort of surfing the waves that it's creating, the waves of air that it's pushing backwards."

An analysis of the video footage, coupled with computer models, show that the forces generated by the reptiles' undulating bodies partly counteract the gravitational forces pulling the snakes down. Socha says the animals are actually pushed upwards, because the upward component of the aerodynamic force is greater than their weight. The effect, though, is temporary, and the snakes eventually hit the ground.

"The snake is really the only animal that I've at least ever seen that has no appendages but can still cover significant horizontal distances while it's gliding, which is pretty awesome," says Dan Holden, a Virginia Tech graduate student who also worked on the aerodynamic models.

"And then when you typically think of the flying vehicles that we design, they always have wings to produce lift, so understanding what the snake is doing can have a significant impact on the field of aerodynamics and we could come up with clearly different designs than the ones we're used to making, and possibly increase the control and stability of these vehicles."

The Chrysopelea paradisi might very well hold the key to the next generation of flying vehicles. But for Jake Socha and his colleagues, they're endlessly fascinating in their own right.