An ornate, lime-green snake hangs from a branch. Upon spotting a predator, it suddenly propels itself into the air, flattening and wiggling its body until safely landing in a faraway tree.
Flying snakes sound like creatures from a bad B-movie, but these serpents are elegant gliders that have evolved a special skill that sets them apart. In two new studies, engineers have used simulations to try to decipher how the wingless reptile manages to remain airborne despite its lack of flight appendages.
While in the air, the snakes transform their cross-sectional shape, splaying their ribs and flattening their bodies. Through computational and physical modeling, researchers have discovered that this modified shape helps them become more aerodynamic and allows vortexes of air above their bodies to suction them upwards.
"Little by little, we built a theory about how the snakes are interacting with the air to generate very large lift forces," said aeronautical engineer Lorena Barba of George Washington University, who authored a study published in Physics of Fluids on Tuesday.
In a tornado, the low-pressure region is in the center, or eye. Similarly, researchers found areas of low pressure that form on top of the snake's body, creating a small amount of suction and helping to generate lift. In collaboration with flying-snake expert Jake Socha of Virginia Tech, Barba was able to visualize these swirls of air in a complex computer air-flow simulation.
An earlier study by Socha, published in the Journal of Experimental Biology in January, also investigated the flattened shape by using a 3-D printed snake model submerged in a tank of flowing water. Both experiments found that, surprisingly, the reptile has an excellent capacity to generate propelling flight forces, or lift.
They are called "flying snakes," but to be more precise, they are masters of the glide. Found in the lowland rainforests of Southeast and South Asia, flying snakes are fairly small creatures, growing to lengths of only a few feet and about the diameter of a lipstick. But upon jumping from a tall tree, say 30 feet, they can reach a horizontal distance of 10 times their body length.