Bats use air bubbles to stay afloat in the air

Washington, February 29 : Swedish researchers have found out what enables bats to hover in the air like bumblebees, despite the fact that current aerodynamic theories suggest that they should not be able to do so.

Lund University biologist Anders Hedenstrom says that just like many insects, bats also use swirling "bubbles" of air called vortexes to stay afloat in mid-air.

The researcher revealed that the finding was based on a study wherein bats were put into smoky wind tunnel outfitted with special cameras and lasers.

"We imaged air flow around bats' wings to see how they shed these vortexes, which we think of as fingerprints. We found they give bats 40 per cent more efficiency in hovering flight," Live Science quoted him as saying.

Bats flap their wings nearly 15 times per second to hover in the air, generally to get at hard-to-reach food such as nectar-laced flowers. Because of their relatively large size compared to other hovering creatures, they need all of the help they can get.

While writing about their new findings in the journal Science, the researchers revealed that they saw a vortex generated at the front edge of the wing during each downward flap, while capturing the bats' in-flight behaviour in the wind tunnel.

"This leading edge vortex then swirls around the wing during the upward stroke. It stays attached to the wing, almost like it's glued there," he said.

The "sticky" vortex is like an air bubble that effectively changes the shape of the wing, forcing air to move around it in a more complex path, says Hedenstrom. The new airflow route gives the bat some extra lift by lowering the air pressure above the wing, he adds.

"Forward speed during flight generates lift, but hovering is all muscle power. You don't see animals much larger than this hovering, because they would need to beat their wings incredibly quickly," Hedenstrom said.

Now that it has been determined that vortexes are responsible for efficient hovering in bats, the researchers wish to study how bats control these vortexes.

The determination of this question may be helpful in designing a robotic bat model, says Hedenstrom.

ANI