Bats In Flight Reveal Unexpected Aerodynamics to researchers Kenneth Breuer and Sharon Swartz at Brown University:
Bat wings are highly articulated, with more than two dozen independent joints and a thin flexible membrane covering them. The videos, shot from four angles simultaneously and then synchronized, show how the complex movements of each wing stroke relate to overall flight speed, body position and angle of attack. Reflective markers placed on joints, along bones and at key points on the wing membrane allowed the researchers to accurately track the position and shape of bones throughout the wing stroke.Birds and insects can fold and rotate their wings during flight, but bats have many more options. Their flexible skin can catch the air and generate lift or reduce drag in many different ways. During straightforward flight, the wing is mostly extended for the down stroke, but the wing surface curves much more than a bird’s does — giving bats greater lift for less energy. During the up stroke, the bats fold the wings much closer to their bodies than other flying animals, potentially reducing the drag they experience. The wing’s extraordinary flexibility also allows the animals to make 180-degree turns in a distance of less than half a wingspan.