If you’ve ever watched a bird land, you may have noticed how it rapidly pitches its wings upward at a high angle to execute a smooth landing. Other birds land by folding their wings as they perch instead, creating a sweeping motion as they decelerate.
Researchers in University of Central Florida’s (UCF) Department of Mechanical and Aerospace Engineering studied the aerodynamics of bird perching maneuvers for aircraft design. The team, led by aerospace engineering doctoral student Dibya Raj Adhikari, found the sweeping motion changes the shape of a bird’s wing, increases lift, and allows for better control of aerodynamic forces during a landing.
“A complete understanding of this perching maneuver would help to quantify the performance of the natural flyers and aid in the design of safer aircraft,” Adhikari says. “This perching maneuver also allows the birds to land smoothly within a short distance. So, a perching maneuver with swept-wing configuration can be an option where runway distance is an issue.”
The team used aluminum plates pushed through a tank of water containing silver-coated glass spheres to simulate the motion of bird wings. A rectangular plate was used to mimic a straight wing while a tapered plate was used to mimic a folded wing. The plates were moved at a constant speed for a few seconds, then tilted and shifted toward the tank wall during deceleration to imitate a bird pitching and heaving its wings during landing.
The researchers found the swept-wing motion stabilized the leading-edge vortex, one of the main mechanisms enhancing lift, leading to a better landing in birds and potentially in aircraft.