Scientists Explain Owls' Mysterious, Silent Flight

Ever wonder how owls seem to swoop in so effortless, with a nearly silent flight?

Well, thanks to findings by researchers from the American Physical Society's Division of Fluid Dynamics, bringing the silent flight of the owl into the designs of aircraft, wind turbines and submarines is one step closer.

"Owls possess no fewer than three distinct physical attributes that are thought to contribute to their silent flight capability: a comb of stiff feathers along the leading edge of the wing; a flexible fringe a the trailing edge of the wing; and a soft, downy material distributed on the top of the wing," explained Justin Jaworski, assistant professor in Lehigh University's Department of Mechanical Engineering and Mechanics.

His group is exploring whether owl stealth is based upon a single attribute or the interaction of a combination of attributes. "We also predicted that the dominant edge-noise source could be effectively eliminated with properly tuned porous or elastic edge properties, which implies that that the noise signature from the wing can then be dictated by otherwise minor noise mechanisms such as the 'roughness' of the wing surface," he added, via a press release.

Background information from the study notes that an owl's wings are composed of a rather rough surface that help provide a silent flight. Researchers believe this could help eliminate sound at the source through a novel mechanism that's much different from normal sound absorbers.

"Our current work predicts the sound resulting from air passing over the downy material, which is idealized as a collection of individual flexible fibers, and how the aerodynamic noise level varies with fiber composition," Jaworski said. "If the noise-reduction mechanism of the owl down can be established, there may be far-reaching implications to the design of novel sound-absorbing liners, the use of flexible roughness to affect trailing-edge noise and vibrations for aircraft and wind turbines, and the mitigation of underwater noise from naval vessels."

More information regarding the study will be presented at the 66^th Annual Division of Fluid Dynamics Meeting.