A group of researchers at the Iowa State University in the US are exploring the behaviours of owl wings in order to develop bio-inspired ideas for quieter aircraft.

The team is using a specimen of a short-eared owl’s wing to carry out the research, which could also be used to develop ultra-quiet wind turbines.

3D-printing technology has also been used to create various models of aircraft propeller blades inspired by owl wings.

Iowa State University aerospace engineering assistant professor and research team member Anupam Sharma said: “The owl is almost completely silent in-flight.

“Owls are not only silent in gliding flight, but also in flapping flight, which is amazing.”

The researcher also noted that the three-part ‘owl hush kit’ featured in the wing is enabling the bird to fly silently.

In order to know the hush kit’s ability to manipulate air flow, turbulence and pressure to produce silent flight, the researchers have been scanning owl wing specimens, creating digital models and running several simulations.

The simulations use more than 16,000 processors provided by the supercomputing facilities at Argonne National Laboratory in Illinois, US.

“Owls are not only silent in gliding flight, but also in flapping flight, which is amazing.”

In addition, Sharma’s collaborators at Virginia Tech have designed model airfoils, the curved shape of an aircraft wing, with a regular series of small, thin ‘finlets’ and canopies near the trailing edge of the blade and running parallel to the airflow.

Also inspired by owl wings, the airfoil designs were experimented by the team at Virginia Tech.

Following the experiments, both research teams compared the performance of the owl-inspired airfoils to a standard, flat-surfaced airfoil.

According to Sharma, the computer simulations showed the owl-inspired airfoils substantially reduced the unsteady pressure on the back end of the blade surface, and the sound radiated by the owl-inspired design was reduced by up to 5db over a wide frequency range.

The noise reduction was observed without making any compromise with the aerodynamic performance.

The research at the Iowa State University is supported by a five-year $500,000 CAREER grant from the National Science Foundation.

Iowa Space Grant Consortium, National Science Foundation and Argonne Leadership Computing Facility are also supporting the research.

Image: 3D-printed models of aircraft propeller blades with serrated leading edges inspired by owl wings. Photo: courtesy of Iowa State University of Science and Technology.