The silent flight of owls could help suppress aircraft and turbine noise. A team from Chiba University in Japan has studied the unique features of owl wings that allow them to fly noiselessly.

The wings of these nocturnal creatures feature serrations on the leading edge, fringes on the trailing edge and velvet-like surfaces. Focusing on the serrations, Hao Liu and colleagues analysed owl-inspired feather wing models with and without the comb-like features to understand the role they play in noise suppression. “We wanted to understand how these features affect aerodynamic force production and noise reduction, and whether they could be applied elsewhere,” says Liu.

Wind-tunnel experiments

To study how air flows around an owl’s wing, the researchers used computational simulations, particle-image velocimetry (PIV) and wind-tunnel experiments. They found that the leading-edge serrations passively control the transition between streamline and turbulent air flows over the wings. At shallow wing angles, however, Liu and team also discovered there is a trade-off between force production and sound suppression, as the serrated edge reduces aerodynamic performance.

The team hope the work, published in Bioinspiration and Biomimetrics, may have industrial applications. "These owl-inspired leading-edge serrations, if applied to wind-turbine blades, aircraft wings or drone rotors, could provide a useful biomimetic design for flow control and noise reduction,” explains Liu, "At a time when issues of noise are one of the main barriers to the building of wind turbines, for example, a method for reducing the noise they generate is most welcome."