Japanese and Chinese researchers have teamed up to study the unique features of owl wings in an attempt to inspire ideas for making quieter aircraft and wind turbines. The study findings were published in the journal Bioinspiration and Biometrics.
Owls have the ability of silent flight, which is characteristic of their wing design, namely leading-edge serrations, velvet-like surfaces, and trailing-edge fringes, Professor Hai Liu with Chiba University and the lead author of the study said. These characteristics piqued the interest of researchers who wanted to understand how the bird’s unique wing features affect noise reduction and production of aerodynamic force, and if they could use like-kind features to help make aircrafts and wind turbines quieter.
During the study, researchers examined and analyzed feather wing models inspired by owls, both with the leading-edge serrations and without them. In a low-speed wind tunnel, they utilized a mathematic model for turbulence to simulate airflow, Particle-Image Velocimetry (PIV), and force measurements.
Researchers found that the leading-edge serrations found in owl wings play an important role in the production of sound and aerodynamic force. For example, the serrations can passively control turbulent airflow that goes over the upper wing surface at angles of attack measuring 0 and 20 degrees, as well as the transition between laminar or streamline airflow.
However, they found a tradeoff between sound suppression and force production, Professor Liu said. Compared to clean leading edges, leading-edge serrations reduce aerodynamic performance at angles of attack lower than 15 degrees, but they can achieve aerodynamic performance and noise reduction at angles of attack greater than 15 degrees, which is what owls are often capable of in flight.
Noise is one of the main issues in building wind turbines. However, researchers believe that by applying leading-edge serrations found in owl wings to aircraft wings, wind turbine blades, and drone rotors, it is possible to provide a biometric design that will control airflow and reduce noise.
By Trixie Dillwood