Researchers uncover secrets behind the silent flight of owls

Investigating silent flying mechanisms through numerical simulations


Owls possess the remarkable ability to navigate the skies without producing any noticeable noise. This unique characteristic allows them to hunt with precision while remaining undetected. Scientists have previously identified a correlation between micro-fringes on owl wings and their silent flight, but the exact mechanisms behind this phenomenon have remained elusive.

To unravel the secrets of silent owl wings, Professor Hao Liu and his team from Chiba University in Japan embarked on a groundbreaking study. Their research aimed to understand how these micro-fringes influence both the sound and aerodynamic performance of owl wings.

The team employed computational fluid dynamic simulations to construct three-dimensional models of real owl wings. These models, with and without micro-fringes, were used to investigate the impact of these structures on owl flight. By combining large eddy simulations and the Ffowcs-Williams-Hawkings analogy, the researchers were able to analyze the fluid flow and noise levels of the owl wings.

The study conducted by Professor Hao Liu and his team at Chiba University has taken us one step closer to unraveling the mysteries of silent owl flight. By investigating the effects of micro-fringes on owl wings, they have provided valuable insights into the aeroacoustic mechanisms that enable owls to fly silently.  

The simulations revealed that the micro-fringes significantly reduced noise levels, particularly at high angles of attack, while maintaining comparable aerodynamic performance. The team identified two key mechanisms through which the micro-fringes influence airflow. Firstly, the fringes disrupt trailing edge vortices, reducing fluctuations in airflow. Secondly, they minimise flow interactions between feathers at the wingtips, thereby suppressing the shedding of wingtip vortices. These combined effects enhance both aerodynamic force production and noise reduction.

Professor Liu emphasises the significance of these findings, stating that "Understanding the precise role of micro-fringes in owl wings will enable us to apply them in developing practical low-noise fluid machinery." The implications of this research extend beyond the realm of ornithology. The study's insights could be applied to various fields, including drones, wind turbines, propellers, and even flying cars, where noise reduction is crucial.

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