The shape of owl wings, which help the animals fly silently, can notify airfoil designs. Credit: Wang and Liu
Serrated edge of owl wings makes them quieter than other birds, can assist notify airfoil styles.
Trailing-edge sound is the dominant source of sound from aerial and turbine engines like those in aircrafts, drones, and wind turbines. Reducing this sound pollution is a significant environmental objective for some city locations.
In Physics of Fluids, by AIP Publishing, researchers from Xian Jiaotong University used the attributes of owl wings to inform airfoil style and considerably lower the trailing-edge noise.
” Nocturnal owls produce about 18 decibels less sound than other birds at comparable flight speeds due to their distinct wing setup,” stated author Xiaomin Liu. “Moreover, when the owl captures prey, the shape of the wings is also constantly changing, so the study of the wing edge setup during owl flight is of terrific significance.”
When air flow passes along the back of an airfoil, trailing-edge sound is generated. The circulation forms a rough layer of air along the upper and lower surfaces of the airfoil, and when that layer of air recedes through the trailing edge, it radiates and spreads sound.
Previous studies explored serrated tracking edges, discovering that the serrations efficiently minimize the sound of rotating equipment. The sound decrease was not universal, depending greatly on the last application.
” At present, the blade design of rotating turbomachinery has actually gradually developed, however the noise reduction technology is still at a bottleneck,” stated Liu. “The noise decrease capabilities of conventional sawtooth structures are limited, and some brand-new nonsmooth trailing-edge structures need to be proposed and developed to further tap the potential of bionic noise decrease.”
The group used noise computation and analysis software to perform a series of comprehensive theoretical studies of simplified airfoils with attributes similar to owl wings. They applied their findings to suppress the noise of turning machinery.
Improving the circulation conditions around the trailing edge and optimizing the shape of the edge reduced the noise. Surprisingly, uneven serrations minimized the sound more than their symmetric equivalents.
Sound decrease varied with different operating conditions, so the scientists stressed that the airfoil styles ought to be more evaluated based upon the specific application.
Wind turbines have complicated inbound circulation environments, which require a more basic sound decrease innovation. Taking a look at sound reduction strategies under the impact of different incoming circulations would make their conclusions more universal.
The researchers believe their work will act as an essential guide for airfoil style and sound control.
Reference: “Aeroacoustic investigation of uneven oblique trailing-edge serrations enlighted by owl wings” by Lei Wang and Xiaomin Liu, 18 January 2022, Physics of Fluids.DOI: 10.1063/ 5.0076272.