The form of owl wings, which assist the animals fly quietly, can inform airfoil designs. Credit score: Wang and Liu
Serrated fringe of owl wings makes them quieter than different birds, may also help inform airfoil designs.
Trailing-edge noise is the dominant supply of sound from aeronautical and turbine engines like these in airplanes, drones, and wind generators. Suppressing this noise air pollution is a serious environmental aim for some city areas.
In Physics of Fluids, by AIP Publishing, researchers from Xi’an Jiaotong College used the traits of owl wings to tell airfoil design and considerably scale back the trailing-edge noise.
“Nocturnal owls produce about 18 decibels much less noise than different birds at related flight speeds on account of their distinctive wing configuration,” mentioned writer Xiaomin Liu. “Furthermore, when the owl catches prey, the form of the wings can also be continually altering, so the examine of the wing edge configuration throughout owl flight is of nice significance.”
Trailing-edge noise is generated when airflow passes alongside the again of an airfoil. The circulation varieties a turbulent layer of air alongside the higher and decrease surfaces of the airfoil, and when that layer of air flows again by the trailing edge, it scatters and radiates noise.
Earlier research explored serrated trailing edges, discovering that the serrations successfully scale back the noise of rotating equipment. Nonetheless, the noise discount was not common, relying closely on the ultimate software.
“At current, the blade design of rotating turbomachinery has steadily matured, however the noise discount expertise remains to be at a bottleneck,” mentioned Liu. “The noise discount capabilities of standard sawtooth buildings are restricted, and a few new nonsmooth trailing-edge buildings must be proposed and developed to additional faucet the potential of bionic noise discount.”
The workforce used noise calculation and evaluation software program to conduct a sequence of detailed theoretical research of simplified airfoils with traits harking back to owl wings. They utilized their findings to suppress the noise of rotating equipment.
Enhancing the circulation situations across the trailing edge and optimizing the form of the sting suppressed the noise. Apparently, uneven serrations diminished the noise greater than their symmetric counterparts.
Noise discount various with completely different working situations, so the scientists emphasised that the airfoil designs ought to be additional evaluated based mostly on the particular software.
For instance, wind generators have complicated incoming circulation environments, which require a extra common noise discount expertise. Inspecting noise discount methods below the affect of various incoming flows would make their conclusions extra common.
The researchers consider their work will function an vital information for airfoil design and noise management.
Reference: “Aeroacoustic investigation of uneven indirect trailing-edge serrations enlighted by owl wings” by Lei Wang and Xiaomin Liu, 18 January 2022, Physics of Fluids.
DOI: 10.1063/5.0076272
Post a Comment