Wake-aerofoil interaction noise control with trailing-edge serrations

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

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Performance simulation of wind turbine with optimal designed trailing-edge serrations

Energy ◽

10.1016/j.energy.2021.122998 ◽

2021 ◽

pp. 122998

Author(s):

Teng Zhou ◽

Huijing Cao ◽

Mingming Zhang ◽

Caicai Liao

Keyword(s):

Wind Turbine ◽

Trailing Edge ◽

Performance Simulation ◽

Trailing Edge Serrations

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Aerodynamic Effects of Trailing Edge Serrations at Low Reynolds Numbers

10.2514/6.2022-1957 ◽

2022 ◽

Author(s):

Israel Bron Simplicio ◽

Giovanni F. Nino ◽

Robert Breidenthal

Keyword(s):

Reynolds Numbers ◽

Trailing Edge ◽

Low Reynolds Numbers ◽

Low Reynolds ◽

Trailing Edge Serrations

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Experimental study of wavy trailing edge serrations on flat rotor blades

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1970 ◽

2021 ◽

Vol 263 (5) ◽

pp. 1855-1866

Author(s):

Sai Manikanta Kaja ◽

K. Sriinivasan ◽

A. Jaswanth Kalyan Kumar

Keyword(s):

Experimental Study ◽

Noise Reduction ◽

Pitch Angle ◽

Acoustic Emissions ◽

Broadband Noise ◽

Rotor Blades ◽

Tonal Noise ◽

Trailing Edge ◽

Low Speeds ◽

Trailing Edge Serrations

A detailed experimental study is conducted to observe the effect of various parameters like wavelength, depth of serrations, and pitch angle on serrated blades' acoustic emissions at low speeds up to 2000 rpm. Experiments are conducted on flat blade rotors with sinusoidal serrations on the trailing edge of blades with different amplitudes and wavelengths. A total of 7 blades with different serration configurations, including a base configuration, are studied, five of them have serrations throughout the span of the blade, and one configuration has serration of varying amplitude on the farther half of the blade. It is observed that some blade configurations have resulted in tonal noise reduction noise as much as 8dB, whereas some of the serration configurations reduce very little to none, there is no significant effect of T.E serrations on the broadband noise emitted by the rotor. Directivity of noise generated from the rotor, the effect of serrations on the directivity of the noise is studied.

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