The Hydrodynamic Noise Suppression of a Scaled Submarine Model by Trailing-Edge Serrations

2019 ◽

Vol 283 ◽

pp. 08007

Author(s):

Hao Zhang ◽

Yongwei Liu ◽

Dejiang Shang

Keyword(s):

Noise Suppression ◽

Acoustic Analogy ◽

Back Wall ◽

Trailing Edge ◽

Airfoil Surface ◽

Eddy Simulation ◽

Fluctuation Pressure ◽

Flow Induced Noise ◽

Hydrodynamic Noise ◽

The Impact

When underwater vehicles are sailing, high hydrodynamic noise will be generated through the opening cavities due to the interaction of the surface and the fluids. In the paper, we had tested different forms of back wall chamfer by numerical calculation based on the method of large eddy simulation, to control the impact of the eddy and break the flow at the trailing edge of the cavity, which is with the dimension of 100mm wide, 120mm high and 100mm long. The angle and shape of the trailing edge chamfer are changed to control the flow of the cavity. We had also investigated the effect of hydrodynamic noise suppression through the simulation, which is based on the method of Lighthill’s acoustic analogy. The results show that the change of back wall chamfer can stabilize the movement of the eddies inside the cavity and reduce the fluctuation pressure at the trailing edge of the cavity. The suppression of flow-induced noise can be up to 5 dB, if the back-wall chamfer is with the airfoil surface and the angle of back wall chamfer is properly designed.

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Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020988229 ◽

2021 ◽

pp. 095441002098822

Author(s):

Dian Li ◽

Xiaomin Liu ◽

Lei Wang ◽

Fujia Hu ◽

Guang Xi

Keyword(s):

Flow Field ◽

Noise Reduction ◽

Numerical Study ◽

Barn Owl ◽

Aerodynamic Noise ◽

Frequency Noise ◽

Trailing Edge ◽

Reduction Mechanisms ◽

Trailing Edge Serrations ◽

Bionic Airfoil

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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