scholarly journals A study of noise reduction mechanisms of jets with fluid inserts

2020 ◽  
Vol 476 ◽  
pp. 115331 ◽  
Author(s):  
Chitrarth Prasad ◽  
Philip J. Morris
Keyword(s):  
Noise Reduction ◽  
Reduction Mechanisms

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

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.

Noise reduction mechanisms in supersonic jets with porous centerbodies

AIAA Journal ◽  
1985 ◽  
Vol 23 (5) ◽  
pp. 678-684 ◽  
Author(s):  
V. Kibens ◽  
R. W. Wlezien
Keyword(s):  
Noise Reduction ◽  
Supersonic Jets ◽  
Reduction Mechanisms

Skewed blades in low pressure fans - A survey of noise reduction mechanisms

1997 ◽  
Author(s):  
Th. Carolus ◽  
M. Beiler ◽  
Th. Carolus ◽  
M. Beiler
Keyword(s):  
Noise Reduction ◽  
Low Pressure ◽  
Reduction Mechanisms

Noise reduction mechanisms for the inclined leading edge vaned diffuser in a centrifugal fan

2017 ◽  
Vol 231 (1) ◽  
pp. 68-83 ◽  
Author(s):  
Gong Wu Qi ◽  
Zhang Wei
Keyword(s):  
Noise Reduction ◽  
Pressure Fluctuation ◽  
Numerical Study ◽  
Second Harmonic ◽  
Leading Edge ◽  
Centrifugal Fan ◽  
Fan Noise ◽  
Vaned Diffuser ◽  
Reduction Mechanisms ◽  
Centrifugal Fans

An experimental and numerical study to explore the noise reduction mechanism for the inclined leading edge vaned diffuser in centrifugal fans is described. Inclined leading edge vaned diffuser is useful in improving fan performance, increasing operating range, and reducing fan noise. The generation of fan noise is related to the pressure fluctuation on the diffuser vane surface, particularly the leading edge. Numerical results show that pressure fluctuation on the inclined leading edge vaned diffuser surface remarkably decreases, unlike that of the original diffuser. The pressure fluctuation is dominated by the components at the blade passing frequency and its second harmonic.

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