The Noise-Reduction Characteristics of Microstructure of Dragonfly Wing Leading Vein

Shan Jiang; Yong Hu; Qiang Li; Hongde Wang; Yang Lin; Xiaoqin Zhou; Qiang Liu

doi:10.3390/app11072970

The Noise-Reduction Characteristics of Microstructure of Dragonfly Wing Leading Vein

Applied Sciences ◽

10.3390/app11072970 ◽

2021 ◽

Vol 11 (7) ◽

pp. 2970

Author(s):

Shan Jiang ◽

Yong Hu ◽

Qiang Li ◽

Hongde Wang ◽

Yang Lin ◽

...

Keyword(s):

Noise Reduction ◽

Leading Edge ◽

Low Noise ◽

Triangular Prism ◽

Test Results ◽

Test Platform ◽

Computational Fluid Dynamics Cfd ◽

Reduction Characteristics ◽

Serrated Structure ◽

Dragonfly Wings

Dragonfly wings have many excellent functions, such as superhydrophobic, fatigue resistance, anti-reflection, etc. However, there are few reports on the low noise flight of dragonfly wings. For this reason, the microgeometry of dragonfly wings was studied in this paper to reveal the mechanism of low-noise flight of dragonfly leading veins. The micromorphology of dragonfly wings was observed by scanning electron microscopy. It was found that the leading-edge veins of dragonfly wings have a triangular prism-like serrated structure, which has been proven to have the effect of improving aeroacoustics. According to the principle of scale law of flying organisms, a bionic model with the leading-edge microstructure of dragonfly’s front wing was established, and computational fluid dynamics (CFD) analysis of serration bionic microstructure was carried out. The effects of geometric parameters, such as height, width and overall amplification factor of microstructure on aeroacoustics were obtained. The distribution of pressure fluctuation on the surface of the bionic wing was also analyzed in this paper. It was found that the serrated microstructure can significantly suppress the noise generation in the mid-frequency band. Finally, wind tunnel tests were simulated using a designed low-noise rotating test platform. The test results confirmed that the serration microstructure has certain noise-reduction characteristics.

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On the reductions of aerofoil-turbulence interaction noise through multi-wavelength leading edge serrations

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

10.1177/0954410020965747 ◽

2020 ◽

pp. 095441002096574

Author(s):

S Narayanan ◽

Sushil Kumar Singh

Keyword(s):

Noise Reduction ◽

Maximum Amplitude ◽

Leading Edge ◽

Emission Angle ◽

Broadband Noise ◽

Dual Wavelength ◽

Flat Plates ◽

Wide Range ◽

Multi Wavelength ◽

Reduction Characteristics

This paper provides an experimental study into the use of multi-wavelength sinusoidal leading edge ( LE) serrations for enhancing the aerofoil-broadband noise reductions. The noise reduction performances of multi-wavelength serration profiles introduced on a flat plate are compared against those generated by single-wavelength profiles when applied separately. The multi-wavelength leading edge serration is made in such a way that its maximum amplitude is kept same as that of each single-wavelength ones to be compared. The present study reveals that the dual-wavelength serrations provide higher noise reductions over a narrow band of frequencies as compared to single and triple wavelength ones. Further, it reveals that the noise reduction characteristics of dual-wavelength serrated airfoils are similar to the flat plates. It shows that the baseline plate generate higher noise radiations for all emission angles as compared to leading edge serrated plates, but the common feature among them is the downstream directivity. For the range of frequencies 0.9 to 5 kHz, the highest directivity is seen at an emission angle of 55° for the baseline, while it occurs at 75° for the serrated plates. The dual wavelength serrations generate lowest acoustic radiations as compared to single and triple ones for all the emission angles. Also, it is noticed that the radiation levels of the dual serrations decrease with increase in amplitude of the serration, which shows that the longer dual serrations generate lowest acoustic radiations. Thus, the present study illustrates that the dual wavelength leading edge serrations act as the best passively modified serration profiles for achieving the highest noise reductions over a wide range of frequencies as compared to single and triple wavelength ones.

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Shockwave and Noise Abatement of Transonic Fans

Volume 5: Turbo Expo 2004, Parts A and B ◽

10.1115/gt2004-53545 ◽

2004 ◽

Cited By ~ 2

Author(s):

Liping Xu

Keyword(s):

Shock Wave ◽

Noise Reduction ◽

Three Dimensional ◽

Leading Edge ◽

Aerodynamic Performance ◽

Test Results ◽

Shock Strength ◽

Noise Levels ◽

Noise Abatement ◽

Blade Passage

The aerodynamic sources of the forward tone noise of transonic civil fans are analysed. The leading edge shockwave near the rotor tip section is identified as the main source of tone noise. By comparing the tone noise levels of the same fan operating at two different working lines, numerical calculations show that on the lower working line, the main passage shockwave is swallowed and locked into the blade passage, and the fan blades act as a shield to prevent the strong passage shock wave from propagating upstream. The calculations show that, by running the fan at a lower working line, up to 6 db abatement in the blade passing frequency (BPF) tone can be achieved through shielding the shockwave. With three dimensional CFD it is possible to design swept rotors which have desired shockwave structures near the tip region. Fan rotors with different swept leading edges have been designed to study this effect and comparisons in aerodynamics performances as well as the tone noise levels are made. It is predicted that in a swept rotor the leading edge shock strength can be further weakened and up to 5db further reduction in tone noise is possible. With a more secure shockwave shielding, a forward swept rotor has the combination of better aerodynamic performance and better noise abatement feature. The design and test results of a three dimensional fan rotor LNR2, featuring localised forward swept rotor are presented. Rig test results show that although the noise reduction through shock shielding has been demonstrated, the aerodynamics and noise are complicated by the problems specific to such localised forward swept fan.

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Low Noise FEGV Designed by Numerical Method Based on CFD

Volume 5: Turbo Expo 2004, Parts A and B ◽

10.1115/gt2004-53239 ◽

2004 ◽

Cited By ~ 3

Author(s):

Naoki Tsuchiya ◽

Yoshiya Nakamura ◽

Shinya Goto ◽

Hidekazu Kodama ◽

Osamu Nozaki ◽

...

Keyword(s):

Noise Reduction ◽

Guide Vane ◽

Three Dimensional ◽

Leading Edge ◽

High Amplitude ◽

Aerodynamic Performance ◽

Low Noise ◽

Test Facility ◽

Noise Sources ◽

Fan Noise

This paper describes a low noise FEGV (Fan Exit Guide Vane), which is designed by a fan noise prediction method based on CFD. Fan noise is predicted by a hybrid scheme, which is the combination of three-dimensional CFD and three-dimensional linear theory. Characteristics of noise sources are investigated in some kinds of FEGV shapes. High amplitude areas spread not only along the leading edge but also in the span-wise positions along the mid-chord. It is found that high amplitude areas around the mid-chord make an important role in noise generation, and appropriate aft-ward swept angle and span-wise distribution of leaned angle could reduce the amplitude of the noise sources keeping aerodynamic performance. A fan noise test for fan scale models has been conducted at an anechoic test facility in IHI Mizuho to demonstrate noise reduction and performance of low noise FEGV. Noise reduction can be achieved keeping aerodynamic performance compared to conventional straight FEGV.

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Experimental Study of the Space–Time Effect of a Double-Pipe Frozen Curtain Formation with Different Groundwater Velocities

Energies ◽

10.3390/en14133830 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3830

Author(s):

Shicheng Sun ◽

Chuanxin Rong ◽

Hua Cheng ◽

Bin Wang ◽

Xiaogang Jiang ◽

...

Keyword(s):

Freezing Temperature ◽

Physical Model Test ◽

Sand Layer ◽

Test Results ◽

Groundwater Velocity ◽

Test Platform ◽

The Difference ◽

Freezing Test ◽

Double Pipe ◽

Thermal Physical Properties

Groundwater velocity has significant effects on the formation of a frozen curtain during freezing. In order to study the influence of the velocity on a frozen curtain, a large physical model test platform was established for double-pipe freezing. Based on this platform, freezing tests for different velocities were carried out. Quartz sand was selected as a similar material. The freezing temperature of the saturated sand layer was found by analyzing the results of the nuclear magnetic resonance (NMR). Based on the study of the thermal physical properties of the sand layer, the freezing test results were analyzed, and the results showed that the flow led to the differential development of the temperature between the upstream and downstream sections of the freezing pipes. Moreover, the larger the velocity, the greater the difference. The flow prolonged the overlapping time of the frozen curtains. Additionally, the flow slowed down the development of the frozen curtain area and the frozen curtain thickness. The larger the flow velocity, the greater the inhibition of the flow on the development of the frozen curtain. The test results can provide more references for the design and construction of freezing engineering with flowing groundwater.

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The Research of IC Test Based on LTX-77 Test System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.496-500.1176 ◽

2014 ◽

Vol 496-500 ◽

pp. 1176-1179

Author(s):

Li Tan ◽

Yu Fang

Keyword(s):

Test Object ◽

Test System ◽

Test Method ◽

Test Results ◽

Analog Ic ◽

Test Platform ◽

Logic Functions ◽

Actual Test ◽

Ic Test

LTX-77 test system is a large IC test system that is used for various kinds of analog IC, digital IC and analog digital mixed IC. It can be used to test DC parameters, AC parameters and logic functions. In the paper, the IC test platform is LTX-77 test system. IC ADC0804 was tested as the test object. The test method of IC is described in the view of actual test. The test results show that the test system is convenient and accurate, which has important practical value for IC manufacturers and users.

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An anti-crystallization design of selective catalytic reduction nozzle holder

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407020970848 ◽

2021 ◽

pp. 095440702097084

Author(s):

Dewen Liu ◽

Kai Lu ◽

Shusen Liu ◽

Yan Wu ◽

Shuzhan Bai

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Injection System ◽

Test Results ◽

Verification Methods ◽

Crystallization Risk ◽

Protective Cover ◽

Computational Fluid Dynamics Cfd ◽

Cfd Method ◽

Good Agreement

From the aspect of reducing the risk of crystallization on nozzle surface, a new design of nozzle protective cover was to solve the problem in selective catalytic reduction (SCR) urea injection system. The simulation calculation and experimental verification methods were used to compare different schemes. The results show that reducing the height of nozzle holder can reduce the vortex currents near nozzle surface and effectively reduce the risk of crystallization on the nozzle surface. It is proposed to install a protective cover in the nozzle holder under the scheme of reducing the height of nozzle holder, which can further eliminate the vortex. Simulation and test results demonstrate good agreement under the rated running condition. The scheme of adding a protective cover in the nozzle holder shows the least crystallization risk by computational fluid dynamics (CFD) method. The crystallization cycle test shows that, after the height of nozzle holder is reduced, the risk of crystallization on the nozzle surface is reduced correspondingly. The addition of a protective cover in the nozzle holder solves the problem of crystallization on the nozzle surface, which provides a new method for anti-crystallization design.

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Spanwise varying porosity for the enhancement of leading-edge noise reduction

AIAA AVIATION 2021 FORUM ◽

10.2514/6.2021-2191 ◽

2021 ◽

Author(s):

Lorna J. Ayton ◽

Orestis Karapiperis ◽

Manuj Awasthi ◽

Danielle Moreau ◽

Con J. Doolan

Keyword(s):

Noise Reduction ◽

Leading Edge

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Comparison of Noise Reduction Performance Evaluation Methods for Low-Noise Pavement in Korea- Part

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

10.3397/in-2021-2260 ◽

2021 ◽

Vol 263 (4) ◽

pp. 2930-2939

Author(s):

Byungchae Kim ◽

Hyunjin Kim ◽

Wonuk Kang

Keyword(s):

Noise Reduction ◽

Noise Level ◽

Measurement Method ◽

Road Traffic ◽

Low Noise ◽

Management Standards ◽

Close Proximity ◽

Porous Pavement ◽

Reduction Effect ◽

Measurement Location

In Korea, road noise is assessed as a measurement method of exterior noise emitted by road vehicle for management standards by the National Institute of Environmental Sciences. In this method, the noise felt at the actual pickup point is measured as LAeq (the roadside equivalent noise level). Recently, to clarify the standard for measuring noise on low-noise pavements, the CPX (ISO11819-2; Close-proximity method) was first introduced in the Porous Pavement Guidelines of the Ministry of Land, Infrastructure and Transport. According to ISO, the CPX adopts the side microphone as a mandatory measurement location, and the rear optional. The side location has been a mandatory due to its high correlation with SPB (ISO 11819-1, Statistical Pass-by method). However, according to our previous study on the correlation evaluation between L and CPX rear microphone noise level, both noise reduction effect was about 9-12 dB(A) showed a high correlation in Korea where heavy road traffic is common. The following study aims to show the consistent correlation between the L and CPX rear noise level. Furthermore, it is intended to be helpful in selecting the location of the CPX microphone that can most effectively represent the actual noise on the low-noise pavement in Korea.

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