scholarly journals A Design Study of Aerodynamic Noise Reduction In Centrifugal Compressor Part II . Low-noise Optimization Design

2004 ◽  
Vol 14 (10) ◽  
pp. 939-944 ◽  
Keyword(s):  
Noise Reduction ◽  
Centrifugal Compressor ◽  
Optimization Design ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Design Study ◽  
Noise Optimization

scholarly journals Research on Aerodynamic Noise Reduction for High-Speed Trains

2016 ◽  
Vol 2016 ◽  
pp. 1-21 ◽  
Author(s):  
Yadong Zhang ◽  
Jiye Zhang ◽  
Tian Li ◽  
Liang Zhang ◽  
Weihua Zhang
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Low Noise ◽  
Broadband Noise ◽  
Full Scale ◽  
Noise Model ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Noise Sources

A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H) acoustic analogy. An analysis of noise reduction methods based on the main noise sources was performed. An aerodynamic noise model for a full-scale high-speed train, including three coaches with six bogies, two inter-coach spacings, two windscreen wipers, and two pantographs, was established. Several low-noise design improvements for the high-speed train were identified, based primarily on the main noise sources; these improvements included the choice of the knuckle-downstream or knuckle-upstream pantograph orientation as well as different pantograph fairing structures, pantograph fairing installation positions, pantograph lifting configurations, inter-coach spacings, and bogie skirt boards. Based on the analysis, we designed a low-noise structure for a full-scale high-speed train with an average sound pressure level (SPL) 3.2 dB(A) lower than that of the original train. Thus, the noise reduction design goal was achieved. In addition, the accuracy of the aerodynamic noise calculation method was demonstrated via experimental wind tunnel tests.

Effects analysis on aerodynamic noise reduction of centrifugal compressor used for gasoline engine

2021 ◽  
Vol 180 ◽  
pp. 108104
Author(s):  
Chao Zhong ◽  
Liaoping Hu ◽  
Jinke Gong ◽  
Chenxi Wu ◽  
Shaoli Wang ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Centrifugal Compressor ◽  
Gasoline Engine ◽  
Aerodynamic Noise

scholarly journals Numerical Investigation of Aerodynamic Noise Reduction of Nonpneumatic Tire Using Nonsmooth Riblet Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Haichao Zhou ◽  
Zhen Jiang ◽  
Jian Yang ◽  
Huihui Zhai ◽  
Guolin Wang
Keyword(s):  
Noise Reduction ◽  
Transient Flow ◽  
Pressure Coefficient ◽  
Rolling Resistance ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Noise Sources ◽  
Vortex Theory ◽  
Study Results ◽  
Riblet Surface

Unlike conventional pneumatic tires, the nonpneumatic tires (NPT) are explosion proof and simple to maintain and provide low rolling resistance. At high vehicle speeds, however, the complex airflow produced by the open flexible-spoke structure of NPT yields high aerodynamic noise, which contributes to sound pollution in the vehicular traffic environment. Inspired by the idea that a nonsmooth riblet structure can affect fluid flow and offer noise reduction, the analyses of the effect of the nonsmooth riblet surface on the aerodynamic noise of an NPT and noise reduction mechanism were presented in this paper. First, computational fluid dynamics (CFD) was used to analyze the surface pressure coefficient characteristics of a smooth flexible-spoke tire rolling at a speed of 80 km/h and subsequently validating the numerical simulation results by comparing them with published test results. Secondly, large eddy simulation (LES) and the Ffowcs Williams–Hawkings (FW-H) method were, respectively, used to determine the transient flow and far-field aerodynamic noise. Then, the mechanism of noise reduction was investigated using a vortex theory. Based on the vortex theory, the positions and strengths of noise sources were determined using the Lamb vector. Finally, according to the fluid boundary layer theory, a nonsmooth riblet surface was arranged on the surface of the spokes, and the influences of the riblet structure parameters, including size, position, and direction, on aerodynamic noise were analyzed. Based on the vortex theory, it was found that the nonsmooth riblet structure can reduce the Lamb vector, suppress the generation of flow vortices, decrease acoustic source strength, and effectively decrease noise up to 5.18 dB using the optimized riblet structure. The study results provide a theoretical basis for the structural design of a new low-noise NPT.

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.

Aerodynamic noise reduction by pile fabrics

2010 ◽  
Vol 42 (1) ◽  
pp. 015003 ◽  
Author(s):  
Masaharu Nishimura ◽  
Tomonobu Goto
Keyword(s):  
Noise Reduction ◽  
Aerodynamic Noise

Optimization of Low Noise Blade of Small Axial Fan at Low Reynolds Number

2021 ◽  
Vol 263 (6) ◽  
pp. 236-256
Author(s):  
Peixun Yu ◽  
Junqiang Bai ◽  
Xiao Han
Keyword(s):  
Sound Pressure Level ◽  
Optimization Design ◽  
Sound Pressure ◽  
Computational Cost ◽  
Low Noise ◽  
Pressure Level ◽  
Multidisciplinary Optimization ◽  
Axial Fan ◽  
Aerodynamic Efficiency ◽  
Cooling Fan

A multidisciplinary optimization design to simultaneously enhance the aeroacoustic and aerodynamic performance of an cooling fan is performed. The flow analysis of the cooling fan is conducted by solving three dimensional steady-state RANS equations with shear-stress transport turbulence model. Based on the results of the steady flow, aeroacoustic analysis is performed by using the Hanson and Brooks model. A multi-objective optimization is performed to simultaneously improve the efficiency and reduce the sound pressure level through an improved non-dominated sorting gentic algorithm. A Kriging surrogate model is used to approximate the function value while reducing computational cost. Series of optimum designs on the pareto front yielded increases in efficiency and decreases in the sound pressure level compared to the reference design. Through numerical analysis and experimental test, the aerodynamic efficiency is increased by 5% and the total sound pressure level is reduced by 4dB without loss of air volume for the selected optimized cooling fan. The thining of rotor boundary layer and inward load shift are the main factors to improve aerodynamic efficiency and reduce noise of the cooling fan.

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

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.

Sign in / Sign up

Export Citation Format

Share Document