scholarly journals Aerodynamic noise radiating from the inter-coach windshield region of a high-speed train

2018 ◽  
Vol 37 (3) ◽  
pp. 590-610 ◽  
Author(s):  
Wen-Qiang Dai ◽  
Xu Zheng ◽  
Zhi-Yong Hao ◽  
Yi Qiu ◽  
Heng Li ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Near Field ◽  
Acoustic Power ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Dominant Factor ◽  
High Speed Train ◽  
Frequency Range

The aerodynamic noise has been the dominant factor of noise issues in high-speed train as the traveling speed increases. The inter-coach windshield region is considered as one of the main aerodynamic noise sources; however, the corresponding characteristics have not been well investigated. In this paper, a hybrid method is adopted to study the aerodynamic noise around the windshield region. The effectiveness of simulation methods is validated by a simple case of cavity noise. After that, the Reynolds-averaged Navier–Stokes simulation is used to obtain the characteristics of flow field around the windshield region, which determine the aerodynamic noise. Then the nonlinear acoustic solver approach is employed to acquire the near-field noise, while the Ffowcs-Williams/Hawking equation is solved for far-field acoustic propagation. The results indicate that the windshield region is approximately an open cavity filled with severe disturbance flow. According to the analysis of sound pressure distribution in the near-acoustic field, both sides of the windshield region appear symmetrical two-lobe shape with different directivities. The results of frequency spectrum analysis indicate that the aerodynamic noise inside inter-coach space is a typical broadband one from 100 Hz to 5k Hz, and most acoustic power is restricted in the low-medium frequency range (below 500 Hz). In addition, the acoustic power in the low frequency range (below 100 Hz) is closely related to the cavity resonance with the resonance peak frequency of 42 Hz. The overall sound pressure level at different speeds shows that the acoustic power grows approximately 5th power of the train speed. Two forms of outside-windshields are designed to reduce the noise around the windshield region, and the results show the full-windshield form is better in noise reduction, which apparently eliminates interior cavity noise of inter-coach space and lessens the overall sound pressure level on the sides of near-field by about 13 dB.

Shape Optimization of High-Speed Train Pantograph Insulators for Low Aerodynamic Noise

2012 ◽  
Vol 249-250 ◽  
pp. 646-651
Author(s):  
Xiao Yan Yang ◽  
You Gang Xiao ◽  
Yu Shi
Keyword(s):  
Shape Optimization ◽  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Elliptical Section

With large eddy simulation(LES) and Lighthill-Curle acoustic theory, the aerodynamic noises radiated from pantograph insulators with rectangular, circular, elliptical section were calculated, and the optimal pantograph insulator shape was obtained. The results show that in the same model, the sound pressure level (SPL) spectrum at different monitoring points are basically the same, but the amplitude is different. In different models, the SPL spectrum are different. As for rectangular, circular, elliptical section insulators, the frequency with maximum SPL reduces gradually. For reducing aerodynamic noise, the elliptical section insulator is optimal, and the long elliptical axis should be consistent with air flow. The pantograph with bigger and less components is helpful to reduce the aerodynamic noise.

Analysis of the Influence of Racks on High Speed Train Interior Noise Using Finite Element Method

2014 ◽  
Vol 675-677 ◽  
pp. 257-260 ◽  
Author(s):  
Di Wu ◽  
Jian Min Ge
Keyword(s):  
Finite Element ◽  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Low Frequency ◽  
Sound Field ◽  
Pressure Level ◽  
High Speed Train ◽  
Fe Method ◽  
Proposed Model

In this paper, the finite element (FE) method was used for simulation of the low-frequency sound field in high speed train compartments. The proposed model was validated using experimental results. The FE models of the train compartments with and without racks were established respectively, and the sound pressure level of the standard point and sound field distribution in these two cases were compared. The results showed that the A-weighted sound pressure level of the standard point was 1.2 dB lower when there is no rack in the compartment.

Research on Aerodynamic Noise of Base Styling Characteristics of Car Rearview Cover

2012 ◽  
Vol 490-495 ◽  
pp. 2987-2991
Author(s):  
Xin Chen ◽  
Jun Long Zhou
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Interior Noise ◽  
Aerodynamic Noise ◽  
Theory Of Computation ◽  
Frequency Range ◽  
Digital Models ◽  
Compare Analysis

The 3-D digital models are established for two kinds of base styling of rearview cover. The compare analysis using Fluent model is based on the acoustic theory of computation. The results show that the average sound pressure level of up-raised rearview cover model is about 5 dB lower than that down-raised rearview cover model, and in all of the frequency range were apparently different. At the same time, the vortex of down-raised happened at the back location, which is more closer to the passenger’s ear, and affect the car interior noise. The results of analysis will conduct the design of rearview styling effectively.

scholarly journals Complexity Study on the Unsteady Flow Field and Aerodynamic Noise of High-Speed Railways on Bridges

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Jufeng Su ◽  
Yamin Sun ◽  
Yuyang Liu
Keyword(s):  
Unsteady Flow ◽  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Pressure Level ◽  
Noise Model ◽  
Aerodynamic Noise ◽  
High Speed Railway ◽  
Wake Flows ◽  
Flat Ground

To study complexity distributions of unsteady flow field and aerodynamic noise of a high-speed railway on bridges, an aerodynamic noise model of a railway was obtained. Meanwhile, detailed structures such as 6 bogies, 3 air conditioning units, 1 pantograph fairing, and 1 pantograph were considered. Numerical simulation was conducted to flow fields around the high-speed railway running on the bridge under a crosswind-free environment, with running speed of 350 km/h. Hence, unsteady flow behavior characteristics of the complete high-speed railway were obtained. Numerical simulation was conducted to noises of the railway on the bridge in combination with detached eddy simulation and acoustic analogy theory. Meanwhile, the broadband noise model was used for the quantitative analysis on distribution characteristics of the dipole noise source and quadrupole noise source of the high-speed railway on the bridge. Studied results proved that aerodynamic noise of the railway was caused by eddy shedding and fluid separation. Main noise sources of the high-speed railway include areas such as pantographs, train head streamline, bogies, windshield, and an air conditioning unit. Maximum sound pressure level and average sound pressure level of the high-speed railway on the bridge were 2.7 dBA and 2.3 dBA, respectively, more than those of the high-speed railway on a flat ground. On the bridge, the maximum sound pressure level of the pantograph on the bridge was 3.1 dBA larger than that on the flat ground. In addition, incoming flows of the high-speed railway on the bridge had greater impacts on aerodynamic noises around the railway compared with those of wake flows. Meanwhile, in directions of incoming flows and wake flows, linear relationship was between the sound pressure levels of noise monitoring points which had different distances from the train head nose and the logarithm of the distances.

scholarly journals Numerical simulation of the slipstream and aeroacoustic field around a high-speed train

2016 ◽  
Vol 231 (6) ◽  
pp. 740-756 ◽  
Author(s):  
Chunli Zhu ◽  
Hassan Hemida ◽  
Dominic Flynn ◽  
Chris Baker ◽  
Xifeng Liang ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Broadband Noise ◽  
Full Scale ◽  
High Speed Train ◽  
Noise Characteristics ◽  
Simulation Results

The flow field and sound propagation around a three-coach 1/8th scale high-speed passenger train were obtained using a detached-eddy simulation and the Ffowcs-Williams and Hawkings acoustic analogy. The Reynolds number of flow based on the train height and speed was 2,000,000. The numerical results of the flow and aeroacoustic fields were validated using wind tunnel experiments and full-scale data, respectively. Features of overall sound pressure level, sound pressure level and A-weighted sound pressure level of typical measuring points are discussed. The sound propagated by a high-speed train is shown as a broadband noise spectrum including tonal component, where high sound pressure levels are concentrated on the low-frequency range from 10 Hz to 300 Hz. The inter-carriage gap is found to cause distinct tonal noise in contrast to the other parts of the train that cause a broadband noise. The negative log law has been used to study the influence of distance from the centre of track on the sound pressure level, where a good fit is shown at low-frequency ranges. The peak values of A-weighted sound pressure level from both full-scale experiment and simulation results occur at approximately 1 kHz, where simulation results show almost the same range as the experiment. The surface of each component of the train as well as the whole train are chosen as the integral surface for the Ffowcs-Williams and Hawkings computation of the far-field noise characteristics. It was found that the sound source generated by a high-speed train is mainly dipole, and the largest noise was obtained from the leading bogie. The results of this paper provide, for the first time, a better understanding of the aeroacoustic field around a three-coach train model, and the paper has the potential to assist engineers to design high-speed trains with aeroacoustic noise reduction in a better manner.

Numerical investigation of aerodynamic and acoustic characteristics of bionic airfoils inspired by bird wing

2018 ◽  
Vol 233 (11) ◽  
pp. 4004-4016 ◽  
Author(s):  
Menghao Wang ◽  
Xiaomin Liu
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Leading Edge ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Small Scale ◽  
Airfoil Surface ◽  
Acoustic Characteristics ◽  
Bionic Coupling ◽  
Bionic Airfoil

Airfoil is the basic element of fluid machinery and aircraft, and the noise generated from that is an important research aspect. Aiming to reduce the aerodynamic noise around the airfoil, this study proposes an airfoil inspired by the long-eared owl wing and another airfoil coupled with the bionic airfoil profile, leading edge waves, and trailing edge serrations. Numerical simulations dependent on the large eddy simulation method coupled with the wall-adapting local eddy-viscosity model and the Ffowcs Williams and Hawkings equation are conducted to compare the aerodynamic and acoustic characteristics of two types of bionic airfoils at low Reynolds number condition. The simulations reveal the dipole characteristic of acoustic source and sound pressure level distribution at various frequencies. Two types of bionic airfoils show lower noise compared with the conventional NACA 0012 airfoil with a similar relative thickness of 12%. Compared with the bionic airfoil, the average value of sound pressure level at the monitoring points around the bionic coupling airfoil is decreased by 9.94 dB, meanwhile the lift-to-drag ratio also keep higher. The bionic coupling airfoil exerts a suppression of sound pressure fluctuation on the airfoil surfaces, which result from that the range and size of separation vortices are reduced and the distance between vortices and airfoil surface are increased. The tube-shaped vortices in the wake of airfoil are effectively restrained and split into small scale vortices, which are important to cause less aerodynamic noise around the bionic coupling airfoil. Consequently, a novel bionic coupling airfoil is developed with the excellent aerodynamic and acoustic performance.

scholarly journals Supersonic Windtunnel Noise Attenuation

2021 ◽  
Author(s):  
William Wai Lim Wong
Keyword(s):  
Wind Tunnel ◽  
Sound Pressure Level ◽  
Noise Level ◽  
Sound Pressure ◽  
Power Level ◽  
Mesh Size ◽  
Acoustic Power ◽  
Pressure Level ◽  
Supersonic Wind Tunnel ◽  
Acoustic Treatment

The aerodynamic generated noise in the supersonic wind tunnel during operation at Ryerson University has exceeded the threshold of hearing damage. An acoustic silencer was to be designed and added to the wind tunnel to reduce the noise level. The main sources of noise generated from the wind tunnel with the silencer were identified to be located at the convergent divergent nozzle and the turbulent region downstream of the shock wave at the diffuser with the maximum acoustic power level of the entire wind tunnel at 161.09 dB. The designed silencer provided an overall sound pressure level reduction of 21.41 db which was considered as acceptable. Refinement to the mesh size and changes to the geometry of the mixing chamber was suggested for a more accurate result in noise output as well as flow conditions would match up to the physical flow. Additional acoustic treatment should be applied to the wind tunnel to further reduce sound pressure level since the noise level still exceeded the threshold of hearing loss.

Effect of Pantograph and Bogie on Interior Noise of High-Speed Train in Tunnel

2013 ◽  
Vol 664 ◽  
pp. 191-196
Author(s):  
You Gang Xiao ◽  
Yu Shi
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Broad Band ◽  
Pressure Level ◽  
Channel Noise ◽  
High Speed Train ◽  
Noise Sources ◽  
Vehicle Noise ◽  
Measurement And Analysis ◽  
Analysis System

For clarifying the noise in tunnel affected by pantograph and bogie, which are the most important noise sources, the noises near pantograph and bogie in a high-speed train were tested by multi-channel noise measurement and analysis system in tunnel, and compared with those measured outside the High-speed train and on an open field. The results show that the interior vehicle noise is spatially non-homogeneous in the whole carriage, the larger sound pressure level (SPL) near pantograph are next to ceiling, and near bogie next to floor. The noise spectra show a broad band feature, and dominated by the frequency contents among 100Hz-2kHz, so the countermeasures against noise should be within these range.

scholarly journals Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10–40 kHz frequency range

2020 ◽  
Vol 18 (2) ◽  
pp. 1451-1463
Author(s):  
Witold Mikulski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sheet Steel ◽  
Pressure Level ◽  
Sound Insulation ◽  
Frequency Range ◽  
Noise Sources ◽  
Human Environment ◽  
Absorbing Material ◽  
Acoustic Enclosures

Abstract Purpose The purpose of the research is to work out a method for determining the sound insulation of acoustic enclosures for industrial sources emitting noise in the frequency range of 10–40 kHz and apply the method to measure the sound insulation of acoustic enclosures build of different materials. Methods The method is developed by appropriate adaptation of techniques applicable currently for sound frequencies of up to 10 kHz. The sound insulation of example enclosures is determined with the use of this newly developed method. Results The research results indicate that enclosures (made of polycarbonate, plexiglass, sheet aluminium, sheet steel, plywood, and composite materials) enable reducing the sound pressure level in the environment for the frequency of 10 kHz by 19–25 dB with the reduction increasing to 40–48 dB for the frequency of 40 Hz. The sound insulation of acoustic enclosures with a sound-absorbing material inside reaches about 38 dB for the frequency of 10 kHz and about 63 dB for the frequency of 40 kHz. Conclusion Some pieces of equipment installed in the work environment are sources of noise emitted in the 10–40 kHz frequency range with the intensity which can be high enough to be harmful to humans. The most effective technical reduction of the associated risks are acoustic enclosures for such noise sources. The sound pressure level reduction obtained after provision of an enclosure depends on its design (shape, size, material, and thickness of walls) and the noise source frequency spectrum. Realistically available noise reduction values may exceed 60 dB.

Experimental and Numerical Investigation of Blades Effect on Aerodynamic Performance of Small Axial Flow Fan

2011 ◽  
Author(s):  
Li Zhang ◽  
Yingzi Jin ◽  
Yi Zhao ◽  
Pin Liu
Keyword(s):  
Flow Field ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Blade Number ◽  
Small Axial Flow Fan ◽  
Fan Blade

To explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, the steady flow field and the unsteady flow field of fan models with 6 different blade numbers (such as 5, 7, 9, 11, 13, 15) are numerically calculated. Then the internal flow distribution, static characteristic and aerodynamic noise are analyzed among six different fan models. The analysis results show: (1)Total pressure and efficiency generally maintain the trend of first increasing and then decreasing with increasing blade numbers, and it is the maximum when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With increasing blade numbers, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is first decreasing and then increasing before decreasing again at 1 meter away from the central axis of the impeller along the outlet. When fan blade number is 11, overall sound pressure level of the aerodynamic noise is the greatest. Furthermore, the aerodynamic performance tests of fan models with 6 different blade numbers are carried out, the results of between the tests and the numerical calculations are roughly consistent. The research results will provide the proof of the parameter optimization and the structure design for high performance and low noise small axial fans.

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