scholarly journals Numerical Modeling and Investigation on Aerodynamic Noise Characteristics of Pantographs in High-Speed Trains

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaoqi Sun ◽  
Han Xiao
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Sound Pressure ◽  
Noise Source ◽  
Flow Fields ◽  
Aerodynamic Noise ◽  
Far Field ◽  
Frequency Bands ◽  
Noise Characteristics ◽  
High Speed Trains

Pantographs are important devices on high-speed trains. When a train runs at a high speed, concave and convex parts of the train cause serious airflow disturbances and result in flow separation, eddy shedding, and breakdown. A strong fluctuation pressure field will be caused and transformed into aerodynamic noises. When high-speed trains reach 300 km/h, aerodynamic noises become the main noise source. Aerodynamic noises of pantographs occupy a large proportion in far-field aerodynamic noises of the whole train. Therefore, the problem of aerodynamic noises for pantographs is outstanding among many aerodynamics problems. This paper applies Detached Eddy Simulation (DES) to conducting numerical simulations of flow fields around pantographs of high-speed trains which run in the open air. Time-domain characteristics, frequency-domain characteristics, and unsteady flow fields of aerodynamic noises for pantographs are obtained. The acoustic boundary element method is used to study noise radiation characteristics of pantographs. Results indicate that eddies with different rotation directions and different scales are in regions such as pantograph heads, hinge joints, bottom frames, and insulators, while larger eddies are on pantograph heads and bottom frames. These eddies affect fluctuation pressures of pantographs to form aerodynamic noise sources. Slide plates, pantograph heads, balance rods, insulators, bottom frames, and push rods are the main aerodynamic noise source of pantographs. Radiated energies of pantographs are mainly in mid-frequency and high-frequency bands. In high-frequency bands, the far-field aerodynamic noise of pantographs is mainly contributed by the pantograph head. Single-frequency noises are in the far-field aerodynamic noise of pantographs, where main frequencies are 293 Hz, 586 Hz, 880 Hz, and 1173 Hz. The farther the observed point is from the noise source, the faster the sound pressure attenuation will be. When the distance of two adjacent observed points is increased by double, the attenuation amplitude of sound pressure levels for pantographs is around 6.6 dB.

Analysis of the near-field and far-field sound pressure generated by high-speed trains pantograph system

2020 ◽  
Vol 169 ◽  
pp. 107506
Author(s):  
Yue-ying Zhao ◽  
Zhi-gang Yang ◽  
Qi-liang Li ◽  
Chao Xia
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Near Field ◽  
Far Field ◽  
High Speed Trains ◽  
Field Sound

scholarly journals Aerodynamic Noise Characteristics of High-speed Trains by the Beamforming Method

2012 ◽  
Vol 15 (3) ◽  
pp. 231-236 ◽  
Author(s):  
Hee-Min Noh ◽  
Sung-Hoon Choi ◽  
Hyo-In Koh ◽  
Suk-Yoon Hong
Keyword(s):  
High Speed ◽  
Aerodynamic Noise ◽  
Noise Characteristics ◽  
High Speed Trains

The effect of streamwise vortices on the aeroacoustics of a Mach 0.9 jet

2007 ◽  
Vol 578 ◽  
pp. 139-169 ◽  
Author(s):  
MEHMET B. ALKISLAR ◽  
A. KROTHAPALLI ◽  
G. W. BUTLER
Keyword(s):  
Flow Field ◽  
Shear Layer ◽  
High Frequency ◽  
High Speed ◽  
Sound Pressure ◽  
Near Field ◽  
Stereoscopic Particle Image Velocimetry ◽  
Far Field ◽  
Streamwise Vortices ◽  
Uniform Noise

The role of the streamwise vortices on the aeroacoustics of a Mach 0.9 axisymmetric jet is investigated using two different devices to generate streamwise vortices: microjets and chevrons. The resultant acoustic field is mapped by sideline microphones and a microphone phased array. The flow-field characteristics within the first few diameters of the nozzle exit are obtained using stereoscopic particle image velocimetry (PIV). The flow-field measurements reveal that the counter-rotating streamwise vortex pairs generated by microjets are located primarily at the high-speed side of the initial shear layer. In contrast, the chevrons generate vortices of greater strength that reside mostly on the low-speed side. Although the magnitude of the chevron's axial vorticity is initially higher, it decays more rapidly with downstream distance. As a result, their influence is confined to a smaller region of the jet. The axial vorticity generated by both devices produces an increase in local entrainment and mixing, increasing the near-field turbulence levels. It is argued that the increase in high-frequency sound pressure levels (SPL) commonly observed in the far-field noise spectrum is due to the increase in the turbulence levels close to the jet exit on the high-speed side of the shear layer. The greater persistence and lower strength of the streamwise vortices generated by microjets appear to shift the cross-over frequencies to higher values and minimize the high-frequency lift in the far-field spectrum. The measured overall sound pressure level (OASPL) shows that microjet injection provides relatively uniform noise suppression for a wider range of sound radiation angles when compared to that of a chevron nozzle.

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

scholarly journals Source Contribution Analysis for Exterior Noise of a High-Speed Train: Experiments and Simulations

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jie Zhang ◽  
Xinbiao Xiao ◽  
Dewei Wang ◽  
Yan Yang ◽  
Jing Fan
Keyword(s):  
High Speed ◽  
Noise Source ◽  
High Speed Train ◽  
Noise Sources ◽  
Sound Sources ◽  
Lower Region ◽  
Source Contribution ◽  
Array Measurements ◽  
Noise Characteristics ◽  
Train Speed

This paper presents a detailed investigation into the contributions of different sound sources to the exterior noise of a high-speed train both experimentally and by simulations. The in situ exterior noise measurements of the high-speed train, including pass-by noise and noise source identification, are carried out on a viaduct. Pass-by noise characteristics, noise source localizations, noise source contributions of different regions, and noise source vertical distributions are considered in the data analysis, and it is shown how they are affected by the train speed. An exterior noise simulation model of the high-speed train is established based on the method of ray acoustics, and the inputs come from the array measurements. The predicted results are generally in good agreement with the measurements. The results show that for the high-speed train investigated in this paper, the sources with the highest levels are located at bogie and pantograph regions. The contributions of the noise sources in the carbody region on the pass-by noise increase with an increasing distance, while those in the bogie and train head decrease. The source contribution rates of the bogie and the lower region decrease with increasing train speed, while those of the coach centre increase. At a distance of 25 m, the effect of the different sound sources control on the pass-by noise is analysed, namely, the lower region, bogie, coach centre, roof region, and pantograph. This study can provide a basis for exterior noise control of high-speed trains.

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