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.

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.

Numerical prediction of aerodynamic noise from impeller blowers of straw threshing machines

2019 ◽  
Vol 51 (1-2) ◽  
pp. 21-32
Author(s):  
Zhai ZhiPing ◽  
Li ZhuWei ◽  
Zhang Long ◽  
Yang Zhongyi ◽  
Lan Yuezheng
Keyword(s):  
Unsteady Flow ◽  
Sound Pressure Level ◽  
Optimization Design ◽  
Sound Pressure ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Dipole Source ◽  
Discrete Phase Model ◽  
Full Field ◽  
Rotating Impeller

An impeller blower is one of the major aerodynamic noise sources in straw threshing machines. To reduce its aerodynamic noise, it is essential to understand the mechanism of gas-material-coupled unsteady flow causing aerodynamic noise. However, it is difficult to clarify the mechanism through measurement. Therefore, the following topics are studied in this article. First, a full-field transient numerical simulation of the gas and solid particulates’ unsteady flow inside the impeller blower was carried out using a dense discrete phase model and a large eddy simulation turbulence model. Second, based on the Ffowcs Williams–Hawkins equation, the aerodynamic noise of the impeller blower of the straw threshing machines was numerically calculated. Finally, the numerical results were verified by aerodynamic noise test. The results indicate that (1) sound pressure level at the inlet of the impeller blower is the highest, mainly at 100 Hz, which is the fundamental frequency of the rotating impeller, while the sound pressure level at the fourth harmonic frequency of 400 Hz is the main source of the outlet. The total sound pressure level at the inlet is greater than that at the outlet. It is concluded that the dipole source of the rotating impeller is the main noise source, which was generated by the interaction of blade with the air and material as the impeller rotated. Also, acoustic attenuation, acoustic resonance, and impact noise of material and machinery play important roles in aerodynamic noise distribution. (2) The test and simulation results show good agreement, so the numerical model of aerodynamic noise is reliable. This study will provide a reference for the structural and acoustic optimization design of impeller blowers and their integration into threshing machines.

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.

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.

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.

Grid Requirements for Multiscale Resolution in Separated Unsteady High Speed Turbulent Flows

2006 ◽  
Author(s):  
D. Basu ◽  
A. Hamed ◽  
K. Das
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulent Flows ◽  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Pressure Fluctuations ◽  
Pressure Level ◽  
Navier Stokes ◽  
Detached Eddy Simulation

This study deals with the computational grid requirements in multiscale simulations of separated turbulent flows at high Reynolds number. The two-equation k-ε based DES (Detached Eddy Simulation) model is implemented in a full 3-D Navier-Stokes solver and numerical results are presented for transonic flow solution over an open cavity. Results for the vorticity, pressure fluctuations, SPL (Sound Pressure level) spectra and for modeled and resolved TKE (Turbulent Kinetic Energy) are presented and compared with available experimental data and with LES results. The results indicate that grid resolution significantly influences the resolved scales and the peak amplitude of the unsteady sound pressure level (SPL) and turbulent kinetic energy spectra.

Influence of Crosswind to Automobile Interior Aerodynamic Noise

2012 ◽  
Vol 503-504 ◽  
pp. 1164-1168
Author(s):  
Yin Zhi He ◽  
Zhi Gang Yang
Keyword(s):  
Sound Pressure Level ◽  
Pressure Fluctuation ◽  
Sound Pressure ◽  
Window Glass ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Vehicle Interior ◽  
Side Window ◽  
Transmission Mechanisms ◽  
Yaw Angle

After a brief introduction about aerodynamic noise generation and transmission mechanisms, the influence of crosswind to vehicle interior aerodynamic noise for a production automobile sedan was investigated through full-scale aeroacoustic wind tunnel tests. Through analysis of sound pressure level of vehicle interior driver ear position and pressure fluctuation level on vehicle side window glass under different yaw angles, the following results are obtained: The frequency characteristics of vehicle interior aerodynamic noise vary as yaw angle changes under one certain wind speed. Whether on the leeside or by windward, sound pressure level increases as yaw angle goes up. Under the same yaw angle, interior noise level on the leeside is higher than that by windward. Test results between pressure fluctuation level on side window glass and vehicle interior aerodynamic noise of driver ear position show good correlation

Effect of Blade Numbers on Aerodynamic Performance and Noise of Small Axial Flow Fan

2011 ◽  
Vol 199-200 ◽  
pp. 796-800
Author(s):  
Li Zhang ◽  
Ying Zi Jin
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 more fully explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, some solutions are adopted to obtain the parameters’ distribution of the flow field.Firstly, the standard k-ε turbulence model is used to calculate the steady flow field of six different fan blades(such as 5,7,9,11,13,15) , and the SIMPLE algorithm is applied to couple vecolity and pressure. Secondly, the large eddy simulation in conjunction with the FH-W noise model are used to compute the unsteady flow field and noise. Finally, the experimental results verify that the calculation methods of steady flow field and unsteady flow field are correct. The conclusions show: (1)Total pressure and efficiency generally maintain the trend of firstly increasing and then decreasing with increasing the blade numbers, and it is the greatest when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With the increasing blades, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is firstly decreasing and then increasing before decreasing again 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.

scholarly journals Experimental study of aerodynamic noise performance of improved air distributor for ships

2021 ◽  
Vol 13 (3) ◽  
pp. 168781402110012
Author(s):  
Yuejiao Guo ◽  
Guozeng Feng ◽  
Shuya Lei ◽  
Bo Meng ◽  
Yang Xu
Keyword(s):  
Flow Rate ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Static Pressure ◽  
Resistance Coefficient ◽  
Pressure Level ◽  
Channel Structure ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Reduction Effect

In ships, aerodynamic noise from the variable-air-volume fan is a common problem. This study experimentally explores the strategy of reshaping the traditional C-shaped channel structure to an L-shape to reduce noise. The noise level and resistance coefficient of the improved air distributor are analysed, and the results show that the noise of the original air distributor is 56.3 dB(A) under the rated working conditions (static pressure of 800 Pa and flow rate of 350 m3/h), which exceeds the International Maritime Organisation’s (IMO) ship noise limit (55 dB(A)). For the improved air distributor, the noise pressure level is 38.5 dB(A), the sound pressure level of high-frequency noise is reduced by 48% and the peak sound pressure level appears at 125 to 250 Hz, a frequency below the threshold of human hearing. Thus, the reshaping of the channel has a significant noise reduction effect. When the static pressure is 400 Pa and the flow rate is 100 to 500 m3/h, the sound pressure level of the improved air distributor is reduced by 29.9% to 32.2% to become less than 55 dB(A). Thus, the sound pressure level at the outlet of the improved air distributor meets the IMO ship noise standard.

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.

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