scholarly journals Flow Visualization of Rear-view Mirror Surface for Identification of Aerodynamic Noise Source

2005 ◽  
Vol 25 (Supplement2) ◽  
pp. 189-192
Author(s):  
Nobuyoshi OGUMA ◽  
Akiyoshi IIDA ◽  
Ayumi KOKUBO
Keyword(s):  
Flow Visualization ◽  
Noise Source ◽  
Aerodynamic Noise ◽  
Mirror Surface ◽  
Rear View Mirror

Study of Low Frequency Aerodynamic Noise Source formed on an Automobile Door Mirror

2016 ◽  
Vol 2016 (0) ◽  
pp. 1202
Author(s):  
Yusuke SAKAMOTO ◽  
Soichi SASAKI ◽  
Hiroshi ISHIKAWA ◽  
Noriki IWANAGA
Keyword(s):  
Noise Source ◽  
Low Frequency ◽  
Aerodynamic Noise

Numerical Analysis of the Surface Aerodynamic Noise of the CRH3 High Speed Train

2014 ◽  
Vol 1044-1045 ◽  
pp. 643-649
Author(s):  
Ji Zhou Liu ◽  
Ren Xian Li ◽  
Peng Xiang Cui
Keyword(s):  
High Speed ◽  
Noise Source ◽  
Radiation Power ◽  
Spectral Characteristics ◽  
Radiation Energy ◽  
Simulation Method ◽  
Acoustic Power ◽  
Broadband Noise ◽  
Aerodynamic Noise ◽  
High Speed Train

For high speed trains running at 300km/h or more, the aerodynamic noise becomes the primary noise source. A good knowledge of the location, spectral characteristics and propagation behavior of the noise source and the corresponding methods to reduce the effect of the aerodynamic noise are of crucial necessity during the design process of the high speed train. Based on the Lighthill Analogy, the pressure fluctuation of air at the surface of the train is acquired by simulating the flow field of a CRH3 high speed train running at 200 km/h, 300 km/h, 400 km/h and 500km/h by means of large eddy simulation method. By Fourier transformation, the distribution and the spectral characteristics of the surface acoustic dipole sources are obtained. The analysis of the results shows that the aerodynamic noise of the high speed train is a broadband noise with a strong radiation power band from 50Hz to 1000Hz. The dipole acoustic power calculated by statistically averaged on train surface is found to be proportional to the sixth power of running speed of the high speed train. The first and second bogie, the inter-car gap, the air deflector of the power train and the train nose of the last wagon are the main noise sources that contain high radiation energy.

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.

scholarly journals Development of an Efficient Numerical Method for Wind Turbine Flow, Sound Generation, and Propagation under Multi-Wake Conditions

2018 ◽  
Vol 9 (1) ◽  
pp. 100 ◽  
Author(s):  
Zhenye Sun ◽  
Wei Zhu ◽  
Wen Shen ◽  
Emre Barlas ◽  
Jens Sørensen ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Numerical Method ◽  
Wind Turbines ◽  
Noise Source ◽  
Axisymmetric Flow ◽  
Wake Flow ◽  
Propagation Path ◽  
Aerodynamic Noise ◽  
Long Distance ◽  
Noise Propagation

The propagation of aerodynamic noise from multi-wind turbines is studied. An efficient hybrid method is developed to jointly predict the aerodynamic and aeroacoustics performances of wind turbines, such as blade loading, rotor power, rotor aerodynamic noise sources, and propagation of noise. This numerical method combined the simulations of wind turbine flow, noise source and its propagation which is solved for long propagation path and under complex flow environment. The results from computational fluid dynamics (CFD) calculations not only provide wind turbine power and thrust information, but also provide detailed wake flow. The wake flow is computed with a 2D actuator disc (AD) method that is based on the axisymmetric flow assumption. The relative inflow velocity and angle of attack (AOA) of each blade element form input data to the noise source model. The noise source is also the initial condition for the wave equation that solves long distance noise propagation in frequency domain. Simulations were conducted under different atmospheric conditions which showed that wake flow is an important part that has to be included in wind turbine noise propagation.

scholarly journals Measurement of Mutual Interference Sound of Columnar Objects in Air Flow

2018 ◽  
Vol 151 ◽  
pp. 03004
Author(s):  
Shohji Hamada ◽  
Yoshifumi Yokoi
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Flow Visualization ◽  
Mutual Interference ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Flow State ◽  
Visualization Experiment ◽  
Experimental Apparatus ◽  
Karman Vortex

When a columnar object is put in a flow, Karman vortex is formed, and aerodynamic noise is generated. It is known that when multiple columnar objects are put in a flow, the flow state becomes complex. This can be known by flow visualization experiment. On other hands, there are few researches on flow sound in the case of mutual interference, that it is not as far as the authors know. Measurement of flow sound is performed using a microphone. Therefore, it is necessary to confirm the sound of the interference flow field reaches the microphone outside the flow field without changing. In this research, experiments were measured to confirm flow sound transmits to a microphone placed outside the flow field without changing. Based on the results, the aerodynamic noise measurement from the columnar object was performed using a low noise wind tunnel experimental apparatus. As a result, it was obtained that some findings on the sound of flow in mutual interference flow field

Numerical investigation on the contribution of underbody flow-induced noise on vehicle interior noise

2021 ◽  
pp. 095440702110044
Author(s):  
Yiping Wang ◽  
Mintao Du ◽  
Chuqi Su ◽  
Wenguang Wu
Keyword(s):  
Noise Source ◽  
Interior Noise ◽  
Experimental Result ◽  
Aerodynamic Noise ◽  
Acoustic Response ◽  
Vehicle Model ◽  
Vehicle Interior ◽  
Wind Noise ◽  
Flow Induced Noise ◽  
Computational Fluid Dynamics Cfd

Aerodynamic noise transmitted through greenhouse panels and sealing often dominates the higher frequencies of the interior noise level, whereas the underbody area contributes mainly to low and middle frequencies. A method that unsteady Computational Fluid Dynamics (CFD) for exterior airflow combined with Finite Element Method (FEM) for interior acoustic response was used. To validate the accuracy of this method, the interior wind noise of a simplified vehicle model proposed by Hyundai was computed. The comparison between the computational and experimental result showed that this method had enough accuracy to compute the interior wind noise induced by the exterior flow field. Then, the same method was used to compute the wind noise transmitted through the underbody of a passenger car. The characteristic of the noise source and noise inside the cabin was revealed, and the contribution of underbody flow-induced noise to the interior noise was also investigated. Finally, the influence of the underbody panels thicknesses on the interior wind noise was evaluated.

Sign in / Sign up

Export Citation Format

Share Document