scholarly journals Extraction of sound field information from high-speed movie of flowing dust

2012 ◽  
Vol 33 (5) ◽  
pp. 316-319
Author(s):  
Mariko Akutsu ◽  
Yasuhiro Oikawa ◽  
Yoshio Yamasaki
Keyword(s):  
High Speed ◽  
Sound Field ◽  
Field Information

PIV Measurements in Diffuser of the Radial Pump

2015 ◽  
Author(s):  
Sung Yong Jung ◽  
Young Uk Min ◽  
Kyung Lok Lee
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Internal Flows ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Acquisition Device ◽  
Field Information ◽  
Radial Pump

The performance characteristics of the radial pump commonly used as a multistage (8 or 10 stage) pump have been investigated experimentally. Due to the complex three-dimensional geometries, the hydraulic performance of multistage pumps is closely related to the internal flows in diffuser and return vanes. In order to investigate the flow characteristics in these regions by Particle Image Velocimetry (PIV) technique, a transparent pump is designed. A 532 nm continuous laser and a high-speed camera are used as a light source and an image acquisition device, respectively. The velocity field information in a diffuser of the radial pump is successfully obtained by two-dimensional PIV measurements at various operating conditions.

Investigation of Pantograph Effect on High-Speed Train Noise

2012 ◽  
Vol 233 ◽  
pp. 239-242
Author(s):  
Xiao Feng Zhang ◽  
You Gang Xiao ◽  
He Lian Deng ◽  
Jian Feng Huang
Keyword(s):  
High Speed ◽  
Microphone Array ◽  
Broad Band ◽  
Side Wall ◽  
Sound Field ◽  
Noise Spectrum ◽  
Low Noise ◽  
Sound Insulation ◽  
Vehicle Noise ◽  
Sealing Performance

Using microphone and removable planar microphone array, the exterior and interior vehicle noise near pantograph were investigated when the train ran at 250-350km/h, the noise spectrum characters of these areas were obtained. The results show that at the pantograph seat and in the vehicle below pantograph, the noise spectrum show a broad band distribution, and the noise energy is mainly concentrated within the range of 100Hz-2kHz. Interior vehicle noise below pantograph is a non-uniform reverberant sound field, the regions with larger sound pressure level (SPL) are distributed near the roof, the floor, the side wall below the luggage. For reducing interior vehicle noise below pantograph, such measures as using low noise pantograph, adding sound insulation pad, filling sound absorption materials and improving sealing performance should be taken, and these measures should be effective at 100Hz-2kHz.

Fragmentation of acoustically levitating droplets by laser-induced cavitation bubbles

2016 ◽  
Vol 805 ◽  
pp. 551-576 ◽  
Author(s):  
Silvestre Roberto Gonzalez Avila ◽  
Claus-Dieter Ohl
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Surface Tension ◽  
Cavitation Bubble ◽  
High Speed ◽  
Size Range ◽  
Sound Field ◽  
Negative Pressures ◽  
Impulsive Pressure ◽  
Small Bubbles

We report on an experimental study on the dynamics and fragmentation of water droplets levitated in a sound field exposed to a single laser-induced cavitation bubble. The nucleation of the cavitation bubble leads to a shock wave travelling inside the droplet and reflected from pressure release surfaces. Experiments and simulations study the location of the high negative pressures inside the droplet which result into secondary cavitation. Later, three distinct fragmentation scenarios are observed: rapid atomization, sheet formation and coarse fragmentation. Rapid atomization occurs when the expanding bubble, still at high pressure, ruptures the liquid film separating the bubble from the surrounding air and a shock wave is launched into the surrounding air. Sheet formation occurs due to the momentum transfer of the expanding bubble; for sufficiently small bubbles, the sheet retracts because of surface tension, while larger bubbles may cause the fragmentation of the sheet. Coarse fragmentation is observed after the first collapse of the bubble, where high-speed jets emanate from the surface of the droplet. They are the result of surface instability of the droplet combined with the impulsive pressure generated during collapse. A parameter plot for droplets in the size range between 0.17 and 1.5 mm and laser energies between 0.2 and 4.0 mJ allows the separation of these three regimes.

KTX Interior-Noise Reduction Performance Comparison Using Multichannel Active-Noise Control

2012 ◽  
Vol 152-154 ◽  
pp. 1891-1898
Author(s):  
Hyeon Seok Jang ◽  
Young Min Kim ◽  
Saehan Kim ◽  
Taeoh Lee ◽  
Kwon Soon Lee
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Noise Control ◽  
Active Noise Control ◽  
Sound Field ◽  
Performance Comparison ◽  
High Speed Rail ◽  
Active Noise ◽  
Tunnel Section ◽  
Fxlms Algorithm

In many countries, the use of the KTX high-speed rail has been generalized of late. Therefore, its customers who initially pursued only convenience and speed have begun pursuing quality services such as comfort and stability. Thus, the importance of reducing the noise in the high-speed rail is increasing. The active noise is best choice to reduce noise because of being able to actively reduce the ambient noise coming from the environmental-factor changes. But it’s too hard in a three-dimensional closed-space sound field such as the interior of a high-speed rail. In this study, we used multichannel(2x2) FXLMS algorithm for applying ANC system in KTX. In detail, after measuring the noise inside KTX during its runs in South Korea, multichannel active noise control was simulated to determine the extent to which it can reduce the noise inside KTX. Simulation was done using a multichannel FXLMS algorithm for reducing the actual noise inside KTX and the noise reduction in the open-space section of KTX was compared with that in the tunnel section, and the active-noise-control performances in the low-frequency (below 500 Hz) region were compared.

Field Monitoring Using Sensor-Nodes with a Web Server

2005 ◽  
Vol 17 (2) ◽  
pp. 164-172 ◽  
Author(s):  
Tokihiro Fukatsu ◽  
◽  
Masayuki Hirafuji
Keyword(s):  
Remote Monitoring ◽  
Wireless Lan ◽  
High Speed ◽  
Field Experiments ◽  
Web Server ◽  
Sensor Nodes ◽  
The Internet ◽  
Transmission Network ◽  
Monitoring Applications ◽  
Field Information

In order to realize field and environment monitoring over long periods, we propose remote monitoring that responds flexibly and dynamically to change. Field Servers are one of the small monitoring sensor-nodes having a Web server accessed via the Internet and using a wireless LAN to provide a high-speed transmission network differing from traditional sensor-nodes. Monitoring with Field Servers enables easy installation, monitoring field information, and remote operation in any field. By providing a Web server for all modules, we can treat them collectively via the Internet. To evaluate this monitoring, we managed numerous Field Servers in different countries using an agent program. Field experiments show the system is safe and effective for remote monitoring applications.

scholarly journals The sources of jet noise: experimental evidence

2008 ◽  
Vol 615 ◽  
pp. 253-292 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
K. VISWANATHAN ◽  
K. K. AHUJA ◽  
J. PANDA
Keyword(s):  
High Speed ◽  
Noise Source ◽  
Jet Noise ◽  
Polar Angle ◽  
Sound Field ◽  
Source Distribution ◽  
Far Field ◽  
Noise Sources ◽  
Directional Information ◽  
Jet Mixing

The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.

Measurement of the Sound Field Radiated from Submerged Structure by Continuous Scanning

2013 ◽  
Vol 811 ◽  
pp. 337-340
Author(s):  
Chao Zhang ◽  
De Jiang Shang ◽  
Qi Li
Keyword(s):  
Measurement Method ◽  
Measurement Accuracy ◽  
Sound Field ◽  
Power Measurement ◽  
Discrete Point ◽  
Point Measurement ◽  
Continuous Scanning ◽  
Good Measurement ◽  
Measurement Experiment ◽  
Field Information

Distinguished from the conventional discrete-point measurement, a continuous scanning measurement method of the sound field radiated from submerged structure is proposed. By rotating the structure uniformly and continuously, the pressure signals were recorded by the hydrophones array that was located in the far field. The signals were analyzed by Fourier transform respectively, and the sound field information could be obtained by the further derivation. By using the continuous scanning measurement, the spectrum broadening phenomenon was observed and analyzed. And then the point sound source field simulation and the sound power measurement experiment were carried out to prove the reliability of this method. The results show that, compared with the conventional discrete-point measurement, the continuous scanning measurement can acquire more information in less measurement time, and reduce the measurement work greatly under good measurement accuracy.

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