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

scholarly journals On the Study of Aerodynamic Noise Measurement of Turbulent Flow Field with a Low-noise Turbulence Generator

2007 ◽  
Vol 73 (732) ◽  
pp. 1629-1636 ◽  
Author(s):  
Akiyoshi IIDA ◽  
Kenji MORITA ◽  
Hiroyuki TANIDA ◽  
Toshitaka MINBU ◽  
Akisato MIZUNO ◽  
...  
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Low Noise ◽  
Noise Measurement ◽  
Aerodynamic Noise ◽  
Turbulent Flow Field ◽  
Turbulence Generator

scholarly journals Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

2014 ◽  
Vol 6 ◽  
pp. 712421 ◽  
Author(s):  
Shuiqing Zhou ◽  
Jun Wang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Hybrid Technique ◽  
Field Calculation ◽  
Pressure Amplitude ◽  
Centrifugal Fan ◽  
Hybrid Techniques

An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

Visualization Experiment with PIV and Analysis of Flow Field in Hydrodynamic Coupling

2010 ◽  
Vol 29-32 ◽  
pp. 1327-1333
Author(s):  
Xiu Quan Lu ◽  
Wen Xing Ma ◽  
Li Dan Fan ◽  
Bo Sen Cai
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Internal Flow ◽  
Two Dimensions ◽  
Flow State ◽  
Complex Flow ◽  
Piv Technique ◽  
Hydrodynamic Coupling ◽  
Visualization Experiment ◽  
Testing Technology

In order to study the complex flow state of the internal flow field while the hydrodynamic coupling is under working conditions, the two dimensions PIV technique of the modern testing technology is adopted to test and analyze typical working conditions of hydrodynamic coupling. According to the experimental results, the internal flow field of the typical working conditions is analyzed and compared in qualitative way. The research of this paper has guiding significance for the hydrodynamic coupling design.

Prediction of Aerodynamic Noise Radiated From a Vertical-Axis Wind Turbine

2003 ◽  
Author(s):  
Akiyoshi Iida ◽  
Akisato Mizuno ◽  
Kyoji Kamemoto
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Sound Source ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Unsteady flow field and flow induced noise of vertical axis wind turbine are numerically investigated. The flow field is numerically calculated by the vortex method with core-spreading model. This simulation obtains aerodynamic performance and aerodynamic forces. Aerodynamic noise is also simulated by using Ffowcs Williams-Hawkings equation with compact body and low-Mach number assumptions. Tip speed of rotor blades are not so high, then the contribution of the moving sound source is smaller than that of the dipole sound source. Since the maximum power coefficient of VAWT can be obtained at lower tip-speed ratio compared to the conventional, horizontal axis wind turbines, the aerodynamic noise from vertical axis wind turbine is smaller than that of the conventional wind turbines at the same aerodynamic performance. This result indicates that the vertical axis wind turbines are useful to develop low-noise wind turbines.

Effects of Periodic Holes on the Suppression of Aeroacoustic Noise From a Pantograph Horn

2003 ◽  
Author(s):  
Takehisa Takaishi ◽  
Mitsuru Ikeda ◽  
Chisachi Kato
Keyword(s):  
Wind Tunnel ◽  
Acoustic Resonance ◽  
Flow Fields ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Spanwise Direction ◽  
Large Structure ◽  
Unstable Flow ◽  
Aeroacoustic Noise ◽  
Flow Through

Three types of pantograph horn model; simple cylinder, a cylinder with periodic holes and a cylinder with a continuous slit, are tested in a low noise wind tunnel to compare their characteristics of aerodynamic noise and flow fields in the wake. Formation of strong vortices of alternate sign that have large structure in the spanwise direction is suppressed due to the flow through holes or the slit. The cylinder with the continuos slit is proved to reduce the noise sufficiently, but an unstable flow through the slit seems to produce distinct noise. Since formation of strong vortices is mainly suppressed due to momentum injection through holes or the slit, periodic holes have little effect on collapsing the spanwise structure of vortices, but they contribute to making the flow around the horn stable. The shape of holes should be optimized to avoid strong acoustic resonance.

Numerical Analysis of Flow Field and Aerodynamic Noise in Wind Tunnel

2016 ◽  
Vol 2016 (0) ◽  
pp. 1206
Author(s):  
Byungjin AN ◽  
Hiroyuki OGOSE ◽  
Motohiko NOHMI ◽  
Hideaki FUEKI
Keyword(s):  
Numerical Analysis ◽  
Wind Tunnel ◽  
Flow Field ◽  
Aerodynamic Noise

scholarly journals Characteristics and Mechanism Analysis of Aerodynamic Noise Sources for High-Speed Train in Tunnel

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Xiao-Ming Tan ◽  
Hui-fang Liu ◽  
Zhi-Gang Yang ◽  
Jie Zhang ◽  
Zhong-gang Wang ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Sound Source ◽  
High Speed ◽  
Spectral Characteristics ◽  
Oscillation Mode ◽  
Scale Model ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Noise Sources

We aim to study the characteristics and mechanism of the aerodynamic noise sources for a high-speed train in a tunnel at the speeds of 50 m/s, 70 m/s, 83 m/s, and 97 m/s by means of the numerical wind tunnel model and the nonreflective boundary condition. First, the large eddy simulation model was used to simulate the fluctuating flow field around a 1/8 scale model of a high-speed train that consists of three connected vehicles with bogies in the tunnel. Next, the spectral characteristics of the aerodynamic noise source for the high-speed train were obtained by performing a Fourier transform on the fluctuating pressure. Finally, the mechanism of the aerodynamic noise was studied using the sound theory of cavity flow and the flow field structure. The results show that the spectrum pattern of the sound source energy presented broadband and multipeak characteristics for the high-speed train. The dominant distribution frequency range is from 100 Hz to 4 kHz for the high-speed train, accounting for approximately 95.1% of the total sound source energy. The peak frequencies are 400 Hz and 800 Hz. The sound source energy at 400 Hz and 800 Hz is primarily from the bogie cavities. The spectrum pattern of the sound source energy has frequency similarity for the bottom structure of the streamlined part of the head vehicle. The induced mode of the sound source energy is probably the dynamic oscillation mode of the cavity and the resonant oscillation mode of the cavity for the under-car structure at 400 Hz and 800 Hz, respectively. The numerical computation model was checked by the wind tunnel test results.

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