1998 Fiscal Year Final Research Report Summary
Research on Noise Reduction of Air-conditioner based on the Acoustic Analysis using Large Eddy Simulation
| Project/Area Number |
09555065
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Fluid engineering
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| Research Institution | Osaka University |
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Principal Investigator |
MIYAKE Yutaka Faculty of Engineering, Osaka University Professor, 大学院・工学研究科, 教授 (50029005)
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| Co-Investigator(Kenkyū-buntansha) |
URSULA BUECK 山洋電機(株), メカトロニクス研究所, 主任研究員
KUROKAWA Michihiro Sanyo Electric Co., Ltd.Chief Researcher, メカトロニクス研究所, 主任研究員
OHTA Takashi Faculty of Engineering, Research Assistant, 大学院・工学研究科, 助手 (10273583)
TSUJIMOTO Kouichi Faculty of Engineering, Research Associate, 大学院・工学研究科, 助手 (10243180)
KAJISHIMA Takeo Faculty of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (30185772)
BUECKLE Ursula Sanyo Electric Co., Ltd.Chief Researcher
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| Project Period (FY) |
1997 – 1998
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| Keywords | Turbulent Flow / Large-Eddy Simulation / Direct Numerical Simulation / Aeroacoustics / Air conditioner / Subgrid Scale Model / Computational Fluid Dynamics |
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| Research Abstract |
In order to simulate the complicated turbulence flow field concerning to the air-conditioner equipment, we developed a high-order finite difference scheme using the generalized coordinate system. By applying it to a direct simulation of turbulent flow in a wavy channel, we confirmed our scheme showed enough accuracy for our purpose. Furthermore using this DNS databases, a generalized normal stress model (GNS model) was found to be able to predict the flow separation on the wavy wall.
To investigate the mechanism of generation of aerodynamic noise and to find an algorithm to reduce the broad band noise emitted from turbulent eddies ; we formulated suitable indices of sound source. In this study, acoustic fields from 2D Cavity flow and rotating vortex pair are reproduced with the direct method proposed by Hardin and Pope. As a result, the sources of propagated sound to the far field is identified by the second time derivative of pressure fluctuation. Based on this index, we examined the acoustic field emitted from wall turbulence. We revealed that the coherent structure of streamwise vortices and hair-pin-like vortices are responsible for turbulent noise. Also some coherent bubble-like structures of acoustic pressure were observed further away from the wall, while the frequency spectra of acoustic field is characterized to be broadband and disorder. Moreover, a numerical experiment to reduce the intensity and source of noise was examined by the control of the vortex structures in near-wall region. As a result, the attenuation of near-wall structure caused the reduction of sound pressure level in far field. Thus we confirmed that the turbulence control technique was also effective for noise reduction.
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