Experimental study on effect of turbulent structure on small falling air-borne particle.
| Project/Area Number |
17560144
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
USHIJIMA Tatsuo Nagoya Institute of Technology, Graduate School of Engineering, Research Associate, 工学研究科, 助手 (50314076)
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| Co-Investigator(Kenkyū-buntansha) |
KITOH Osami Nagoya Institute of Technology, Graduate School of Engineering, Professor, 工学研究科, 教授 (10093022)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Turbulence / Multiphase Flow / Terminal velocity / Stokes number / 乱入 / 流体力学 |
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| Research Abstract |
Velocity of falling particle through homogenous and isotropic turbulence was measured to study the effect of turbulence on motion of small particle, which has little influence on turbulence.
Isotropic and homogeneous turbulence was generated in box-turbulence generator that had been developed in our laboratory. Four counter-rotating grids are installed in a rectangular box. By rapid rotation, isotropic and homogeneous turbulence with zero-mean flow was realized between grids. Particles are dropped in a turbulent velocity field and were recorded by high-speed camera and the image was analyzed by Particle Tracking Velocimetry (PTV) to estimate the velocity of the falling particles.
Varying the intensity of turbulence, we measured the mean velocity of falling particles, which are compared with the terminal velocity of particle, and investigate the effect of the turbulence. Two types of particle (PMMA and solid glass) are used in the study. The size of particle is 100 μm and much smaller than the Kolmogorov scale or the smallest scale of the turbulence. It is, therefore, assumed that the flow around particle is uniform. By varying the intensity of the turbulence, the aerodynamic response time of particle to the turbulent time scale are controlled and the increase/decrease in the mean velocity of falling velocity are examined. The past research reported the maximum increase of the falling velocity for the time ratio of order unity. However, the reversed trend is observed for the solid glass particles (2% decrease at maximum) while the same trend (15% increase at maximum) for the PMMA particles.
It is found that the time scale ratio is not the unique factor to determine the effect of turbulence on particle motion. Therefore, modelling of the effect of turbulence on particle motion from the past DNS research needs some caution. We shall continue the current research, seeking for another factor to control the particle motion in a turbulent flow.
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Report
(3 results)
Research Products
(6 results)
