1994 Fiscal Year Final Research Report Summary
Turbulent Structures and the associated sucliment transport
| Project/Area Number |
05555144
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
水工水理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAGAWA Hiroji Kyoto University, Civil Eng., Professor, 工学部, 教授 (60027216)
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| Co-Investigator(Kenkyū-buntansha) |
KITAMURA Tadaaki Kyoto University, Civil Eng., Reser.Assistant, 工学部, 助手 (00243064)
GOTO Hitoshi Kyoto University, Civil Eng., Reser.Assistant, 工学部, 助手 (40243068)
MURAKAMI Shogo Kyoto University, Civil Eng., Reser.Assistant, 工学部, 助手 (70166247)
TOMINAGA Akihiro Nagaya Inst.Tech., Civil Eng., Assoc.Professor, 工学部, 助教授 (60135530)
NEZU Iehisa Kyoto University, Civil Eng., Assoc.Professor, 工学部, 助教授 (30109029)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Turbulence / Unsteady Flow / Open Channels / Laser Doppler anemometer / Particle-Tracking Velocimetry / Compound Open Channel Flows / PTV / FLDA |
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| Research Abstract |
Turbulence measurements over smooth wall in unsteady open-channel flows were conducted accurately by the simultaneous use of two-component LDA system and waterwave gauges. The "general" log-law distributions in which the von Karman constant is universal one of k=0.41 but the integration constant A is a function of main-flow conditions, were satisfied well in the wall region for both the rising and falling stages of flood. On the other hand, the log-wake law was reasonably applied to the outer region including the depth-varying zone. The Coles'wake parameter PI increased for the rising stage, whereas it decreased for the falling one. The turbulence is stronger for the rising stage than for the falling one, except for very near the free surface. These unsteady characteristics in open-channel flows with varying the water surface are quite different from those in closed duct flows. Of particular significance is the findings of counterclockwise loop of the velocity and turbulence against the varying depth in unsteady open-channel flows.
Next, in the further study, images of very small 100 mum diameter particles uniformly suspended in compound open-channel flows were recorded on an optic disc using a high-sensitive CCD camera and 2W Argon-ion laser slit illumination techniques. Instantaneous velocities at each point in the laser slit plane were measured from these continuous four images of one particle. This new technique called the "Particle-Tracking Velocimetry (PTV)" seems to be very powerful to investigate space-time correlation structures of coherent vortices of turbulence using the conditional sampling method of quadrant motions of velocity components because simultaneous velocity components can be obtained at all grid points of arbitrary section plane of water flows.
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