1997 Fiscal Year Final Research Report Summary
Coherent Structures and associated sediment transport in unsteady open-channel flows
| Project/Area Number |
08455230
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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 | 一般 |
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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 |
NEZU Iehisa KYOTO UNIVERSITY Dept.of Global Environment Eng., Professor, 工学研究科, 教授 (30109029)
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| Co-Investigator(Kenkyū-buntansha) |
ONITUKA Kouki KYOTO UNIVERSITY Dept.of Global Environment Eng., Research Associate, 工学研究科, 助手 (20293904)
TOMINAGA Akihiro Dept.of Civil Eng., Nagoya Institute of Tech., 工学部, 助教授 (60135530)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Unsteady flow / Open-channel flow / Coherent vortex / Separated vortex / Kolk-Boil vortex / Laser Doppoler anemometer / Space-time correlation / Conditional sampling technique |
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| Research Abstract |
There are some important topics in which the unsteadiness effects on turbulent structures should be considered. In open-channel flows such as rivers and estuaries, various coherent vortices are often observed and greatly affect sediment transport. These coherent structures often occur especially in flooded fluvial rivers. The hydrodynamic behavior of flood structures is quite different between the rising and falling stages of flood period. In the rising stage, the concentration of suspended sediment increases due to the kolk-boil vortex because the rising stage corresponds to thegrowing period of dunes and because separated vortex from the dune collides intermittently at the next dune and washes out bed materials around there.
In this study, unsteadiness and pressure gradient effects on the coherent structures in unsteady open-channel flows and steady flows over sine-wave and dune beds, were investigated so that the growing process of the dunes and the behavior of the suspended sediment can be explained dynamically. Especially, the specific 3-D behaviors of coherent vortices over dunes were accurately measured by means of simultaneous use of two sets of LDA.The differences of convection properties on coherent vortices were discussed by evaluating the conditional space-time correlation.
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