| Project/Area Number |
17560456
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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 |
水工水理学
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
TOMINAGA Akihiro Nagoya Institute of Technology, Graduate School of Engineering, Professor, 工学研究科, 教授 (60135530)
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| Co-Investigator(Kenkyū-buntansha) |
MASUDA Michiko Nagoya Institute of Technology, Graduate School of Engineering, Assistant Professor, 工学研究科, 助教授 (30304645)
SHO Kenjiro Nagoya Institute of Technology, Graduate School of Engineering, Assistant Professor, 工学研究科, 助教 (40283478)
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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: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | embayment / compound open channel / mid-level flood plain / vortex structure / sand deposition / suspended sediment / three-dimensional flow structure / PIV / 土砂体積 |
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| Research Abstract |
We investigated three-dimensional flow structures and sand deposition in an concavity zone in a compound open channel experimentally. We picked up the concavity shape, the relative level of concavity bed and the existence of spur dikes as design items and investigated their effects on the flow structures in concavity zones by using PIV method. Furthermore, sediment deposition tests was conducted in the same laboratory flume and the relation of flow structures to sediment transport process was considered.
The relative level of the concavity bed against the main channel bed was considered as a control parameter. A single vertical vortex is generated in a concavity zone in the case without overbank flow. In the case with overbank flow on flood plain, a transverse vortex coexists with the vertical vortex in the concavity zone. In rectangular concavity case, the longitudinal scale of the transverse vortex becomes larger relative to the vertical vortex with an increase of the depth of the con
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cavity. As a result, the flow pattern near the bed becomes very different from each other and this affects the amount and the shape of sand deposition. In trapezoidal concavity, skew step produces inclined transverse vortex. The longitudinal scale of this vortex becomes smaller than that in the rectangular case and this generates different flow patterns from the normal step case. Consequently, overbank flow causes transverse vortices in the concavity zone and then changes flow structures and sand deposition shape.
Next, we investigated flow structures and suspended sediment transport in concavity zone on triple section channel with flood plain, mid-level flood plain and main channel. In the triple section channel, transverse momentum exchange accelerates the velocity and then increases sediment transport rate on the flood plain. The sediment deposition rate in the concavity is much affected by the relative bed level. When the bed level of the concavity is the same as the main-channel bed, the bed load and the suspended load are transported from the main channel into the concavity. When the bed level of the concavity is higher than the main-channel bed, the flood-plain sediment load is transported from the concavity to the main channel. These features are well related to the 3-d flow structures in the concavity zones.
The vegetation in concavity zone prevents inflow from the main channel and changes reattachment length in down step zone. This effects makes sand deposition flatter than in the case without vegetation. Less
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