| Project/Area Number |
59550338
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
ISHIKAWA Tadaharu Associate Professor, Faculty of Engineering, 工学部, 助教授 (50159696)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Masahiro Researcher, Faculty of Engineering, 工学部, 助手 (90171800)
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| Project Period (FY) |
1984 – 1985
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| Project Status |
Completed (Fiscal Year 1985)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1985: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1984: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Composite Channel / Lateral Mixing / Roughness Factor / 潅木 / 2次流 |
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| Research Abstract |
The roughness factor of a composite channel increses when there is a strong lateral mixing between the low water channel and the flood plain. Therefore, We carried out an experiment on the lateral momentum mixing in a shallow open channel where the primary shear is in vertical. The following three types of flow were examined. (1) A couple of flows parallel to each other with a velocity difference. (2) A wake behind a piar. (3) A boundary layer on the side bank. Results showed that the lateral mixing in a shallow open channel is similar to the mixing of free turbulent flow and that the lateral eddy viscosity is proportional to the product of a lateral velocity difference and a lateral shear layer thickness. A shallow water equation accompanied by the above expression of the eddy viscosity led to a method of estimating the roughness factor of a composite channel.
The flow resistance of bushes which often glow between the low water channel and the flood plain was studied by a field observation and a flume experiment. It is noteworthy that the coupling of the motion of bushes and the lateral seiche makes an regular emition of voltexes and enlarges the resistance.
A numerical calculation method was developed to estimate a secondary circulation intensity which influences a large effect on the stability of the low water channel bank. Experiments verified that this method is useful especially in a natural river channel which is often bending in ancomprecated manner.
The above results are served for the planning and designing a composite channel.
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