| Project/Area Number |
11650519
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
HASEGAWA Kazuyoshi Hokkaido Univ., Grad.School of Eng., Instructor, 大学院・工学研究科, 助手 (70001328)
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| Co-Investigator(Kenkyū-buntansha) |
TATSUZAWA Hiromasa Water Resources Development Public Corporation, Research Institute, Hydraulic Div., Senior Research Engineer, 試験研究所, 主任研究員
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | mountain river / bedform / alternating bars / linear instability analysis / sand waves / alternating sorting waves / Talbot sediment size distribution / steep channel experiment with heterogeneous bed materials / 砂礫堆 / 分級波 / 急勾配水路実験 |
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| Research Abstract |
The aim of the research is to elucidate the properities of medium-scale bedforms evolving on mountain rivers from view points of the critical condition for generation and the functions to other bedforms and flows. Following results were obtained from steep channel experiments with heterogeneous materials and analyses within the research term :
1. It was found from the linear instability analysis for the system of sediment and flow, that there are two significant solutions for maximum growth rate of the perturbations of bed displacement, velocity etc. One corresponds to the growth of alternating bars and the other corresponds to sorting waves of bed gravel and sand.
2. A wavelength of an alternating bar growing on a steep channel bed with heterogeneous materials has a tendency to become 3 times longer than a wavelength of bar on an alluvial bed. The alternating bars concentrate the flow with sorting the gravel and sand on the bed to form step-pools.
3. Under the hydraulic condition of high shearing stress such the sorting instability dominates the bed elevation instability, a flat bed grows on the bed to form alternating fractions of large size pebbles with spacing in 1.5 times of a bar wavelength.
4. Sediment discharge to the two kind of bed form is not clearly different each other.
5. Very similar bedform to steps and pools in a natural stream evolved in the experimental channel when ribs superposed alternating bars. The bedform was seen applicable to a fish way as a new type.
6. In the experiment of high discharge, multiple rows bars rose on the bed. When a small discharge flow was run on this bed, braided channels occurred with medium-scale bars and ribs ; the morphological feature was very close to that of a natural mountain river.
7. Large-scale bed undulation caused by the multiple rows bars and change of the braided channels give a great influence to the discharge of sediment at the end of the experimental channel.
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