| Project/Area Number |
02452296
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
自然地理学
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| Research Institution | University of Tsukuba |
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Principal Investigator |
MATSUMOTO Eiji (1991-1992) Univ. of Tsukuba, Inst. of Geoscience, Assoc, Prof., 地球科学系, 助教授 (10015571)
池田 宏 (1990) 筑波大学, 地球科学系, 助教授 (20015986)
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| Co-Investigator(Kenkyū-buntansha) |
ISEYA Fujiko Jobu Univ., Dept. of Commercial Sci Assoc. Prof., 商学部, 助教授 (00193384)
IKEDA Hiroshi Univ. of Tsukuba, Inst. of Geoscience, Assoc. Prof., 地球科学系, 助教授 (20015986)
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| Project Period (FY) |
1990 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1992: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1991: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1990: ¥4,100,000 (Direct Cost: ¥4,100,000)
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| Keywords | Sediment transport / Heterogeneous sediment / Closed duct / Dunes / Sedimentary structure / Rivers / Flume experiments / 粒径による分級現象 |
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| Research Abstract |
We have conducted an experimental study of the nature of bed features in unidirectionary flows as a function of flow strength and sediment sorting by formulating several sediment mixtures with the same mean size of about 4 mm but with wide varying sorting and making series of run at several mean flow velocities over each sediment mixture. In order to conduct this US-Japan cooperative project, a new recirculating flow duct was built at the Environmental Research Center (ERC) in Tsukuba. When the bed shear stress is larger than twice the critical shear stress of the largest grains on the bed, dunes develop on a gravel bed in the closed duct. As the migration rate of dunes are twice the mean travel velocities of sediment, bedload transport rate may be evaluated by the migration rate of dunes. When the bed shear stress is smaller than the critical shear stress of the coarse population among bed material, the fine fraction moves as thin patches or small starved dunes over an immobile coarse substrate. There is a continuous transition between sheets and dunes over a range of botu discharge and proportion of fine grains.
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