Basic Research on Equivalent Sand-Grain Roughness of the Sand Waves of Small-Scale Having Three-Dimensional Configuration
| Project/Area Number |
63550378
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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 | Chuo University |
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Principal Investigator |
HAYASHI Taizo Chuo Univ., Fac. Sci. & Eng., Prof., 理工学部, 助教授 (60054938)
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| Co-Investigator(Kenkyū-buntansha) |
IMAI Takashi Ditto , Tech. Instruc., 理工学部, 実験講師 (00055071)
OHASHI Masakazu Ditto , Asst. Prof., 理工学部, 専任講師 (90160598)
青野 利夫 中央大学, 理工学部, 技術員 (90167221)
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| Project Period (FY) |
1988 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1990: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Sand waves of small scale / Alluvial river bed configurations of small scale / Three-dimensional ripples / Three-dimensional dunes / Equivalent sand-grain roughness / Three-dimensional sand waves of small scale / 相当砂粒粗度 / うろこ状砂連 / 小規模河床波の三次元性 / 河床形状抵抗 / 三次元小規模河床波 |
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| Research Abstract |
(1) Conditions of occurrence of three-dimensional sand waves of small scale have been studied by means of stability analysis of river bed. Potential flow theory is applied.
The initial rate of growth in dimensionless from of three-dimensional and waves has been obtained as a function of kd with parameters 1/k, Fr and C. Here, k and 1 = wave numbers of three-dimensional sand waves in the undisturbed main flow and spanwise directions, respectively ; d = mean depth of flow : F_r= Froude number ; and C = inclination factor relative to dimensionless delay distance of sediment particle. The domain of hydraulic conditions in which three-dimensional sand waves occur more easily than two-dimensional sand waves has been examined in detail.
(2) About 7,500 reliable data from laboratory flume and field experiments published by previous investigators have been analyzed to obtain the values of equivalent sand-grain roughness of alluvial channel bed. A new diagram is proposed for estimating the equivalent roughness to be formed in alluvial channels.
The analysis made shows that for any energy slope of flow the equivalent roughness in the dimensionless form relative to mean particle size has a distinct maximum for tau_*' = 0.2 about in which tau_*' is dimensionless grain-roughness bed shear stress.
(3) In order to grasp quantitatively the time and spatial variation of channel bed configuration of small scale at their occurrence and development stages a new method of measurement has been devised combining instrumentation by the use of laser slit-sheet illumination and computer-aided image-processing technique.
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Report
(4 results)
Research Products
(17 results)
