1996 Fiscal Year Final Research Report Summary
Study on stability of organized horizontal vortices and sediment transport in compound open channel flow
| Project/Area Number |
07455195
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Tokyo Institute of Technology |
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Principal Investigator |
IKEDA Syusuke Faculty of Eng., Tokyo Institute of Technology, Professor, 工学部, 教授 (60016590)
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| Co-Investigator(Kenkyū-buntansha) |
IZUMI Norihiro Faculty of Eng.Tohoku Univ.Associate professor, 工学部, 助教授 (10260530)
YAGI Hiroshi Faculty of Eng., Tokyo Institute of Technology, Associate professor, 工学部, 助教授 (80201820)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Compound open channel flow / Horizontal organized vortices / Vortex streets / Shear instability / Reynolds stress |
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| Research Abstract |
It has been known that shear instability generates large horizontal vortices at the junctions of main channel and flood plains in two-stage channel. A series of laboratory tests were performed by varying the main channel width, and the tests were conducted for 3 cases of water depth. Fluid velocity and water surface elevation were measured by using laser-Doppler velocimetry and capacity-type wave gage, respectively. It was found that two arrays of vortex streets become very stable at b/H=5, in which b is main channel width and H is main channel depth. The Reynolds stress at the junction shows a peak value at b/H=5 for all cases of water depth. The wavelength of vortices was predicted successfully in terms of linear instability analysis.
A series of laboratory tests were also performed in open channel flows with bank vegetation, in which the flow fields become more 2-dimensional than compound open channel flow. Similarly in compound open channel flow, when the vortex streets becomes stable staggered array, the Reynolds stress takes a peak value. The peak value of Reynolds stress is larger than that of compound open channel flow. A numerical computation employing SDS and 2DH turbulence model originally proposed by Nadaoka and Yagi was performed to calculate the 2-dimanesional flow field, supporting the measurements.
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