1991 Fiscal Year Final Research Report Summary
Investigations of 3-Dimensional flows in Non-uniform river Channels
| Project/Area Number |
02650351
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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 | Hokkaido University |
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Principal Investigator |
ITAKURA Tadaoki Hokkaido University, Fac. of Eng., Professor, 工学部, 教授 (70001138)
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| Co-Investigator(Kenkyū-buntansha) |
MORI Akio Hokkaido University, Fac. of Eng., Res. Associate, 工学部, 助手 (00001339)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Rapidly varied flow / Compound cross section / Secondary flow / Numerical calculation / River morphology / Flood flow / Groynes |
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| Research Abstract |
(1)Investigations of rapidly varied flows : Detailed measurements of flows were performed in rectangular flumes to investigate secondary flows and 3-dimensional structures in the rapidly varied flows. Thin flat plates were fixed at the side walls of the flumes at right angle which simulate groyne or array of groynes which caused the rapidly varied flows. The investigations were perfomed in two flumes which have fixed bed and movable bed of sand, respectively. In the fixed bed flume, two vortices are formed upstream of the groyne which have horizontal axes.
However, on the movable bed, the flow at the upstream face of the groyne is only down-ward and the secondary flows go out from both upstream and downstream sides of the groyne to the central part of the channel. These secondary flows are very well reproduced by a new numerical simulation model. (2)Flows in compound cross section at river bend : A new numerical simulation model was developed to investigate the flood flows in compound cross sections at river bends. An interaction between the meandering flow in the main channel and the flow on the flood plain was investigated in the model adopting the Voronoi diagram and the finite-volume method. A remarkable feature was found at the positions where the flow on the flood plain merges into the meandering main flow.
A herical flow which has an unusual inverse rotation is developed and the resistance to flow increases by the influence of the merging momentum. The the deepest position of scour sifts to the central part of the main channel. On the other hand, the outside bank is exposed to erosion, where the flow in the main channel goes up to the flood plain. These calculated results compare well with the observations of flood flow in the Rumoi River, supporting the validity of the simulation model.
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