| Project/Area Number |
16360242
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
水工水理学
|
|---|
| Research Institution | HOKKAIDO UNIVERSITY |
|---|
Principal Investigator |
SHIMIZU Yasuyuki Hokkaido University, Graduate school of engineering, Professor, 大学院工学研究科, 教授 (20261331)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
IZUMI Norihiro Hokkaido University, Graduate school of engineering, Professor, 大学院工学研究科, 教授 (10260530)
WATANABE Yasunori Hokkaido University, Graduate school of engineering, Associate Professor, 大学院工学研究科, 助教授 (20292055)
WATANABE Yasuharu Civil Engineering Research Institute For Cold Region, Chief Researcher, 上席研究員 (00344424)
TAKEBAYASHI Hiroshi Tokushima University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (70325249)
|
|---|
| Project Period (FY) |
2004 – 2006
|
| Project Status |
Completed (Fiscal Year 2006)
|
| Budget Amount *help |
¥14,700,000 (Direct Cost: ¥14,700,000)
Fiscal Year 2006: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2005: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2004: ¥10,400,000 (Direct Cost: ¥10,400,000)
|
|---|
| Keywords | weakly nonlinear stability analysis / stream / double-row bar / dune / non-uniform sediment bed / 網状化 / 画像計測 / 数値計算モデル / 谷低平地 / 中規河床波 / 弱非線形解析 / デューン / 復列砂州 / 乱流 / 浮遊砂 / 平衡状態砂洲波高 / 植生 / 小規模河床波 / 非線形解析 / 圧力勾配 / リップル / 乱流モデル |
|---|
| Research Abstract |
A weakly nonlinear analysis considering the interference between alternate bar and double-row bar has been developed. Findings show that when the two modes are on the same order, the mode cross interference controls development process of each wave and they cannot grow simultaneously. The development process of bars is strongly influenced of the mode cross interference. Hydraulic experiments and the weakly nonlinear analysis, by setting several hydraulic conditions under which either alternate bars or double-row bars formed, have been conducted to clarify a changing process of bar shape formed during flood at usual time. It is found that the channel shape at usual time is strongly affected by the bar shape during flood.
Effect of unsteady characteristics of flow and vegetation growth on number of braided streams and temporal stability of streams has been studied. The results show that the number of streams decreases and temporal change of streams is suppressed with vegetation under unsteady flow conditions. Furthermore, dynamic characteristics of bars on bed with non-uniform sediment have been studied. The results show that bar geometry on bed with non-uniform sediment has been changed with time and does not approach equilibrium state.
A new model was proposed taking proper account of the functional relation between the Froude number and the Shields number by revisiting the existing weakly nonlinear stability analysis of the transition of dune and flat bed regimes. It is found that, from the analysis, the dune-flat bed transition is characterized by subcritical bifurcation in the range of relatively small average bed slopes, and large velocity coefficient. In addition, Izumi extended the existing model of the inception of channels to the more general cases in which the base state slope profile is arbitrary given. The analysis shows that the spacing of channels is approximately one thousand times the depth of surface flow on slopes.
|
