Mechanism of Sudden Channel Change of Mountainous Rivers due to Hydraulic Jump in Channel Bifurcations.

河道分叉处水跃引起的山地河流河道突变机理。

• 批准号: 04650447
• 负责人: HASEGAWA Kazuyoshi
• 金额: $ 1.28万
• 依托单位: Hokkaido University, Faculty of Engineering
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650447/
• 关键词: Mountainous River; Bifurcated Channel; Supercritical Flow; Hydraulic Jump; Channel Blocking; Sediment Deposition; Momentum Equation; Divided Discharge Ratio; 河道閉塞; 流砂量配分比; 流速分布; 水面形; MaCormack法; 高解像スキーム計算

The purpose of this study is to make clear the origin of channel blocking phenomena sometimes observed in a bifurcated channel in mountain rivers. The followings were found through field observations, model experiments and theoretical analysis for origin of channel blocking :1.Three kinds of bifurcation patterns of channels are found in mountain rivers : Those are inner, outer and straight branching. Large scale of blocking takes place in outer branching channel.2.A large amount of sediment deposition to block the entrance of one bifurcated channel are brought on by a hydraulic jump which takes place in the front of bifurcation wall (i.e. island). This was verified through the experiments.3.The momentum equations for the flowing direction and for the normal direction to it, applied to two control volume sections enclosing the bifurcation of channel, have four kinds of solutions with respect to the divided discharge ratio and water depths at the two entrances of bifurcated channel : They are corresponding to any state that two channels are in supercritical flow, or one is in supercritical and the other is in ordinal flow, or both are in ordinal flow.4.It was confirmed in the experimental channel that the divided discharge ratio shifts from one solution to others when total discharge was reduced in steps ; the channel blocking was advanced with the change of discharge.5.From the above, it will be concluded that origin of a blocking of bifurcated channel is a large amount of sediment deposition in a hydraulic jump which takes place near the bifurcation of channel and the sudden discharge change due to the shift of flowing state.

本研究旨在探讨山区河流分汊河道阻塞现象的成因。通过野外观测、模型试验和理论分析，对山区河流阻塞成因进行了研究：1.山区河流的河道分汊方式有内分汊、外分汊和直分汊3种。外汊道发生大面积阻塞; 2.汊道分汊壁（即岛）前发生水跃，造成大量泥沙淤积阻塞一汊道进口。3.应用于两个控制体积段的水流方向和水流法向动量方程，对于分流比和两个分叉口的水深，有四种解：它们对应于两个通道处于超临界流动或一个通道处于超临界流动而另一个通道处于有序流动的任何状态，4.在实验通道中证实了当总流量逐步减小时，分流比从一种溶液向另一种溶液转移;随着流量的变化，通道阻塞提前。5.由上可知，得出了分汊河道堵塞的原因是分汊附近水跃的大量泥沙淤积和分汊时流量的突变，流动状态的转变。

项目成果

K.Hasegawa,T.Mizugaki: "Analysis of Blocking Phenomena in Bifurcated Channels Found in Mountainous Rivers" Proceedings of ASCE National Conference on Hydraulic Engineering.1-5 (1994)

K.Hasekawa，T.Mizugaki：“山地河流中分岔河道阻塞现象的分析”ASCE全国水利工程会议论文集.1-5（1994）

K.Hasegawa: "Changes of Bifurcated Channe48l in Mountainous Rivers." Proc.of Workshop on Hydraulics and Hydrology in cold Regions.205-216 (1993)

K.Hasekawa：“山区河流分叉河道48l的变化”。

K.Hasegawa: "Flow and Sediment Deposition in a Steep Bifurcated Channel with Movable Bed" Proceedings of Hokkaido Branch of JSCE. Vol.50 (in Japanese). 504-507 (1994)

K.Hasekawa：“具有可移动床的陡峭分叉河道中的流动和沉积物”JSCE 北海道分会论文集。

長谷川和義: "移動床急勾配分岐流路における流れと河床の堆積" 土木学会北海道支部論文報告集. 50. 504-507 (1994)

Kazuyoshi Hasekawa：“移动床陡坡分支河道中的流动和床沉积”日本土木工程学会北海道分会论文报告 50. 504-507 (1994)。

長谷川 和義: "急勾配分岐水路における跳水の発生と土砂堆積" 土木学会北海道支部論文報告集. 48. 439-444 (1992)

Kazuyoshi Hasekawa：“陡坡支流河道中水跃和泥沙沉积的发生”日本土木工程学会北海道分会论文集 48. 439-444 (1992)。