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Unstability of meandering streams and river bed erosion by meandering streams

曲流的不稳定及曲流对河床的侵蚀

基本信息

批准号：
07650602
负责人：
FUJITA Masaharu
金额：
$ 1.28万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650602/
关键词：
meandering stream meander river bed erosion 2-dimensional bed variation river morphology numerical simulation 水みち侵食シミュレーション

项目摘要

An formation process of meandering streams on river beds with non-uniform sediment was investigated experimentally and a simulation method for this process was developed using a 2-dimensional bed variation model. The results of this research are mainly as follows :(1) A formation process of meandering streamsAt the sirst step of the formation process observed in an experiment, the largest gravel stops at the crest of the untidunes. The gravel makes it easy for the transported sediment to be deposited just upstream of the gravel. A sand bar is formed through such a process and consequently a meandering stream is formed. The longitudinal and lateral sorting of bed material makes the stream more stable, but it turn unstable if the fine sediment flows out of the bar.(2) Development of simulation modelA method for simulating the formation process is developed using a 2-dimensional bed variation model. The comparison between the experimental and calculated results on the bed variation have shown the validity of the method.(3) ApplicationThe simulation model was applied to the formation process of the meandering streams observed in an experiment. The number and wave length of meandering streams are simulated by this method, but not the changeability of meandering streams. The simulated stream was fixed because the flow structure and sediment transport mechanism near the side walls are not precisely introduced in the model.

通过试验研究了非均匀沙条件下弯曲河道的形成过程，并建立了二维河床变化模型，对弯曲河道的形成过程进行了模拟。（1）曲流河的形成过程在实验观测到的曲流河形成过程的第一步，最大的砾石止于沙丘的顶部。砾石使被搬运的沉积物易于在砾石上游沉积。在这样的过程中，形成了一个沙洲，从而形成了一条曲流河。河床物质的纵向和横向分选使河流稳定，但细颗粒泥沙流出拦门沙后，河流又变得不稳定。(2)模拟模型的建立采用二维床层变化模型，建立了模拟地层形成过程的方法。床面变化的实验结果与计算结果的对比表明了该方法的有效性。(3)应用模拟模型被应用于实验中观察到的弯曲河流的形成过程。该方法模拟了曲流河的数量和波长，但不能模拟曲流河的变化。由于模型中没有精确地反映侧壁附近的水流结构和泥沙输移机理，因此模拟的水流是固定的。