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特征流量级对窜沟形成和发展影响的数值研究

Preliminary study on effect of characteristic flow rates on formation and development of channelized ditches
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摘要 分汊河道心滩常常出现窜沟,使滩体活动性变强,影响河势稳定。窜沟的形成与发展主要是对不断变化的径流流量的综合响应,为了探究窜沟对于不同流量级径流响应的敏感程度,基于平面二维水沙耦合数值模型,研究不同流量级条件下初始为完整高大心滩的冲淤过程,数值再现了窜沟的形成和发展。研究表明,窜沟的形成与发展和特征流量紧密相关:(1)流量较小、水流不能漫滩时,水流走心滩左右两汊的主槽,窜沟无法生成;(2)中等流量、水流能漫滩,但滩面水深较小时,左右两槽水流交换在低洼的滩面发生,冲刷生成窜沟;(3)在大流量下,心滩基本没于水下,左右两槽水流交换减弱,没有窜沟生成。研究结果还显示,在不同的特征流量下,窜沟发生的位置会有摆动,且窜沟生成和发育的特征流量的量级在一定程度上取决于滩体的平面形态。在分汊河道心滩滩体稳定性研究方面,方法及结论具有参考价值。 Channelized ditches often occur on channel bars in a braided river,promoting the mobility of the bars and affecting the stability of river regime.Formation and development of these ditches is primarily a comprehensive response of the river to its volatile runoff.To explore the channeling sensitivity to river flow rates,a two-dimensional depth-integrated water-sediment-morphodynamic model is used in this work to study the erosion and deposition process of channel bars under different flow rates,and the formation and development of the ditches is reproduced numerically.Results show that the formation and development is closely related to the river’s characteristic flow rate.1)When the river flow rate is small and the water cannot flow over the bar,the flow runs through the left and right branches and no ditch will be generated;2)When the flow rate is in the medium range and the water just flows over the bar with a small depth on the bar,flow exchange between the two branches occurs through streams passing over the low-lying part of the bar bridge,and these streams will scour the bar and create channelized ditches;3)When the flow rate is large and a major part of the channel bar is underwater,the flow exchange is weakened and no ditch can be generated.This study also shows that at different characteristic flow rates of the river,the location of ditch formation will swing.And the threshold of the characteristic flow rates for the ditch to form and develop depends,to some extent,on the planar shape of the channel bar.The results of this work would be useful for the study of the stability of channel bars in branched rivers.
作者 雷云龙 胡鹏 曹志先 刘怀汉 李薇 LEI Yunlong;HU Peng;CAO Zhixian;LIU Huaihan;LI Wei(Ocean College,Zhejiang University,Zhoushan,Zhejiang 316021;State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430000;Changjiang Waterway Institute of Planning and Design,Wuhan 430000)
出处 《水力发电学报》 CSCD 北大核心 2019年第4期43-52,共10页 Journal of Hydroelectric Engineering
基金 长江航道局重点科研项目(K16-529112-016).
关键词 分汊河道 稳定性 江心洲 窜沟 特征流量 平面二维水沙耦合数值模型 数值研究 braided channel stability channel bar channelized ditch characteristic flow rate hydrosediment-morphodynamic model numerical study
作者简介 雷云龙(1993—),男,硕士生,E-mail:leiyunlong9@163.com;通信作者:胡鹏(1985—),男,副教授,E-mail:pengphu@zju.edu.cn.
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