江心洲头部冲淤动力临界特性  

Critical features of flow dynamics at the entrance of multi-branched channels

作　　者：韩剑桥[1] 孙昭华[1] 冯秋芬[1] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,湖北武汉430072

出　　处：《水科学进展》2013年第6期842-848,共7页Advances in Water Science

基　　金："十二五"国家科技支撑计划资助课题(2012BAB04B04);中央高校基本科研业务费专项资金资助项目(2012206020212)~~

摘　　要：不同流量级下,分汊河段进口主流摆动导致江心洲头部的平面冲淤分布呈现出复杂变化特征。为探究江心洲头部冲淤与来流过程之间的响应关系,借助长江中下游多个分汊河段内水沙、地形资料,对江心洲头部水动力特征实施了数值模拟,并对不同流量级下的河床变形强度进行综合比较。研究表明:江心洲头部低滩的冲淤动力随着流量涨落呈现出明显的临界特性,冲淤过程中存在大、小两个临界流量Q1与Q2,在介于两个临界流量之间的流量级持续作用下,洲头低滩发生冲刷;流量大于Q1或小于Q2时,洲头低滩表现为淤积。由于不同流量级造成的冲淤效果不同,因而水文过程中各级流量的持续时间,是影响洲头低滩年内、年际变形的主要因素。At the entrance reach of multi-branched channels, the temporal and spatial distribution of sediment erosion or deposition often changes due to the position of main stream shifting with different income discharge. In order to in- vestigate the relation between the magnitude of bed deformation and flow discharge, numerical simulations of flow fields are carried out and channel morphology comparisons were made across different discharge in several braided reaches of the middle Yangtze. It is found that flow dynamics exhibits a critical character when incoming discharge changes. That indicates the existence of two critical discharges Q1 and Q2. The head of sandbar will be eroded when the incoming discharge ranging between Q1 and Q2. The head of sandbar will be deposited when the incoming discharge is above Qt or below Q2. Because the impacts of incoming discharge on river bed deformation are different according to different discharge magnitudes, the seasonal or annual adjustment of bed morphology at the head of sandbars will mainly depend on the duration of discharge process.

关 键 词：分汊河道 江心洲 冲淤动力 临界特性 

分 类 号：TV147[水利工程—水力学及河流动力学]