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阻隔性河段能够阻隔上游河势调整向下游的传递,对稳定河势起到关键性作用。本文以长江中下游34个单一河段为研究对象,在系统总结长江中下游河道演变规律的基础上,归纳出阻隔性河段控制要素包括:单一微弯的河道平面形态、河段中上部无挑流节点;河相系数小于4;河道纵比降大于1.2?;凹岸黏粒含量高于9.5%;床沙中值粒径大于0.158 mm等。从Navier-Stokes方程出发,推导出河湾水流动力轴线弯曲半径的表达式,进而分析了各控制要素对水流动力轴线摆动及阻隔性河段形成的作用。阻隔性河段的判别条件为:不同流量级下水流动力轴线摆动力与河道边界条件约束力的比值始终小于1;阻隔性河段作用机理在于:即便上游河势发生调整,本河段的河道边界始终能约束主流摆动幅度,归顺上游不同河势条件下的主流平面位置,为下游河道提供了相对稳定的入流条件,从而阻隔上游河势调整向下游传递。
Barrier section can block the upstream river regulation to the downstream transmission, the stability of the river plays a key role. Based on the systematic analysis of the evolution of the river course in the middle and lower reaches of the Yangtze River, this paper summarizes the control factors of the barrier river section including the single meandering river channel morphology, the upper middle part of the middle reaches of the river Pick flow node; river coefficient is less than 4; river vertical ratio drop greater than 1.2 ?; clay shore clay content is higher than 9.5%; bed median diameter of more than 0.158 mm and so on. Based on the Navier-Stokes equations, the expression of bending radius of river flow axis is deduced, and then the effect of each control element on the hydrodynamic axis swing and barrier river formation is analyzed. The discriminant conditions of the barrier section are as follows: the ratio of the wobbling force of water flow axis under different flow levels to the constraint of the boundary conditions of the river is always less than 1; the mechanism of action of the barrier section is that even if the upstream river potential is adjusted, The boundary can always restrain the swing amplitude of the main stream and return to the mainstream plane position under different river conditions in the upper reaches, providing a relatively stable inflow condition for the downstream river channel so as to block the upstream river potential regulation from being transferred to the downstream.