地理学报 ›› 1994, Vol. 61 ›› Issue (5): 430-439.doi: 10.11821/xb199405005

• 论文 • 上一篇    下一篇

冲积河流的汇合与分流

高进   

  1. 湘潭矿业学院资源勘察与市政工程系, 湘潭 411201
  • 出版日期:1994-09-15 发布日期:1994-09-15

THE CONFLUENCE AND DIVISION FLOWS IN RIVER CHANNEL

Gao Jin   

  1. Xiangtan Mining Institute,Department of Resource Exploration and Municipal Engineering.411201
  • Online:1994-09-15 Published:1994-09-15

摘要: 冲积河流具有一定的自动调整作用。遵循最小阻力原理,河道的汇合分流也应属于冲积河流的自动调整作用之列,事实上,在河道的汇合与分流处,支流与主流夹角的形成及其宽度比(或断面积比)的建立都不是随机的,它必须保证来自支流与主流的水和泥沙能在此通畅排泄。本文证明了水流在通过河道的汇合与分流处时所形成的夹角及其宽度比,对应于水头损失的最小值。河口段垂直于或趋向垂直于海岸线的特性,也是水流不断调整到最小阻力状态的结果。

关键词: 冲积河流, 汇合, 分流, 河口, 最小阻力原理

Abstract: Alluvial river has a capability of automatic regulation.One problem which should be noticed is that the confluence and divison flows in river channel also have some effects of automatic regulation and follow the principle of the least resistance.In fact,the forming of the angles of the confluence and divison flows in river channel and the constitution of their width ratio (or their area ratio of cross section)for tributary and main current are all not random,they should ensure that the water and sediments in tributary and main currents can be drained freely.In this paper,a few problems are described.River mouth 1.When the water flow passes through the place where there are confluence and divison flowsin river channel an intersecting angle and their width ratio (or their area ratio of cross section) areformed,which correspond to the minimum value of head loss.Under turbulent flow the angle canbe worked out as follows:cosθ=(b1/b2)5(1+2(Q2/Q1))where the cross section of rive channel is supposed to be arc,the b1/b2is a specific value of riverwidth for tributary and main current.the Q2/Q1is a specific value of discharge for main current andtributary.when their water flow velocity is the same,we can get:cosθ=(b1/b2)5+2(b1/b2)3 When b1/b2=1/3 θ= 85°31’When b1/b2=1/5 θ=89°3’ So the angles of confluence and divison flows in general river channels are nearly right. 2.The calculated value is 62°23’ which is the angle of divison flow in the Shiyezhou branch ofthe Changjiang river and the real angle is approximately 60°.Both are nearly the same.3.At the place where there are confluence and divison flows in river channel,the functional relation between hydrodynamical essential factor and formal essential factor may be constituted andcan be expressed as follows: Q2/Q1=1/2[cosθ/((b1/b2)5)-1] or Q2/Q1=1/2[cosθ/((ω12)5)-1]Where is a specific value of the area of cross section for tributary and main currents.When the discharge ratio Q2/Q1changes,at the place with confluence and divison flows ,the intersecting angle and the width ratio(or their area ratio of cross section) for tributary and main currentsneed to be regulated.so that water flow may attain the condition of least resistance.4.The angle θ of confluence and divison flows in river channel are not greater than 90°.Becauseit can not meet the least resistance principle.5.Usually,the segment of river mouth is at a right angle or tend to be right with the line ofsea bank.River flows into the sea can be regarded as that the tributary with finite width (or finitearea of cross section) flows into the main current with infinite width (or infinite area of crosssection).The intersecting angles tend inevitably to be 90°.The characteristic of the strike of the segment of river mouth is also resulted from the fact that the water flow regulates constantly to attainthe condition of least resistance.

Key words: Alluvial, Confluence, Division flows, The principle of the least resistance, River mouth