An Experimental Study on the Influence of Drastically Varying Discharge Ratios on Bed Topography and Flow Structure at Urban Channel Confluences

摘要

The confluences of rivers are important nodes for energy conversion and material transport in the river network. A slight morphological alteration of the confluences may trigger the “butterfly effect”, which will bring about changes in the ecology and environment of the entire river network. During the transition period of the wet and dry seasons, the variation of discharge ratio will make the originally balanced river bed change again, which will bring a series of follow-up effects. This research mainly studied the features of water flow itself and results showed that the variation of discharge ratio caused secondary erosion of the balanced bed surface and transported the sediment downstream. Thus, the zone of maximum velocity was enlarged and the maximum flow velocity at the equal discharge was reduced, and more intense vortex and turbulence were generated. The lateral velocity, vertical velocity, and turbulent structure were mainly controlled by the quantity and ratio of the discharge, and the varying topography only played a minor role in local areas. Nowadays, some scholars have been studying the combination of flow field features and various environmental substances and biological habitats, and the basic work done in this article has laid the foundation for these studies.