Abstract
The flood propagation at a confluence of channels exhibits a unique routing pattern, while there are few studies on the routing of dam-break flow in confluent channels. In this study, we conducted physical experiments and a numerical simulation to investigate the influence of different confluence angles on the routing of a dam-break flood. Experiments were carried out in smooth, transparent, rectangular prismatic channels to study the dam-break flow under four different confluence angles. The flow velocity was measured using an image processing technique, and the surface flow field was effectively captured by synchronously recording the particle motion images. Based on the variation of the water level and flow discharge, as the confluence angle increased, the retardation and abatement effects on the flood increased. Specifically, the flood arrival time was delayed by approximately 0.91% to 21.18%, and the peak flood discharge was reduced by approximately 9.05% to 58.36%. Combined with the surface flow field at the confluence and in the downstream sections, as the confluence angle increased, the impact points at the confluence and in the downstream straight sections moved upward, and the impact range was reduced. Combined with the pressure variation pattern, the routing of dam-break flow in the confluent channels experienced a process of impact-reflection-return-attenuation.
Highlights
River confluence is commonly found in natural rivers, with complex flow conditions at the confluence area
When a hydroelectric dam constructed upstream of a river breaks under a dangerous situation, the large amount of water stored in the reservoir forms a dam-break flood whose routing along the natural courses of the river leads to catastrophic damage to towns and infrastructure on both sides of the river
Based on the complexity of dam-break flood propagation and the severity of its consequences, some researchers have carried out a series of studies on the hydraulic characteristics of dam-break flood routing and flood propagation in confluence channel to reduce the risk of dam-break floods
Summary
River confluence is commonly found in natural rivers, with complex flow conditions at the confluence area. Different from ordinary floods, the dam-breaking floods happen very suddenly and quickly, and the wave peak value and peak flow discharge are several times that of rainstorm floods. Due to the complex boundary conditions of the river confluence area, the hydraulic factors such as the flow field and water depth of a dam-break flood vary in this area, resulting in unique hydraulic phenomena [1,2]. Such as secondary flow, spiral flow, local flow stagnation, separation, and water superelevation, thereby leading to a routing pattern that is very different from that in a single river channel. Lauber and Hager [3,4] conducted a dam-break wave experiment in a horizontal channel to investigate the
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