明渠水流交汇区流动特征试验研究

天然河流中存在着大量的主支交汇河流，在干支流交汇处，水流结构变得十分复杂。通过水槽试验，应用声速多普勒测速仪（ADV），观测了入汇角为30°时，支流斜接主流入汇型河道的三维水流结构。试验表明：入汇上游受支流顶托影响，产生一定的壅水，出现低速区，而对侧由于束水作用产生高速区。在入汇一侧下游较短的距离，产生回流现象，并形成分离区，而在下游一定范围内，靠支流入汇侧出现水流高速区，并形成二次流结构。交汇区水流流动主要有水流分离区、高流速带、低流速带及剪切面等。

Experimental Study on Flow Structure at Open Channel Confluences

Channel confluences are common in natural rivers and many hydraulic engineering projects.The flow structure at confluences become very complex because of the interaction between tributary and Main River. The experiments were performed in a combined flume with 30° angle between main and tributary flume located at Sichuan University. The velocity was measured using a three component Acoustic Doppler Velocimeter (ADV) over a grid defined throughout the junction region. Based on the analysis of the velocity at confluence, the distinctive characteristics of a channel confluence flow may be divided into several zones including a zone of separation immediately downstream of the junction branch channel, a maximum and minimum velocity region at upstream and downstream in the confluent channel, and a shear plane developed between the two combining flows at downstream of confluent channel. In addition, there are different direction secondary circulations at the high and low velocity zone.