基于PIV技术的明槽交汇区流场试验研究

Experimental study on open-channel flow confluence based on PIV technology

明槽交汇水流存在于很多水力系统中,交汇区水流结构十分复杂,对干、支流交汇流场的研究具有重要意义。研究采用能突破空间单点流速测量局限的PIV技术,观测不同汇流比条件下非对称型交汇明槽的三维水流结构,分析交汇区流场的演变规律。试验结果表明,交汇口上游的水面比降随汇流比的增大而减小,交汇口处及下游合流掺混区水面比降随汇流比的增大而增大。交汇口上游各断面垂线时均流速随汇流比的增大而增大,各断面时均流速随汇流比的增加而受到顶托效应的影响越大,交汇口各断面垂线的时均流速随汇流比的减小而减小,分离区随汇流比的减小而增加。PIV技术能良好的观测交汇区水流结构,可应用于明槽交汇区的流场试验研究。

The confluence of water flow that occurs in many hydraulic systems is usually very complicated in flow structure, and an in-depth examination of its behaviors is practically significant to the study of the confluences of a river main channel and the tributaries. This study adopts the PIV technology to overcome the shortcomings of single-point velocity measurements, observes the asymmetrical 3 D flow structures of an open-channel confluence at different discharge ratios, and analyzestheir variations with the discharge ratio. Results show that with an increasing discharge ratio, water surface slope decreases upstream of the confluence, while it increases over the junction area and in its downstream. And for the depth average velocity under an increasing discharge ratio, it is increased upstream of the confluence responding to the increasing backwater effect and over the junction area, but decreased in the flow separation zone. The PIV technology can better reveal the flow structure of a flow confluence and is applicable to the experimental study of the flows in open-channel confluences.