180°弯道水槽表面流速分布研究

On the Distribution of Surface Flow Velocity in 180°Curved Open Channel

自然界中河流多是弯曲的,弯道水流结构分析是水力学及河流动力学最重要的课题之一,对河道管理和河流开发利用也有着重要意义。基于粒子跟踪测速(particle track velocimetry,PTV)技术对180°弯道水槽不同流量下的水流表面流速进行测量与分析。试验结果表明:除进口断面,凹岸侧表面纵向流速均大于凸岸侧表面纵向流速,中心线上的表面纵向流速沿程变化相对较小;水流进入弯道后,凸岸的水流开始向凹岸方向运动从而产生横向流速,当水流流过弯顶后,由凸岸向凹岸的横向运动逐渐消失。对比两个流量的流速分布结果,较小流量下表面水流的“顶冲点”发生在弯顶前,较大流量下表面水流的“顶冲点”发生在弯顶后,较小流量下的凸岸侧水流更容易向凹岸方向运动。

Rivers are mostly curved in nature.Analysis of the flow structure of curved channels is one of important topics of studies in hydraulics and river dynamics,and is of great significance to river management and development.The surface velocity of water flow at different flow discharge in the 180°curved open channel flume was measured and analyzed based on the particle track velocimetry(PTV)technology.The test results show that,except for the inlet section,the surface longitudinal velocity of the concave was greater than that of the convex,and the surface longitudinal flow velocity on the center line changed relatively little along the channel flume.After water flow entered the bend,the surface water flow of the convex began to move toward the concave and generate a lateral velocity.When water flows passed the top of the bend,the lateral movement of the convex toward the concave gradually disappeared.Large and small flows discharges were applied and measured.The velocity distributions of the two discharges show that,the scouring point of the surface water flow in the small flow discharge occurred before the curved top,while it occurred after the curved top in the large flow discharge.The water flow on the convex was more likely to flow toward the concave in the small flow discharge.