180°弯道水槽表面流速分布研究

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.

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

Rivers are mostly curved in nature. Analysis of the flow structure of curved channels is one of the most important topics in hydraulics and river dynamics. It is also of great significance to river management and river development. In this study, the surface velocity of the water flow at different flow discharge in the 180 ° curved open channel flume was measured and analyzed based on the PTV technology. The test results show that, except for the inlet section, the surface longitudinal velocity of the concave is greater than that of the convex, and the surface longitudinal flow velocity on the center line changes relatively little along the way . After the water flow enters the bend, the surface water flow of the convex begins to move toward the concave to generate a lateral velocity. When the water flows past the top of the bend, the lateral movement of the convex toward the concave gradually disappears. Comparing the velocity distribution results of the two flow discharge, the scouring point of the surface water flow at a smaller flow discharge occurs before the curved top, and that occurs after the curved top at a larger flow discharge. The water flow on the convex is more likely to flow toward the concave at a smaller flow discharge.