淹没垂直圆柱周围水流结构及紊流特性试验研究

Flow Patterns and Turbulence Characteristics Around a Submerged Vertical Circular Cylinder

淹没垂直圆柱虽在各工程领域中均有广泛的实际应用,但还没有关于其绕流场内水流结构及紊流特性的系统研究。通过室内变坡水槽试验对淹没垂直圆柱周围的瞬时流速场进行了精细测量,分析了淹没率对垂直圆柱上下游竖直对称面内三维流速、紊动强度等水力参数垂线分布的影响程度,研究了向下水流、马蹄形旋涡和尾流旋涡等典型水流结构的冲刷力随淹没率的变化规律,揭示了淹没率影响垂直圆柱周围清水局部冲刷的机理。研究结果表明:增大淹没率能够减小垂直圆柱出露于水体中的有效长度,使得垂直圆柱对水体的阻流和扰动作用减弱,也使得垂直圆柱上游迎水面处向下水流、柱周马蹄形旋涡和下游尾流旋涡的冲刷能力被有效削弱,降低了垂直圆柱周围床面泥沙被旋涡体系卷起后顺水流失的概率。

Although submerged vertical circular cylinders have been widely applied in engineering fields,there are no systematic study on the flow pattern and turbulence characteristics in the flow field around the submerged vertical circular cylinders.In view of this,we carried out indoor flume experiment with different slopes and accurately measured the instantaneous velocity field around the submerged vertical circular cylinders. According to the test result,we analyzed the impact of the submergence ratio on the vertical distribution of three-dimensional flow velocity and turbulence intensity along upstream and downstream vertical symmetry plane of the submerged vertical circular cylinders.On this basis,we researched the variations of scour strength of downstream flow,horseshoe vortex and tail flow vortex with submergence ratio,and revealed the mechanism of submergence ratio affecting local scour by clear water around the submerged vertical circular cylinders. Research results show that 1） increasing submergence ratio could reduce the effective length of vertical circular cylinder above water surface and weaken the resistant flow and disturbance of the cylinder on water; 2） the scour capacity of downward flow in the upstream of cylinder,horseshoe vortex around the cylinder,and tail flow vortex obviously decreases,which reduces the probability of sediment around vertical circular cylinder being eroded by vortex.