小宽深比U型弯道环流试验研究

采用多普勒超声测速仪(ADV),对小宽深比的U型弯道沿程断面上各不同垂线位置上的点进行了三维流速测量,并基于所测数据分析了主流线位置、横向流速沿垂线分布、环流结构以及环流强度等水力特性。研究结果表明:在60°断面后,水流的表层与底层主流线开始分离,形成复杂螺旋结构。水流进入弯道后,沿程各断面均形成一逆时针主环流,并且从75°断面开始,凹岸表层又出现与主环流方向相反的次生环流;环流强度最大值位置出现在弯道弯曲度1/3处附近。研究结果为进一步深入研究弯道水流紊动特性和泥沙运动提供了有效参考。

Experimental study on circulation flow of U shape channel bend with small width depth ratio

With Doppler velocimeter （ADV），3-D flow velocities on all the point of various vertical locations at the cross section along the U shape channel bend with small width depth ratio are measured，and then the hydraulic characteristics of the location of the main stream line，the vertical distribution of the transverse flow velocity，the structure of circulation flow，the strength of circulation flow，etc. are analyzed according to the measured data. The study result shows that the surface main stream flow and the bottom main stream flow begin to separate from each other after the cross section of 60°and then form a complicated helical structure. After water flowing into the channel bend，an anticlockwise main circulation flow is created，furthermore，a secondary circulation flow appears at the surface of the concave bank in the direction opposite to the main circulation flow from the cross section of 75°，while the location with the maximum strength value of the circulation flow occurs at 1/3 of the curvature of the bend. The study result provides an effective reference for the further deep study on the turbulence characteristics and sediment movement of channelbend.