为探讨溢流坝壅水条件下的弯道水流特性,概化设计了一在出口处布设有溢流坝的连续弯道模型,利用声学多普勒流速仪(ADV)和数字波高仪测得模型特征断面的流速、水位数据。试验结果显示:弯段绝对水面横比降随相对坝高的增大而减小;弯段下半弯的水面纵比降为正,而从直线过渡段进口至下游邻近弯顶的水面纵比降为负,但其绝对水面纵比降均随相对坝高的增大而减小;连续弯道的直线过渡段也存在二次流且其旋转方向与上游弯段二次流的旋转方向相同;当相对坝高增大时,流道各断面的垂线平均纵向流速均不同程度的减小;当相对坝高增大时,各断面最大紊动能减小;纵向脉动对紊动能的贡献最大,横向脉动次之,垂向脉动最小;雷诺应力R_uv的正负能近似标示弯道直线过渡段进出口断面的横向水流运动,当雷诺应力R_uv为正时,流体将从左侧流向右侧;当雷诺应力R_uv为负时,流体将从右侧流向左侧。

To investigate the flow characteristics in meandering channels under backwater conditions caused by overflow dams, a meandering channel model with an overflow dam at its outlet is designed and constructed. Velocity and water level data in thirteen cross sections are measured using an Acoustic Doppler Velocimeter (ADV) and a digital water level altimeter. The experimental results demonstrate that the absolute transverse water surface gradients in curved segments decrease as the relative dam height increases. The longitudinal water surface gradients between a bending apex and the inlet of the downstream adjacent crossover area exhibit positive values, while the longitudinal water surface gradients between the inlet of a crossover area and the downstream adjacent bending apex display negative values. Nevertheless, the magnitudes of these gradients diminish with the increasing relative dam height. Moreover, secondary flow vortex blobs are observed in the crossover areas of the meandering channel, rotating in the same direction as those in the upstream adjacent curved segment. With an increase in relative dam height, the depth-averaged longitudinal velocities along the meandering channel decrease to varying extents. Likewise, the maximum turbulent kinetic energy in any cross section decreases as the relative dam height increases. Regarding the distribution of turbulent kinetic energy, the longitudinal velocity fluctuation contributes the most, followed by the transverse velocity fluctuation, while the vertical velocity fluctuation contributes the least. The Reynolds stress (R_uv) can be used as an approximate indicator of the directions of cross-sectional transverse flow movements at the inlets and outlets of the crossover areas. If the Reynolds stress value is positive in a specific region, the fluid will flow from left to right; otherwise, the fluid will flow from right to left.