弯道水流运动是河流动力学研究的基本问题之一，长期以来，其复杂的三维水流结构一直是研究者关注的重点。弯道水流在重力及离心力的共同作用下，形成弯道螺旋流，与顺直河道相比，具有特有的运动特性，主要表现在产生水面横比降、横向环流、流速重分布等方面。用声速多普勒流速仪（ ADV ），对室内 U 形弯道水流结构进行了详细的测量，分析表明弯道环流出现了较为明显的双涡二次流变化过程。此外，试验验证结果表明雷诺应力模型（ RSM ）能较好地模拟弯道环流双涡二次变化过程，为深入分析弯道水流特性及其对泥沙运动、河床演变等影响问题提供了科学方法。

The structure of an U-shape bend flow including lateral slope of water surface, streamwise velocity, circulation flow and typical u-v vectors along water depth directions were analyzed. Velocities were measured using up  looking and down-looking Sontec-ADV (acoustic doppler velocimenters). Furthermore, the numerical modeling of bend flow has also been conducted in the experimental flume under various flow conditions. These simulated results agree well with the experimental data.