河宽渐变是天然河道的普遍形态特征。运用声学多普勒流速仪（ADV）测量了渐变河道模型的水流结构。试验结果表明：渐变河道形态对水流结构影响明显，在渐缩段和渐扩段产生二次环流，前者影响效应大于后者，且方向相反。基于 SMS 水动力学模型对渐变河道水流特性进行了二维数值模拟，与实测值吻合较好，并计算分析了局部水头损失系数沿程的变化规律。

The gradual change of transition channel width is a common form of natural rivers. The flow structure of transition channel was measured in the physical model by Acoustic Doppler Velocimeter (ADV). It is manifested that the flow was influenced remarkably by the streamwise velocity. Secondary circulation was induced in the gradually shrinked section and in the gradually expanded section, with the circulation effect in the former greater than the latter in an opposite direction. According to the 2-D flow simulation by SMS hydrodynamic model, the coefficient of local head loss was proved to be consistent with the measured value, and the coefficient values at flow separation zone were times larger than that in other regions.