河宽渐变水流运动对河床冲淤特性影响的数值分析

天然河道受水沙条件、堤防工程等因素的影响，其平面形态常呈现河道拓宽与缩窄的特征。本文以宽窄渐变河段的洪水过程与典型断面冲淤变化特性为基础，利用数值模型探讨了河宽渐变对水流运动特性的影响，并进一步分析了局部区域冲淤的水动力机理。分析结果表明：不同的洪水过程峰量大小及历时特征，将显著影响其涨退水强度；不对称的河道拓宽与缩窄，将改变断面流速峰值的分布；河床断面的冲淤特性取决于洪水过程的流速变化与床沙起动流速的大小。

Numerical Study on the Effects of Flow Motion on Channel Evolution in Gradual Width River

The wide gradual reach is a common form of natural rivers because of the impacts of flow and sediment conditions, and man-made projects. Based on the flood process and erosion and deposition of hydrological observational cross section in a gradual width river, the hydrodynamic characteristics have been simulated and analyzed by means of a two-dimensional flow model. The comparison between observation and simulation show that the intensities of increase and decrease of flood depend on the value and duration of flood process, the velocity distribution at any cross section often change with the variation of asymmetry river wide, furthermore, which affects the bed deformation in the whole reach considering the effect of sediment critical incipient velocity.