含滩地交汇河道水动力特性与掺混特征数值模拟

为研究滩地对河道交汇区水动力特性以及物质输移的影响，建立了含滩地河道交汇区的三维水动力-污染物耦合数值模型，模拟并分析了不同高度和宽度的滩地对交汇区水流结构及污染物横向掺混的影响。研究结果表明：支汊滩地引起的侧向入流垂向动量重分布，对交汇区的双螺旋流结构，污染物横向扩散范围以及掺混层的位置、形态特征和宽度等均有显著影响；支流侧二次流强度和范围随着滩地高度的增加而增大，滩地展宽使支流侧二次流向左岸偏移、强度增大；污染物混合程度与二次流密切相关，二次流的强度、位置和范围均对物质掺混速率有重要的影响，二次流的强度越高、范围越大、位置越接近掺混层，污染物掺混速率越快。

Hydrodynamic and mixing characteristics of river confluence with floodplain

In order to study the effect of floodplain on the flow characteristics and pollutant transport of river confluence, a three-dimensional hydrodynamic and pollutant coupled numerical model is established to simulate and analyze the effects of floodplain with different heights and widths on the flow structure and transverse mixing characteristics of pollutants in the confluence in this study. The results show that the vertical momentum redistribution of the lateral inflow, which is caused by the floodplain, has a significant influence on the structure of the twin-helical flow, the transverse advection range of pollutants, and the position, morphological characteristics and width of the mixing layer. The intensity and range of the secondary flow increase with the increase of floodplain height. The widening of the floodplain makes the secondary flow deviate from the left bank and its intensity increases. In addition, the mixing degree of pollutant is closely related to the secondary flow, i.e., theintensity, location and range of secondary flow;the higher intensity, the largerrange and the closerpositionto the mixing layer can result in the faster the material mixing rate.