Hydrodynamics and contaminant transport on a degraded bed at a 90-degree channel confluence
Hydrodynamics and contaminant transport on a degraded bed at a 90-degree channel confluence
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DOI：
10.1007/s10652-017-9562-8
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发表时间：
2018-04
影响因子：
2.2
通讯作者：
Hongwu Tang;Huiming Zhang;Saiyu Yuan
中科院分区：
文献类型：
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作者：
Hongwu Tang;Huiming Zhang;Saiyu Yuan
河道汇流对天然河道和人工渠道的动量交换和污染物扩散有重要影响。在这项研究中，一个三维的数值模型，这是基于雷诺平均Navier-Stokes方程和雷诺应力湍流模型，模拟和比较不同的床形态的流动模式和污染物的传输过程。结果表明，污染物浓度的分布主要受剪切层和两个反向旋转的螺旋单元的控制，而剪切层和螺旋单元又受流量比和床层形态的影响。随着流量比的增大，剪切流向外侧流动，由流动偏转引起的逆时针支流螺旋胞扩大，导致外侧发生混合，混合层发生畸变。床面形态的变化会导致分流区的收缩和主槽顺时针螺旋单元的增加，这是由支流螺旋单元与主槽水流的相互作用引发的，并被深冲坑强化。床层形态也会影响混合层的变形方向。大流量比和床层形态均能提高混合强度。
Channel confluences at which two channels merge have an important effect on momentum exchange and contaminant diffusion in both natural rivers and artificial canals. In this study, a three-dimensional numerical model, which is based on the Reynolds Averaged Navier–Stokes equations and Reynolds Stress Turbulence model, is applied to simulate and compare flow patterns and contaminant transport processes for different bed morphologies. The results clearly show that the distribution of contaminant concentrations is mainly controlled by the shear layer and two counter-rotating helical cells, which in turn are affected by the discharge ratio and the bed morphology. As the discharge ratio increases, the shear flow moves to the outer bank and the counter-clockwise tributary helical cell caused by flow deflection is enlarged, leading the mixing happens near the outer bank and the mixing layer distorted. The bed morphology can induce shrinkage of the separation zone and increase of the clockwise main channel helical cell, which is initiated by the interaction between the tributary helical cell and the main channel flow and strengthened by the deep scour hole. The bed morphology can also affect the distortion direction of the mixing layer. Both a large discharge ratio and the bed morphology could lead to an increase in mixing intensity.