阶梯-深潭结构的潜流交换及污染物运移模拟

Simulation of Hyporheic Exchange and Pollutant Migration in Step-pool Structures

为了揭示阶梯-深潭结构中河床污染物运移过程,以及潜流交换强度与单宽流量、坎高比的关系,探讨合适的阶梯-深潭治污工程参数,进行了多组阶梯-深潭结构潜流交换模拟。结果表明:地表水在阶梯坎上游进入河床,驱赶污染物至下游河床再排出,清洁区域自阶梯坎向上游延伸较快,当延伸至下游渐近线附近时污染物运移速度明显减缓;在相同的河床梯度和流量条件下,阶梯-深潭结构引起的潜流交换强度约为平坦河床的37倍;潜流交换强度与单宽流量、坎高比均呈幂函数关系,单宽流量和坎高比越大则潜流交换强度越大;人工引入阶梯-深潭结构时,阶梯坎高度0.4 m、间距30 m时,河床污染物治理效果较好。

In order to reveal the migration process of riverbed pollutants in the step-pool structure,and the relationship between the intensity of the hyporheic exchange and the single-wide flow and the height ratio,the appropriate step-pool pollution control engineering parameters are explored.Underwater flow simulation of steep-pool structures,the results show that the surface water enters the river bed upstream of the step ridge,driving out pollutants to the downstream river bed for discharge,and the clean area extends faster from the step ridge to the upstream.When it extends to the downstream asymptote,the migration speed of the pollutants slows down significantly.Under the conditions of riverbed gradient and flow,the intensity of the hyporheic exchange caused by the step-pool structure is about 37 times that of a flat riverbed.The intensity of the hyporheic exchange has a power function relationship with the single-wide flow and the height ratio.When the step-pool structure is artificially introduced,the step height is 0.4 m and the spacing is 30 m,the riverbed pollutant treatment works better.