弯曲河岸侧向潜流交换试验

为揭示河岸形态引起的侧向潜流交换规律,利用地表水与地下水双循环水槽系统,通过10组正弦型微弯河岸与4组直线型河岸的潜流交换对比试验,研究不同河岸振幅a、地表水流速u、河流水深h条件下的潜流交换特性。试验结果表明,与垂向潜流交换机理类似,侧向潜流交换也存在对流(泵吸交换)、扩散和微循环3种交换形式。河流雷诺数Re的增大,将加强紊动扩散与微循环作用。河岸弯曲形态的出现,将引起泵吸效应,大大加剧了河岸的潜流交换,且随着河岸振幅与河流流速的增大,河岸形态引起的泵吸交换将逐渐成为潜流交换前期的主要形式。

Laboratory experiments on lateral hyporheic exchange in riverbanks with curved bank morphology

As an important component of stream-subsurface exchange processes, lateral hyporheic exchange plays a crucial role in maintaining health of river and riparian ecosystems. In order to reveal the discipline of lateral hyporheic exchange induced by bank morphology, 10 runs of circulation flume experiments with idealized sinusoidal curved bank and 4 runs of comparison experiments with straight bank were conducted in varying flow conditions. The experimental results showed that the lateral hyporheic exchange also consisted of advection (pumping exchange), diffusion and micro-circulation, which was similar to the vertical hyporheic exchange. The increasing stream Reynolds Number Re intensified the effect of diffusion and micro-circulation. The presence of curved bank morphologies produced additional exchange under all flow conditions. With increasing bank amplitude and flow velocity, the pumping exchange (advective exchange) gradually became the main exchange pattern in the earth time of hyporheic exchange.