Abstract The dispersion coefficient is the most crucial parameter that governs the model prediction of pollutant mixing in rivers. However, the spatial variability of dispersion coefficient associated with velocity structures has not yet been thoroughly investigated. In this study, two types of spatially varying dispersion tensors were considered using both the vertical velocity profiles (DF) and the depth-averaged flow fields (DA), and the pollutant transports using DF and DA were compared with tracer test results in a meandering channel. The results showed that the peak concentration and arrival time were more accurately predicted by using DF than DA, because the flow properties associated with the shear induced dispersion were explicitly incorporated in the DF. The spatial distributions of the DF showed variations in both stream-wise and span-wise directions due to the creation and destruction of secondary flow in the meandering channel. In contrast, the DA only changed in the stream-wise direction. Therefore, the DF is advantageous to reproduce shear dispersion processes.

中文翻译：

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基于垂直速度剖面和深度平均流场的空间变化色散张量的实验和数值研究

摘要 弥散系数是控制河流污染物混合模型预测的最关键参数。然而，与速度结构相关的色散系数的空间变异性尚未得到彻底研究。在这项研究中，使用垂直速度剖面 (DF) 和深度平均流场 (DA) 考虑了两种空间变化的色散张量，并将使用 DF 和 DA 的污染物传输与蜿蜒曲折的示踪剂测试结果进行了比较渠道。结果表明，与 DA 相比，使用 DF 可以更准确地预测峰值浓度和到达时间，因为与剪切引起的分散相关的流动特性明确地包含在 DF 中。由于蜿蜒通道中二次流的产生和破坏，DF的空间分布在流向和展向方向上都表现出变化。相比之下，DA 仅在流向方向上发生变化。因此，DF 有利于重现剪切分散过程。