Reasonable estimates of longitudinal dispersion coefficients are essential for predicting solute dispersion processes. However, the current knowledge of solute dispersion processes in vegetated waters is limited. In this work, we coupled a refined hydrodynamic model with scalar transport equations to simulate the flow field and dispersion process of solutes in water under the effect of vegetation. First, the proposed numerical model was verified using laboratory experiments, revealing the excellent performance of the coupled model in complex conditions. Eight different cases were subsequently simulated to analyse the effects of the upstream flow rate and vegetation height on the streamwise velocity, solute concentration, and longitudinal dispersion coefficients. The simulation results show that the upstream flow variation exerts a marked effect on the streamwise velocity and flow field within the vegetation zone, with a velocity difference within the shear layer reaching 54.7 % for an upstream flow of 0.018 m3·s-1. The height of the vegetation affects both the velocity profile and solute dispersion. Placing emergent vegetation upstream can enhance solute dispersion in the longitudinal direction. The correlation analysis reveals that the longitudinal dispersion coefficients obtained using the routing producer are close to those determined using the theoretical method, with correlation coefficients reaching 0.75. This work presents the appropriate application range and parameters that must be considered in deriving formulas for longitudinal dispersion coefficients.

中文翻译：

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植被流中溶质输运和纵向扩散系数的数值分析


纵向分散系数的合理估计对于预测溶质分散过程至关重要。然而，目前对植被水域中溶质分散过程的了解是有限的。在这项工作中，我们将精细的水动力学模型与标量输运方程耦合，以模拟植被作用下溶质在水中的流场和分散过程。首先，通过室内实验验证了所提出的数值模型，揭示了耦合模型在复杂条件下的优异性能。随后模拟了 8 种不同的情况，以分析上游流速和植被高度对流速、溶质浓度和纵向分散系数的影响。模拟结果表明，上游流变对植被区内的流速和流场有显著影响，当上游流速为0.018 m3·s-1时，剪切层内的速度差达到54.7 %。植被的高度会影响速度分布和溶质分散。将新兴植被置于上游可以增强溶质在纵向上的分散。相关性分析表明，使用 routing producer 获得的纵向色散系数与使用理论方法确定的接近，相关系数达到 0.75。这项工作提出了在推导纵向色散系数公式时必须考虑的适当应用范围和参数。