题目 Title

Response of flow and saltating particle characteristics to bed roughness and particle spatial density.

期刊 Journal

Water Resources Research (IF=5.24)

作者 Author

Zhao CW; Ouro P; Stoesser T; Dey S; Fang HW

摘要 Abstract

With the goal to explore the effects of natural bed roughness on bedload transport, numerical simulations of flow and particle saltation are carried out with varying bed roughness and particle spatial density. A combination of Eulerian and Lagrangian point-particle methods is applied to solve the equations of motion of the fluid and the particles within the large-eddy simulation framework. Flows over smooth and rough beds with four particle densities are considered. As the bed roughness increases, there is a leftward shift of the double-averaged streamwise velocity profiles against dimensionless vertical distance, which is scaled with the bed roughness height, an upward shift of the peak values of double-averaged Reynolds stresses, and a fragmentation and disappearance of coherent structures in the form of high-speed and low-speed near-bed streaks. These observations are consistent with those of previous studies. As the bed roughness increases, the mean resting time of saltating particles increases, however the particles' saltation length, velocity, and angular velocity decrease, while their saltation height remains almost unchanged. Saltation height, saltation length, particle angular velocity, and resting time exhibit linear, gamma, normal, and exponential distributions, respectively. Further, as the bed roughness increases, the kurtosis and skewness of some particle parameters vary, and the particle velocity shifts from a symmetrical normal to an asymmetrical gamma distribution.

简介 Brief introduction

本文为了探索天然床面粗糙度对推移质输移的影响，依据天然河流中河床的粗糙度特征，生成了符合高程统计规律的粗糙床面，并以推移质泥沙颗粒为研究对象，采用精细的大涡模拟计算，通过水流-泥沙双向耦合的欧拉-拉格朗日方法，针对对应于紊流光滑区、过渡粗糙区和完全粗糙区的三类水流流动和推移质颗粒跃移进行了数值模拟，分析了不同床面粗糙度对近床湍流结构、推移质跃移参数及输沙能力的影响。研究发现了随着床面粗糙度的增加，推移质颗粒停留时间增加，跃移长度、速度和旋转速度显著减小，跃移高度没有明显的变化。光滑床面跃移高度、长度、旋转速度和停留时间的概率密度分布分别服从线性、伽马、正态和指数分布。随床面粗糙度的增加，曲线的峰度和偏度发生变化，跃移速度由对称的正态分布转变为不对称的伽马分布。推移质输沙率与粗糙度雷诺数呈负相关关系。

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