The accumulation of sediments within mountainous gullies serves as a significant source for the main channel. Understanding the transport characteristics is crucial for comprehending reach-scale sediment supply features and channel morphodynamics. This study addresses the previously unexplored challenges in accurately quantifying variations in sediment transport rates, particularly during critical transitions such as the mobilization of static sediment pulses into continuous motion. To accomplish this objective, a combined Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) computational framework is employed to directly simulate the detailed trajectories of all particles. After validating the CFD-DEM model, we examine the effects of three major influential factors (particle size, channel slope and channel width) on sediment transport characteristics. The results indicate that the sediment transport rate exhibits rapid rise to peak followed by gradual attenuation process, described by a long-tail effect. The cross-sectional averaged sediment transport rate positively correlates with the width of sediment transport belt. The downstream propagation of sediment is enhanced by steeper channel slope and narrower channel width. In addition, we find that cross-sectional averaged sediment transport rate controlled by these factors exhibits inherent self-similarity. The temporal variation of dimensionless sediment transport rate for a certain section can be modeled by a modified two-branch Weibull function encompasses three model parameters dependent on influential factors and longitudinal location. The parameter variation of the functional model, combined with linear variation of the three main influencing factors, provides support for explaining sediment transport processes in channels of dimensions different from those studied. These findings enhance the understanding of the formation and evolution mechanism of sediment transport induced by upstream loose deposit destruction.

中文翻译：

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基于CFD-DEM的陡峭支流补充的主河道泥沙输运过程评估

山地沟壑内沉积物的堆积是主河道的重要来源。了解输运特征对于理解河段沉积物供应特征和河道形态动力学至关重要。这项研究解决了以前未探索过的挑战，即准确量化沉积物输送速率的变化，特别是在关键转变期间，例如将静态沉积物脉冲调动为连续运动。为了实现这一目标，采用计算流体动力学和离散元法 (CFD-DEM) 相结合的计算框架来直接模拟所有粒子的详细轨迹。在验证CFD-DEM模型后，我们考察了三个主要影响因素（粒径、河道坡度和河道宽度）对泥沙输运特性的影响。结果表明，泥沙输运速率呈现出快速上升到峰值然后逐渐衰减的过程，用长尾效应来描述。断面平均输沙率与输沙带宽度呈正相关。较陡的河道坡度和较窄的河道宽度增强了沉积物的下游传播。此外，我们发现受这些因素控制的横截面平均泥沙输运速率表现出固有的自相似性。某个部分的无量纲泥沙输送速率的时间变化可以通过修改的两分支威布尔函数来建模，该函数包含取决于影响因素和纵向位置的三个模型参数。函数模型的参数变化与三个主要影响因素的线性变化相结合，为解释与研究尺寸不同的河道中泥沙输运过程提供了支持。这些发现增强了对上游松散沉积物破坏引起的沉积物输送形成和演化机制的理解。