Stochastic Modeling for Anomalous Suspended Sediment Transport

Abstract

Studies have categorized turbulent bursting events into outward interactions, ejections, inward interactions, and sweeps. Among these events, ejections and sweeps contribute notably to the time consumption, momentum flux, and sediment flux. Studies have reported that the distribution of turbulent coherent structures is uniform. However, research has revealed that the distribution of bursting events is nonuniform at different bed elevations. Although the nonuniform distribution of turbulent bursting events has been investigated, their influence on sediment transport has yet to be examined. This study established an improved stochastic diffusion particle tracking model (SD-PTM) using the stochastic Lagrangian method to describe sediment particle movement. This model integrates turbulent characteristics determined using a direct numerical simulation data set for comprehensively analyzing the sediment particle motion during turbulent flow. We developed a modified SD-PTM that considers the nonuniform spatial distribution of ejection and sweep events and the particle movement direction during these events. Particle trajectories were obtained using this model, and the anomalous diffusion during sediment transport was analyzed by calculating the variance in the particle trajectories. The performance of the proposed model was evaluated by comparing the flow velocities and sediment concentration profiles obtained using it with those measured in previous studies. Therefore, the sediment particle motion during turbulent flow was comprehensively investigated under extreme flow conditions.