资源环境科技发展态势分析平台

In conventional analysis of sedimentation in open channel flow, suspended sediment transport is regarded as an advection diffusion process. A series of theories based on Brownian motion are developed for describing the diffusion process of sediment particles attributed to turbulence. However, difficulties remain because these models cannot represent the time coherence of turbulence structures that affect instantaneous local sediment concentrations. Focusing on the impact of two flow structures in the near-wall region on suspended sediment transport, ejection, and sweep events, this study proposes a new stochastic Lagrangian model to simulate sediment particle trajectory. While the occurrences of ejection/sweep events are confirmed to change the instantaneous sediment flux, their impact on the long-term average sediment flux has yet to be confirmed. The simulation results identify the contributions of these structures to suspended sediment transport and show that the time coherence of flow velocity may be essential for flow to carry sediment particles in suspension. This study also points out that the duration of the flow events may be the key to interpret the diffusion coefficient in terms of turbulence intensity.