资源环境科技发展态势分析平台

For dyes or solutes in still water, the diffusion process is known to be driven by their concentration gradients and can be described using the memoryless Brownian motion process. Such a process can model the irregular movement of small particles without temporal correlation. In the conventional analysis, the random movement of fine sediment particles in open‐channel flow is modeled using an advection‐diffusion equation with the memoryless Brownian motion process as the particle diffusion term. However, when particles transport within time‐persistent turbulent flow structures, the movements of the suspended particles may exhibit persistency that depends on the various temporal durations of turbulent flow structures. Such persistence results in the variations of particle velocity in both value and direction of a moving fine particle. Accordingly, the diffusion property of the particles may deviate from normal diffusion. This study proposes a stochastic process based on random walk model theory to represent the temporal correlation in suspended sediment particle velocity caused by turbulent structures in open‐channel flow. Numerical simulations indicate that despite its local superdiffusion behavior, a particle exhibits normal diffusive behavior when the observation time scale is larger than the maximum duration of the turbulent events. The effective diffusion coefficient of the proposed stochastic process is formulated.

This article is protected by copyright. All rights reserved.