Author(s): Xudong Fu; Guangqian Wang
Linked Author(s): Xudong Fu, Guangqian Wang
Keywords: Crossing trajectories; Diffusivity; Inertia; Kinetic model; Open-channel flow; Suspended sediment; Turbulence
Abstract: Knowledge of vertical diffusion of suspended sediment is essential for reasonably determining suspended-sediment transport in open-channel flows. Conflicting evidences on the relationship between sediment diffusivity and fluid eddy viscosity have advanced two- phase formulations of sediment-laden flows in recent years. However, no effort has been made to examine the assumptions that are introduced into modeling the fluid Lagrangian integral timescale seen by suspended sediment. This paper examined three existing formulations of this timescale through a kinetic-model-based simulation of sediment vertical diffusion. Model predictions were compared against Graf and Cellino’s (2002) experimental data. Reasonable agreements could be achieved for Model 3 that accounts for both the inertia and crossing trajectories effects. This suggested that the kinetic model coupled with a reasonable formulation of this timescale could satisfy the requirements of quantifying various effects on sediment vertical diffusion. On the other hand, the fluid Lagrangian integral timescale seen by suspended sediment plays an essential role in characterizing sediment vertical diffusion. Further exploration of turbulence structure of the carrier water would be desired for improving characterization of sediment diffusion process.
Year: 2005