Modeling suspended sediment transport under the influence of attached eddies in turbulent flows.

Eddies affect the motion of particles within the turbulence boundary layer on different length and velocity scales. Attached eddies, which extend to the wall, are primarily responsible for most of the turbulent kinetic energy and Reynolds shear stresses in the turbulence boundary layer. The attached eddies can be devided into two types: type-A eddies are directly attached to the wall, while type-B eddies are not. The physical characteristics of type-A and type-B eddies are quite distinct, as such their individual effect on sediment particle movement should be more precisely considered in sediment transport modeling. This study combines the attached eddies hypothesis with the stochastic diffusion particle tracking model (SD-PTM) to simulate suspended sediment particle transport in a turbulence boundary layer under the influence of attached eddies. Sediment particles in turbulent flow not only move with the mean drift but also diffuse randomly due to turbulence. Hence, the trajectory of such particles is treated as governed by a stochastic process in this study. The proposed model, incorporating the detailed properties of type-A and type-B eddies, presents an eddy-constrained random walk (ECRW) that describes the circular motion of flow in turbulence. The proposed model is verified using the concentration profile obtained from available data. The ensemble means and variances of particle trajectories can be obtained. Anomalous diffusion of sediment particles under the effect of attached eddies and the contributions of type-A and type-B eddies to sediment particle movement are discussed. [ABSTRACT FROM AUTHOR]