Effect of particle viscosity on velocity profiles in open channel flows.

Lei Zhang, Deyu Zhong, Baosheng Wu

Thursday 2 july 2015

9:30 - 9:45h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling

Parallel session: 10A. Sediment - Transport

It is well known that the suspended sediments alter the structure of the turbulent flow by which they are carried, which in turn has a significant influence on the transport of sediments. The interaction between the particles and flows affects the properties of the sediment-laden flows. In this paper, the effect of particle viscosity on the velocity profiles of water-sediment mixtures was studied based on the two-phase mixture model. The relation for the viscosity of mixtures is composed of the fluid viscosity and the particle viscosity. The particle viscosity expression obviously reflects the effects of collisions between particles and particle turbulence as the basic feature of two-phase flows. Good performance is shown in comparison with the laboratory observations of Einstein and Chien (1955) and Wang and Qian (1992). Furthermore, the distributions of the contributions of different factor to the mixture viscosity in the vertical direction were also analyzed. Results show that when the particle inertia is quite small, the effect of the fluid viscosity is dominant; with the increasing of the particle inertia, the effect of the particle viscosity, especially the particle turbulence, generally becomes the dominant mechanism near the bed surface for the velocity distribution of mixtures. We hope our work is helpful to deeply understand the mechanism of the sediment-laden flows in open channels.