Effect of particle inertia on the transport of particle-laden open channel flow

The particle inertia is a key feature affecting the transport of particle-laden, open-channel flows. In this paper, the influence of particle inertia is investigated by varying the size, density and concentration of particles in the flow. Under the framework of Reynolds-Averaged Navier-Stokes equations, a partial two-fluid flow model is developed. The partial-two fluid model offers simplification over complete two-fluid model by solving a mixture equation for the momentum equation for water. The governing equations consider particle-fluid interaction through a drag force, inter-particle collisions, dispersivity of the particles, and a K-epsilon turbulence closure. A range of particle size, density and concentration is considered in the sensitivity analysis. The results show that the particle size has significant influence on its velocity, distributed concentration in the water column and in reducing the turbulent kinetic energy. The variation in the density of particles in the flow show minor effect on the mean velocities of both phases and a slight reduction in the turbulent kinetic energy. Increase in maximum concentration of particles at the bed only affects the turbulent kinetic energy significantly; however, it does not have notable influence on the mean-velocities of both phases, and the distribution of particle concentration. The influence of particle inertia on the dispersivity of the particles in the flow is investigated by simulating the test cases of laboratory experiments. The comparison of results with the experimental data shows that the Schmidt number decreases with the increase in particle size in case of flow with high particle density. In cases of flow with low particle density, the maximum concentration of the particles at the channel bed governs the values of the Schmidt number required to match the experimental data.