Computational investigation of vertical slurry jets in water

Abstract

The characteristics of sand–water slurry jets in water were investigated by a validated numerical model. Predictions of the main properties of the jet such as axial and radial velocities and particle concentration agreed well with laboratory measurements. The effect of sand particles on slurry jet spreading rate, axial velocity decay, decay of concentration and turbulence properties was studied, and the results were compared with the corresponding single-phase water jets and plumes. It was found that the width of slurry jets grows linearly from the nozzle up to a certain distance and then the growth rate became non-linear. At particle volume concentrations larger than 2.4% or with particle sizes larger than 505μm, the spreading rate of sand phase was found to be only about one third of that of the water phase. Empirical formulations are proposed to describe the effects of controlling parameters on the axial velocity decay of slurry jets. Some integral properties were computed from numerical results such as entrainment and drag coefficients. The absolute entrainment coefficient was introduced and computational results indicated that slurry jets were more efficient in mixing than single-phase jets. From the computed values of drag coefficient, the grouping effect of particles was found to reduce the drag coefficient by half. Turbulent shear stresses of both sand-phase and water-phase were also estimated.