Numerical investigation of particle cloud sedimentation in power-law shear-thinning fluids for moderate Reynolds number

Abstract

A series of numerical simulations are performed for the sedimentation process of a particle cloud in shear-thinning fluids using lattice Boltzmann and discrete element methods. The initial particle concentration, c0, and the power-law index of the fluid, n, and Reynolds number, Re, are varied in these simulations. For 1.0⩽Re⩽10.9, the particle cloud size grows in the longitudinal direction as the cloud settles, leading to reduced particle concentration and a quasi-steady settling velocity, w¯∞. The velocity ratio, w¯∞/w∞, where w∞ is the corresponding single-particle terminal velocity, is found to decrease with both n and Re. This velocity ratio is only weakly dependent on the initial concentration (0.05⩽c0⩽0.20) due to particle dispersion. For 0.071⩽Re<1.0, the cloud loses its initial shape and disintegrates while settling, with particles escaping from the cloud due to differential particle settling velocities.