Effects of settling particles on the bubble formation in a gas-liquid-solid flow system studied through a coupled numerical method

In this paper, the numerical investigation of the bubble formation and rise in gas-liquid-solid flow systems has been done through a coupled numerical method, the so-called volume of fluid (VOF) method, and a discrete element model (DEM). VOF is used to capture the interface of the bubble and DEM is employed to track the movement of particles. This coupled numerical method is validated through the good consistency of our calculated results to those experimental data (from other literature) of a bubble rising in a gas-liquid-solid system. The calculation results in this paper disclose that the detachment time of the first formed bubble is longer for case I (when particles are lying at the bottom of the container) than for case II (when the particles are settling freely). The main reason is that a stronger circulation (induced by the sedimentation of particles) near the bottom of the container plays a stronger cutting role and speeds up the detachment of the bubble. Then, the effects of some factors including particle volume fractions, gas velocities, orifice sizes, surface tensions, and liquid densities on the bubble formation and rise have also been investigated systematically. This work is useful for further research on the gas-liquid-solid fluidized bed system.