A CFD study is carried out to investigate the roles of neutrally buoyant particles in gas-liquid-solid flows in bubble columns. An Eulerian-Lagrangian model is used and the liquid flow is modeled using a volume-averaged system of governing equations, while motions of bubbles and particles are evaluated using Lagrangian trajectory analysis. Bubbles are assumed to remain spherical. Bubble-liquid interaction and particle-liquid interaction are included in the study. The drag, lift, buoyancy, and virtual mass forces are included in the discrete phase equations. Particle-particle interactions and bubble-bubble interactions are accounted for by a hard sphere model. The bubble coalescence is also included in the analysis. Neutrally buoyant particles are used in the study. The predicted results were compared with the experimental data in a previous work, and good agreement was obtained. The transient flow characteristics of a gas-liquid-solid three-phase flow and a gas-liquid two-phase flow are studied and the roles of neutrally buoyant particles are discussed. The simulations show that the transient characteristics of the flows in a bubble column are dominated by time-dependent vortices. The presence of particles can affect the characteristics of the flows and flows with particles evolve faster.

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