Numerical simulations on gas-liquid-particle three-phase flows under microgravity

Three-phase gas-liquid-particle flows under microgravity condition were numerically studied. An Eulerian-Lagrangian computational model was used in the simulations. In this approach, the liquid flow was modeled by a volume-averaged system of governing equations, whereas motions of particles and bubbles were evaluated using the Lagrangian trajectory analysis procedure. It was assumed that bubble shape variations were neglected and the bubbles remained spherical. The bubble-liquid, particle-liquid and bubble-particle interactions were accounted for in the analysis. The discrete phase equations included drag, lift, buoyancy, and virtual mass forces. Particle-particle interactions and bubble-bubble interactions were accounted for by the hard sphere model. Bubble coalescence was also included in the model. The transient flow characteristics of the three-phase flow were studied. The effects of gravity and g-jitter acceleration on variation of flow characteristics were discussed. The low gravity simulations showed that most bubbles are aggregated in the inlet region and the bubble plume exhibits a plug type flow behavior. The particles are mainly located outside the bubble plume, with very few particles being retained in the plume. Compared to the normal gravity condition, the three phases in the column are poorly mixed under microgravity conditions. The velocities of the three phases were also found to be of the same order. The simulation results showed that the effect of g-jitter acceleration on the gas-liquid-particle three phase flows is small.