Discrete phase simulation of bubble and particle dynamics in gas-liquid-solid fluidization systems

The dynamic behavior of the collision of two elastic spheres is studied in stagnant viscous fluids for particle Reynolds numbers ranging from 5 to 300. The interactive behavior of these particles is examined both experimentally and theoretically. The lattice-Boltzmann (LB) simulation is conducted to obtain the detailed three-dimensional flow field and the forces around the particles during the course of collision. Furthermore, a mechanistic model is developed which accounts for four stages of collision processes. The LB simulation and experimental results lead to an empirical expression for the drag force on the particle during the close-range particle-particle interaction.; A computational scheme for discrete-phase simulation of a gas-liquid-solid fluidization system and a two-dimensional code based on it are developed. In this scheme, the volume-averaged method, the dispersed particle method, and the volume-of-fluid (VOF) method are used for simulating the flow of liquid, solid particles, and gas bubbles, respectively. The close-distance interaction model is included which illustrates the motion of the particle prior to its collision; upon collision, the hard sphere model is employed. The particle-bubble interaction is formulated by incorporating the surface tension force in the particle motion equation. The particle-liquid interaction is brought into the liquid phase Navier-Stokes equations through the use of the Newton's third law of motion.; The simulation results using this scheme are verified for bed expansion and pressure drop in liquid-solid fluidized beds. Simulations of a single bubble rising in a liquid-solid suspension and the particle entrainment in the freeboard by an emerging bubble are also in agreement with the experimental data. Numerical studies are performed on the bubble and particle dynamics in bubble columns and three-phase fluidized beds at high pressures. Simultaneous simulations for both liquid and gas phases are performed with a volume fraction weighted averaged method to calculate the properties on the interface. The wake interactions and the bubble coalescence and breakup are also simulated and agree with the experimental observations. The effects of pressure and solids holdup on the bubble rise characteristics such as the bubble rise velocity, bubble shape and trajectory are examined. The simulation results of particle-bubble interactions and the maximum stable bubble size agree well with the experimental data.