Discrete phase simulation of gas–liquid–solid fluidization systems: single bubble rising behavior

Abstract

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 study. In this scheme, the volume-averaged method, the dispersed particle method, and the volume-of-fluid (VOF) method are used to account for the flow of liquid, solid particles, and gas bubbles respectively. The gas–liquid interfacial mass, momentum and energy transfer is described by a continuum surface force (CSF) model. A close-distance interaction (CDI) model is introduced 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 equation of motion of particles. The particle–liquid interaction is brought into the liquid phase Navier–Stokes (N–S) equations through the use of Newton's third law of motion. The volume-averaged liquid phase N–S equations are solved using the time-split two-step projection method. The simulation results using this scheme are verified for bed expansion and pressure drop in liquid–solid fluidized beds. The simulation of a single bubble rising in a liquid–solid suspension and the particle entrainment by a bubble on the surface of the bed is conducted and the results are in agreement with the experimental findings.