Numerical Studies of Multi-Bubble Formation Dynamics in Gas-Liquid-Solid Fluidization Systems at High Pressures

摘要

A discrete phase simulation is conducted to investigate multi-bubble formation dynamics in gas-liquid-solid fluidization systems. A numerical technique based on computational fluid dynamics (CFD) with the discrete particle method (DPM) and volume tracking represented by the volume-of-fluid (VOF) method is developed and employed for the simulation. A bubble induced force model, a continuum surface force model, and Newton's third law are applied to account for the couplings of particle-bubble, bubble-liquid and particle-liquid interactions, respectively. A close-distance interactive effect between colliding particles is considered in the formulation of the particle-particle collision model. Two-dimensional simulations fo the process of multi-bubble formation from multi-orifices in liquids and liqui-solid suspensions are conducted at high pressures up to 19.4 MPa under constant flow conditions. Experiments are also conducted in this study to quantify the bubble formation hehavior from a single oifice under comparable gas flow conditions. The study indicates that there is a significant effect of bubble and bubble wake induced liquid flow dynamics, which significantly affect the bubble formation process. The simulation results on iniitial bubble size and bubble formation time under various pressures are found to be in good agreement with those obtained experimentally as well as those predicted based on the analytical model developed earlier by the authors.