Coupled CFD-DEM simulation of fluids and bubbles in a stirring tank

The multiphase flow within a stirring tank predominantly exhibits complex turbulent motion, characterized by nonlinear and intricate interactions among different fluids. By treating the gas–liquid two-phase flow as a “fluid particle” system, we conducted numerical simulations of this flow in a stirring tank using a coupled computational fluid dynamics-discrete element method to investigate the movement dynamics of bubbles. A comparison between field test observations and simulation results reveals a close correlation between the two. The simulations were performed within Euler–Lagrange framework, taking interphase forces into account. The findings indicate that the water velocity in a stirring tank is primarily influenced by impeller speed, while water inflow has minimal impact on it. Notably, there is a significant decrease in water flow velocity upon encountering baffles. The dispersion patterns and movement speeds of bubbles are chiefly governed by water flow dynamics. Bubbles that remain in the stirring tank for extended periods tend to move predominantly above the tank’s surface, whereas their residence time in the lower and middle sections of the mixing tank is comparatively shorter. Furthermore, all bubbles exhibit fluctuating movement speeds ranging from 0.2 to 5 m/s.