Modelling and Simulation of Gas-Liquid Hydrodynamics in Mechanically Stirred Tanks

Computational fuid dynamics (CFD) is an increasingly important tool for carrying out realistic simulations of process equipment. In the case of multiphase systems the development of CFD models is less advanced than for single-phase systems. In the present work CFD simulations of gas-liquid stirred tanks are reported. An Eulerian-Eulerian multi-fluid approach is used in conjunction with the simplest two-phase extension of the k-ɛ turbulence model. All bubbles are assumed to share the same size. The effect of inter-phase forces on simulation results is separately considered. As concerns drag, it is shown that the sole parameter needed to characterize the dispersed phase behaviour is bubble terminal velocity, a consideration that eases the estimation of the relevant term in the momentum equations and helps understanding the system physics. Despite the many simplifications adopted, results are found to be in satisfactory agreement with experiment.