CFD simulation of gas-liquid stirred vessels

Computational Fluid Dynamics is an increasingly important tool for carrying out realistic simulations of process apparatuses. As a difference from single phase systems, for multipliase systcms the development of CFD models is still at its early stages. In the present work CFD simulations of gasliquid stirred tanks are reported. All bubbles are assumed to share the same size, and a simplified approach is adopted for the description of momentum exchanges between tile two phases. In particular ir is shown that the only parameter needed for modeling drag forces is bubble terminal velocity. Results show that in a quite wide range encompassing most practical applications, bubble size has a limited effect on flow fields as well as on total gas hold-up and ia distribution in the vessel space. This result implies that coalescencelbreakage dynamics computations may be conveniently carried out off-line after having assessed the vessel flow field, with large savings of co~nputational demand.