Euler-Euler Modeling of Poly-Dispersed Bubbly Flows

CFD simulations of bubbly flow on the scale of technical equipment become feasible within the Eulerian two-fluid framework of interpenetrating continua. For practical applications suitable closure relations are required which describe the interfacial exchange processes. To facilitate predictive simulations a reference set of closure relations has been defined for bubble forces and bubble-induced turbulence including numerical values for all parameters. Models for bubble coalescence and breakup are not yet included at present due to their lacking maturity. This means that the bubble size distribution must still be estimated by other means or treated as a parameter in a sensitivity study. Using measured bubbles sizes the validity of model predictions for gas fraction, mean velocities of gas and liquid, and liquid turbulent kinetic energy have been validated over a range of conditions. These include both pipe flows and bubble columns and circular and rectangular cross sections. The bubble size is limited to the range of 1 to 10 mm and the gas fraction to at most 10 to 20 %. The present report gives a brief but complete description of the model, a few validation examples, and references for further study.