Euler/Lagrange Calculations of Bubbly Flows with Consideration of Bubble Coalescence

A bubble coalescence model was developed on the basis of the Lagrangian approach, where bubbles are followed through the turbulent flow field along their trajectories. The collision process was described using a stochastic inter-particle collision model. Coalescence occurred if the contact time became larger than the film drainage time. The film drainage time was determined by a simple formulation according to classical approaches, whereas the contact time resulted directly from the collision model. The performance of the model was analyzed for bubble rise in a prescribed homogeneous isotropic turbulence field. Moreover, numerical calculations by the coupled Euler/Lagrange approach were performed and compared with measurements in a bubble driven loop facility. The comparison showed reasonably good agreement for liquid and bubble velocities.