Characterization of Coherent Structures from Parallel, L.E.S. Computations of Wandering Effects in Bubble Plumes

This paper is aimed at characterizing turbulence in bubble plumes undergoing a transient motion, a topic of primary importance in many environmental applications. Mathematical models for dilute mixtures, derived from the two-fluid model equations (multiphase flow theory), are initially presented. These models include diverse degrees of complexity, and they handle turbulence via a k - ε model and a Large-Eddy Simulation (LES) approach, in a consistent way. The models are implemented in a parallel code, which is then used to numerically simulate the dynamic behavior of bubble columns in three dimensions, using the LES approach. The results of high-resolution simulations show the presence of coherent structures whose distributions in space, and number, change with time. These structures are characterized in the paper via several indicators, connecting them with potential events of breakup of bubbles.