Evaluation of models for bubble-induced turbulence by DNS and utilization in two-fluid model computations of an industrial pilot-scale bubble column

Abstract

This paper presents numerical studies on modeling of bubble induced turbulence at two significantly different scales. On the scale of a bubble swarm, direct numerical simulations are performed with a geometric volume-of-fluid method and the budget equation of liquid phase turbulence kinetic energy is analyzed. By a priori testing of models for the interfacial term in this equation, suitable closure relations are identified. On the scale of an industrial bubble column, simulations with a two-fluid model are performed with water and cumene as liquid phases under elevated pressures. Turbulence is taken into account by a mixture k–ε model, considering two closure relations for the interfacial term identified from the DNS. For both liquids, an influence of the model for the interfacial term on turbulence kinetic energy and gas holdup is found, which is, however, small at elevated pressures. Numerical results for local and overall gas holdup are in reasonable agreement with measurements reported for this industrial pilot-scale bubble column. For the overall gas holdup, an empirical correlation from literature is identified which predicts the present numerical results reasonably well.