Modelling and simulation of the dynamic flow behaviour in a bubble column

A three-dimensional dynamic Eulerian-Eulerian two-phase model is used for t he modelling of bubble column hydrodynamics in the homogeneous flow regime. The turbulence in liquid phase is considered by the standard k-epsilon mod el. Further numerical studies investigate the influence of additional turbu lence production through the dispersed gas phase. The dispersed phase is re presented by a mono-dispersal neglecting coalescence and break up effects. Detailed experiments performed in a cylindrical bubble column allow for the validation of the model. The measurements focus on the local liquid-phase velocities and gas void fractions. The numerical simulations successfully p redict both the time-averaged and the dynamic flow behaviour. The measured low-frequency velocity fluctuations are used for the validation of the simu lated large-scale flow dynamics that is dominated by the irregular movement s of the bubble plume and the vortical structures in the liquid phase. The consideration of bubble-induced turbulence shows positive as well as negati ve impacts on the quality of the simulation results for a coarse numerical grid. Due to the mutual influences, the turbulence model has to be discusse d together with the grid resolution. Employing finer grids improves the des cription of the vortical flow structure in the bubble column and the agreem ent with the experimental data. However. the computation power increases si gnificantly and a compromise between efficiency and quality of results has to be found. (C) 2001 Elsevier Science Ltd. All rights reserved.