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Chemical Engineering Science, Vol.56, No.4, 1737-1747, 2001
Modelling and simulation of the dynamic flow behaviour in a bubble column
A three-dimensional dynamic Eulerian-Eulerian two-phase model is used for the modelling of bubble column hydrodynamics in the homogeneous flow regime. The turbulence in liquid phase is considered by the standard k-epsilon model. Further numerical studies investigate the influence of additional turbulence production through the dispersed gas phase. The dispersed phase is represented 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 predict both the time-averaged and the dynamic flow behaviour. The measured low-frequency velocity fluctuations are used for the validation of the simulated large-scale flow dynamics that is dominated by the irregular movements of the bubble plume and the vortical structures in the liquid phase. The consideration of bubble-induced turbulence shows positive as well as negative impacts on the quality of the simulation results for a coarse numerical grid. Due to the mutual influences, the turbulence model has to be discussed together with the grid resolution. Employing finer grids improves the description of the vortical flow structure in the bubble column and the agreement with the experimental data. However. the computation power increases significantly and a compromise between efficiency and quality of results has to be found.