Euler-Euler large eddy simulations of the gas-liquid flow in a cylindrical bubble column

In this work Euler-Euler Large Eddy Simulations (LES) of dispersed turbulent gas-liquid flows in a cylindrical bubble column are presented. Besides, predictions are compared with experimental data from Vial et al. 2000 using laser Doppler velocimetry (LDV). Two test cases are considered where vortical-spiral and turbulent flow regimes occur. The sub-grid scale (SGS) modelling is based on the Smagorinsky kernel with model constant C-s = 0.08 and the one-equation model for SGS kinetic energy. The emphasis of this work is to analyse the performance of the one-equation SGS model for the prediction of bubbly flow in a three-dimensional high aspect ratio bubble column (H/D) of 20 and investigate the influence of the superficial gas velocity using the OpenFOAM package. The model is compared with the Smagorinsky SGS model and the mixture k - epsilon model in terms of the axial liquid velocity, the gas hold-up and liquid velocity fluctuations. The bubble induced turbulence and various interfacial forces including the drag, virtual mass and turbulent dispersion where incorporated in the current model. Overall, the predictions of the liquid velocities are in good agreement with experimental measurement using the one-equation SGS model and the Smagorinsky model which improve the mixture k model in the core and near-wall regions. However, small discrepancies in the gas hold-up are observed in the bubble plume region and the mixture k model performs much better. The numerical simulations confirm that the energy spectra of the resolved liquid velocities in churn-turbulent regime follows the classical -5/3 law for low frequency regions and are close to -3 for high frequencies. More details of the instantaneous local flow structure have been obtained by the Euler-Euler LES model including large-scale structures and vortices developed in the bubble plume edge.