LES-based simulations for bubble columns: a comparative study based on turbulence models and interfacial forces

Bubble columns are systems of simple construction that are capable of providing adequate conditions for heat and mass transfer, being commonly used for biochemical processes such as microalgae cultivation or wastewater treatment. Their multiphase nature introduces a higher level of mathematical complexity during reactor design and optimization. The present work proposes a Computational Fluid Dynamics (CFD) procedure to predict the behavior of a bubble column reactor, using a large eddy simulation (LES) based model combined with a finite difference method (FDM) approach. The results obtained were compared with experimental and numerical data available in the literature for the air volume fractions distributions over different regions of the column and for the time-averaged gas holdup. A grid independence analysis resulted in a uniform mesh with low discretization errors. Different models for the estimation of the drag coefficient were considered, and the resulting profiles were compared with the experimental data. When compared to RANS-based models, the present FDM-LES model resulted in a significantly better agreement with experimental data, particularly for gas fraction profiles and average gas holdup in both the lower and upper regions of the column. This highlights the advantages of the LES approach.