• Benjamin bubble
• high-viscosity fluids
• multiphase flow
• open-source CFD code
• slug flow

In this work the capabilities of an open-source CFD code (OpenFOAM) in the simulation of the Benjamin bubble are benchmarked against the available experimental data, theoretical analysis and numerical results of simulations carried out with a commercial code. The simulations are carried out for a large range of Reynolds numbers, obtained by using both water and high-viscosity oils. The volume of fluid (VOF) multiphase model is used in the simulation. The dynamics of the Benjamin bubble is investigated in terms of bubble drift velocity and shape. The sensitivity of the results to the size of the time step, to the numerical discretization schemes and to grid refinement and topology is investigated by using water as working liquid. It is found that the most critical parameters are grid topology and resolution. The results obtained on a structured hexaedral grid of adequate resolution show good agreement with experimental data both in terms of bubble shape and drift velocity. In particular, the bubble shape obtained with OpenFOAM is closer to the experimental one than that found in analogous simulations carried out with a commercial code.