In this paper, the rising of a single bubble in a viscous liquid and its departure from the free-surface are simulated using a transient 2D/axisymmetric model. To predict the shape of the bubble deformation, the Navier-Stokes equations in addition to an advection equation for liquid volume fraction are solved. A modified Volume-of-Fluid (VOF) technique based on Youngs’ algorithm is used to track the bubble deformation. To validate the model, the results of simulations for terminal rise velocity and bubble shape are compared with those of the experiments. Next, the effect of different parameters such as initial bubble radius, channel height, and liquid viscosity and surface tension on the shape and rise velocity of the bubble is investigated. Finally, the interaction of the bubble with the free surface during its departure from the liquid is simulated, and the results are compared qualitatively with experimental photographs.

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