In this paper, the flow instabilities during the rise of a single bubble in a narrow vertical tube are studied using a transient 2D/axisymmetric model. These instabilities include the oscillation of the bubble shape and formation of a wake behind it. In the model, 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 liquid/gas interface. The numerical results are validated by a comparison with available measurements. The effect of different parameters such as tube and bubble diameters, and liquid properties are investigated.

Keywords