Influence of Initial Separation and Alignment on the Interaction of Rising Bubbles in Viscous Solutions

The ascending movement of bubbles in different viscous solutions was studied in this work using the volume of fluid (VOF) method. The behavior of two ascending bubbles was investigated for different initial conditions. So, we analyzed the influence of the dimensionless initial separation distance, S*0, and the initial acute angle, θ0, on the bubble-bubble and bubble-liquid interaction. It is observed that bubble trajectories are mainly influenced by the oscillations of their shapes and the wake structure behind them. In the case of one bubble, for low Eötvös (Eo) and low Galilee (Ga) numbers, the bubble keeps azimuthal symmetry. However, at low Eo and high Ga, the bubble begins to display a zigzag motion, and its shape changes over time. For two identical bubbles, we found that the distance between their centers, as well as their initial configuration (horizontal or oblique initial bubble alignment), has a considerable influence on their interaction: (i) coalescence, (ii) bouncing without coalescence, (iii) separation between the two bubbles.