Deformation and Aspect Ratio of Bubbles Continuously Rising in Shear-Thinning Fluids

The shape deformation of three bubbles with equilateral triangle arrangement continuously rising in shear-thinning non-Newtonian fluids was numerically investigated using the three-dimensional volume of fluid method (3D-VOF). The shape deformation of three continuously rising bubbles was compared with that of a single bubble under consistent operations to analyze the effect of interaction between bubbles. The influences of bubble diameter, initial bubble distance, bubble formation frequency, and liquid rheological property on the aspect ratio of the bubble were investigated. The results indicate that the aspect ratio of the bubble for multi-bubble systems with greater bubble diameter, initial bubble distance, and more intense shear-thinning effect of the liquid decreases, and the shape of the bubble deforms flatter. However, as the bubble formation frequency increases, the deformation of the bubble weakens, and the bubble aspect ratio increases. In comparison with the single bubble rising freely, the aspect ratio of the bubble for the multi-bubble systems is larger. Moreover, a modified model of the aspect ratio of the bubble was proposed by considering the interaction between bubbles for the multi-bubble system.