Numerical Simulation of a Rising Bubble in a Shear-Thinning Fluid under Pressure-Oscillating Field

Abstract

When pressure-oscillation is applied to a highly viscous solution containing a bubble, the bubble rising velocity is significantly enhanced compared to its natural bubble rising velocity. In this study, unsteady-state non-Newtonian finite element analysis is performed, in which the shape of the air-liquid interface can be determined by the force balance equation, considering inertia and the gravitational term. It was found that the alternative local flows near the bubble surface generated by pressure-oscillation give rise to lowered apparent viscosity for shear-thinning fluid, and enhancing the bubble rising velocity, as well. In addition, it was also found that the bubble rising velocity during contraction phase is faster than that during the expansion phase.