Evolutionary analysis of typical characteristics for a single bubble rising in shear-thinning viscoelastic liquids

To elucidate the dynamics of a single bubble rising through shear-thinning viscoelastic liquids, the evolution of characteristic parameters against time was analyzed. The bubble interface was tracked using the volume of fluid (VOF) method, the liquid’s shear-thinning behavior was characterized using the Carreau model, and the viscoelasticity was characterized using the FENE-CR model. Detailed analyses were conducted on bubble shape, liquid-phase velocity, static pressure, viscous stress, and elastic stress fields in representative scenarios. The results reveal that while the elastic stress in the liquid generally increases over time, the viscous stress is significantly influenced by a negative wake, showing complex variations. The hysteresis of elastic stress indicates that bubble deformation in viscoelastic liquids occurs in two distinct phases: initially dominated by viscous stress, surface tension, and pressure, followed by a phase where elastic stress becomes the primary influence. When the shear-thinning effect is pronounced (n = 0.2) and the surface tension is relatively weak (Eo = 100), a single bubble tends to deform into a cap-like shape with a tip. The interplay between elastic and viscous stresses at the bubble’s tail leads to a negative wake, and the bubble’s periodic deformation correlates with the ratio of the polymer relaxation time to the bubble motion time.