This study investigates the dynamics of a rising bubble in Newtonian and shear-thinning fluids under both stationary and rotating conditions using fully resolved direct numerical simulations. In stationary shear-thinning environments, the temporal evolution of rise velocity reveals a previously unreported negative drag regime, where the net hydrodynamic force assists upward motion, an effect absent in Newtonian cases. Despite similar trajectories, early-time velocity evolution remains indistinguishable between the two rheologies, highlighting a delay in the manifestation of non-Newtonian effects. Under rotation, centrifugal and Coriolis forces compete with buoyancy to reverse the bubble's ascent. While Newtonian bubbles exhibit earlier deflection, shear-thinning fluids show enhanced trajectory stability due to rheology-induced damping. Finally, this work develops a novel closed-form predictive model, based on force balance, that accurately estimates the critical time of reversal across a range of Rossby numbers. These results offer new physical insights and a reduced-order framework for bubble dynamics in complex multiphase systems.
Sahu et al. (Fri,) studied this question.