Centrifugal creaming dynamics in dense shear-thinning emulsions

Centrifugal creaming of non-Newtonian continuous-phase dense emulsions results from a complex interplay between droplet-scale hydrodynamics, shear-dependent viscosity, and concentration-driven hindrance. Despite extensive work on Newtonian systems, physically consistent modeling frameworks for shear-thinning continuous-phase emulsions remain limited. In the present study, we combine space- and time-resolved analytical centrifugation, a one-dimensional convection–diffusion model, and Euler–Euler computational fluid dynamics (CFD) simulations to examine the effects of droplet size, dispersed-phase fraction, and polymer-induced rheology of the continuous phase on creaming dynamics. As expected, experiments using carboxymethylcellulose- and xanthan-thickened emulsions show that creaming velocity decreases with increasing the continuous-phase viscosity, shear-thinning intensity, and dispersed-phase fraction, while larger droplets migrate faster. The extended convection–diffusion model incorporates power-law rheology, polydispersity in the drop size, and hydrodynamic hindrance due to higher dispersed-phase fractions. Among the velocity formulations tested, the Kumar–Hartland model consistently provides the closest agreement with the experimental trends under the different tested conditions. CFD simulations provided local velocity and revealed stress gradients, the formation of compacted layers, and viscosity heterogeneities that corroborate the one-dimensional model predictions. Overall, the combined experimental and modeling approach provides a physically consistent and calibrated framework for analyzing phase separation dynamics in shear-thinning dense emulsions under centrifugal or gravitational fields.