Abstract:
Mixing processes play a fundamental role in numerous natural and industrial systems, impacting applications ranging from environmental fluid dynamics to chemical processing and pharmaceutical manufacturing. Mixing in yield-stress fluids is often assumed to be inefficient, but the underlying reasons remain poorly understood. In this talk, I explore how yield stress and fluid heterogeneity influence flow and shape mixing behavior. Using a combination of numerical simulations and physical insight, I show that even small variations in density or rheology can significantly impact mixing outcomes. I highlight three primary mixing mechanisms (interface stretching and folding, diffusion across streamlines, and dye advection) and demonstrate how the presence of a yield stress transforms these dynamics, leading to pronounced localization. These findings challenge conventional assumptions about mixing efficiency in complex fluids and suggest new strategies for analyzing and designing more effective stirring protocols in yield-stress materials.
