(270c) Mixing and Shear-Induced Migration in a 2D Time-Periodic Cavity-Driven Flow

This study investigates mixing and segregation resulting from the competition between shear-migration and chaotic advection. In colloidal suspensions, particles do not behave as passive tracers. Local fluid deformation can result in cross-streamline migration due to the multi-body hydrodynamic interactions of particles, leading to concentration inhomogeneity. This behavior is studied numerically in a rectangular cavity flow with alternating periodic driving forces at top and bottom walls, a prototypical system for studying 2D chaotic advection (Ottino 1989). The combination of chaotic advection, repeatedly stretching and folding fluid elements, and diffusion enhance dispersion. Mixing and segregation, measured by the intensity of segregation, as a result of this interplay between shear-demixing and chaotic advection is highly complex. The effects from factors such as average volume fraction, particle radius, driving force and period are explored and compared to the underlying flow topology, as characterized by Poincaré maps.