Inertial migration of spherical particles in channel flow of power law fluids

Abstract

The cross-stream inertial migration of neutrally buoyant particles in a power law fluid in a pressure-driven flow between two parallel walls is studied using three-dimensional numerical simulations. The particles are modeled as rigid and compliant spherical shells filled with a Newtonian fluid. Our simulations show that the particles in the flow equilibrate at stable off-center positions that depend on the particle size and fluid power exponent. In a shear thickening fluid, the equilibrium position is insensitive to the particle size. In a shear thinning fluid, an additional unstable off-center equilibrium position emerges for smaller particles, which leads to the accumulation of such particles at the channel centerline. We find that these equilibrium positions are insensitive to the magnitude of the channel Reynolds number and particle elasticity. The results of our study have applications to sorting, focusing, and separation of synthetic particles and biological cells.