Topological mixing study of non-Newtonian duct flows

Tracer advection of non-Newtonian fluids in reoriented duct flows is investigated in terms of coherent structures in the web of tracer paths that determine transport properties geometrically. Reoriented duct flows are an idealisation of in-line mixers, encompassing many micro and industrial continuous mixers. The topology of the tracer dynamicsof reoriented duct flows is Hamiltonian. As the stretching per reorientation increases from zero, we show that thequalitative route from the integrable state to to global chaos and good mixing does not depend on fluid rheology.This is due to a universal symmetry of reoriented duct flows, which we derive, controlling the topology of the tracer web.Symmetry determines where in parameter space global chaos first occurs, while increasing non-Newtonian effects delays thequalitative value of the onset. Theory is demonstrated computationally for a representative duct flow, the rotated arcmixing flow