| Fluid mixing is a complex process consisting of a variety of physical mechanisms. This work focuses on the role of fluid motion in mixing. Unlike many fluid mechanical studies in which the velocity field constitutes the solution to the problem, analysis of mixing actually commences with specification of the velocity field. In order for the mixing to be effective, the fluid motion must be chaotic.; Mixing is investigated in four systems: the eggbeater flow, the cavity flow, the partitioned-pipe mixer (PPM), and the eccentric helical annular mixer (EHAM). All the flows exhibit chaos because they contain the mechanisms of stretching of fluid along streamlines and reorientation of fluid across streamlines.; The eggbeater and cavity flows are two-dimensional flows which exhibit chaos due to their time dependence. Although it cannot be realized experimentally, the eggbeater flow exhibits many characteristics displayed in more complex flows. It is easily analyzable, and is used to introduce techniques used for study of more complex systems. The cavity flow is an experimentally realizable flow with no analytic expressions for the motion or the velocity field. However, the flow can be analyzed in terms of symmetries. Emphasis is on enhancement of mixing by deduction and manipulation of symmetries in the flow.; The PPM and EHAM are prototypes of a class three-dimensional continuous flows comprised of a two-dimensional cross-sectional motion augmented by a unidirectional axial flow, referred to as duct flows. Unlike two-dimensional flows, chaos can be induced in duct flows by altering the cross-sectional flow either in time, as in the EHAM, or space, as in the PPM. Mixing is compared in these two flows, utilizing techniques from two-dimensional flows, as well as techniques unique to duct flows. Similarities and differences between mixing in two- and three-dimensional flows are discussed. |
