RUI: Lagrangian Chaos: Phase Separation, Coalescence and Aggregation

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This condensed matter physics project concentrates on the effects of Lagrangian chaos (chaotic particle motion and fluid mixing) on multiphase processes: phase separation and coalescence; droplet break-up, and aggregation of suspended particles. There is significant interest in these processes, both from fundamental and practical perspectives. Previous research has studied the effects of simple shearing flows on multiphase processes; however, those studies did not consider advection of drops between regions with varying shear. Advection is particularly important in light of recent discoveries that Lagrangian chaos occurs for flows that are not chaotic or turbulent themselves; rather, chaotic trajectories occur even in well-ordered, laminar flows. This research will generalize previous measures used to characterize multiphase processes (e.g., the Capillary number) to account for advection in general and Lagrangian chaos in particular. A series of experiments and numerical simulations are proposed in simple two- and three-dimensional fluid flows composed of chains of alternating vortices. The studies are done entirely with undergraduates; the research provides them with an opportunity to experience novel research at a time when they must make important career decisions. Furthermore, the techniques that they learn help prepare them for graduate school and/or careers in academics, industry or government.%%%Lagrangian chaos is the process by which impurities in a fluid flow can follow trajectories that are chaotic, even if the flow itself is very simple and well-ordered. Experiments are proposed to study the effects of Lagrangian chaos on multiphase processes, which involve fluids containing either a second, immiscible fluid (such as oil in water) or suspended particles. Studies will be done in both two- and three-dimensional flows, and the experiments will be complemented by numerical simulations. The research is applicable to a wide range of industrial processes, since many applications employ multiphase fluid systems. Previous research focused on how simple shearing flows break up immiscible fluids into smaller droplets or prevent them from coalescing into larger drops. However, those studies did not consider chaotic motion of drops between regions of varying shear. The proposed research will fill the gap in this understanding. The studies are done entirely with undergraduates; the research provides them with opportunities to experience novel research at a time when they must make important career decisions. F Furthermore, the techniques that they learn help prepare them for graduate school and/or careers in academics, industry or government.***