RUI: Lagrangian Chaos: Phase Separation, Coalescence and Aggregation

这个凝聚态物理项目集中于拉格朗日混沌（混沌粒子运动和流体混合）对多相过程的影响：相分离和聚并；液滴破碎，悬浮粒子聚集。从基础和实践的角度来看，人们对这些过程都很感兴趣。以往的研究主要是研究简单剪切流对多相过程的影响；然而，这些研究没有考虑不同切变区域之间液滴的平流。平流尤其重要，因为最近发现拉格朗日混沌发生在本身不是混沌或湍流的流动中；相反，即使在有序的层流中也会出现混沌轨迹。这项研究将推广以前用于表征多相过程的测量方法（例如，毛细数），以解释一般的平流，特别是拉格朗日混沌。提出了一系列由交替涡链组成的简单二维和三维流体流动的实验和数值模拟。这些研究完全是在本科生中进行的；这项研究为他们在必须做出重要职业决定的时候提供了一个体验新奇研究的机会。此外，他们学到的技巧有助于他们为研究生院和/或学术界、工业界或政府的职业生涯做好准备。拉格朗日混沌是流体流动中的杂质可以沿着混沌轨迹运动的过程，即使流动本身是非常简单和有序的。提出了实验来研究拉格朗日混沌对多相过程的影响，多相过程涉及含有第二种不混相流体（如水中的油）或悬浮颗粒的流体。研究将在二维和三维流动中进行，并将通过数值模拟来补充实验。该研究适用于广泛的工业过程，因为许多应用都采用多相流体系统。以前的研究集中在简单的剪切流如何将不混溶的流体分解成更小的液滴或阻止它们聚集成更大的液滴。然而，这些研究没有考虑不同剪切区域之间液滴的混沌运动。本研究将填补这一认识上的空白。这些研究完全是在本科生中进行的；在他们必须做出重要的职业决定时，这项研究为他们提供了体验新奇研究的机会。此外，他们学到的技巧有助于他们为读研和/或在学术界、工业界或政府工作做好准备

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.***