RUI: Granular Dynamics, and Fluid Mixing in Complex Flows

本项目将研究颗粒状材料和流体所表现出的非线性现象。该项目采用小型实验室实验，由本科生进行，他们是研究的全面合作伙伴。这项工作有两个主要的重点：(1)研究剪切和振动系统中的颗粒动力学，使用灵敏的力测量和快速的颗粒跟踪。这项工作将揭示宏观流动特性如何依赖于材料的内部结构。将强调多分散性（粒度的变化）的作用，包括抑制有序和剪切引起的偏析。其他实验将探索粒子运动的统计，慢动力学和存在应力时的滑移，以及由于缺乏反射对称的手性粒子引起的集体旋转等新效应；(2)流体流动中拉伸的高分辨率测量方法将扩展到弱湍流、小型装置中非牛顿流体的混合以及简单化学反应中的平流等重要问题。与该项目相关的研究生和博士后研究人员学习指导本科生，并通常在本科院校担任教职。这个项目将探索颗粒材料和流体所表现出的所谓“非线性现象”。该项目采用小型实验室实验，由本科生进行，他们是研究的全面合作伙伴。这项工作有两个主要重点：(1)对剪切和振动颗粒材料的研究将有助于更好地理解涉及小颗粒的工业和自然现象。实验将揭示宏观流动特性如何取决于材料的内部结构，以及颗粒大小的变化如何影响结构和流动。其他实验将探索在有应力的情况下缓慢蠕变，以及粒子缺乏镜像对称性时发生的集体旋转；(2)拉伸是许多流体流动中的一个重要现象，该程序开发的方法首次允许对其进行定量测量。拉伸将用于(a)表征和控制复杂流体的混合，如对未来技术至关重要的小型设备中的聚合物溶液，(b)研究弱湍流，(c)研究流动在化学反应中的作用。与该项目相关的研究生和博士后研究人员学习指导本科生，并通常在本科院校担任教职。

This project will investigate nonlinear phenomena exhibited by granular materials and fluids. The project employs small-scale laboratory experiments that are carried out by undergraduate students, who are full partners in the research. There are two main foci for this work: (1) Studies of granular dynamics in sheared and vibrating systems, using sensitive force measurements and rapid particle tracking. This work will reveal how the macroscopic flow properties depend on the internal structure of the material. The role of polydispersity (variations in particle size) will be emphasized, including the suppression of ordering, and segregation induced by shear. Other experiments will explore the statistics of particle motion, slow dynamics and slip in the presence of stress, and novel effects such as collective rotation due to chiral particles lacking reflection symmetry; (2) Methods for highly resolved measurements of stretching in fluid flows will be extended to the important problems of weak turbulence, mixing of non-Newtonian fluids in small devices, and advection in simple chemical reactions. Graduate student and postdoctoral researchers associated with this program learn to mentor undergraduates, and typically assume faculty positions in undergraduate institutions. This project will explore so-called "nonlinear phenomena" exhibited by granular materials and fluids. The project employs small-scale laboratory experiments that are carried out by undergraduate students, who are full partners in the research. There are two main foci for this work: (1) Investigations of sheared and vibrating granular materials will lead to a better understanding of industrial and natural phenomena involving small particles. The experiments will reveal how the macroscopic flow properties depend on the internal structure of the material, and how variations in particle size affect both structure and flow. Other experiments will explore slow creep in the presence of stress, and collective rotation that occurs when particles lack mirror symmetry; (2) Stretching is an important phenomenon in many fluid flows, and methods developed in this program allow its quantitative measurement for the first time. Stretching will be used (a) to characterize and control the mixing of complex fluids such as polymer solutions in small devices that are critical to future technologies, (b) to study weak turbulence, and (c) to investigate the role of flow in chemical reactions. Graduate and postdoctoral researchers associated with this program learn to mentor undergraduates, and typically assume faculty positions in undergraduate institutions.