Fluids: Jamming and Singular Flows

本项目研究：(1)过冷液体和玻璃；(2)流体界面中出现的奇点。这项工作的动机是，不同的材料在被卡住或变硬的方式之间可能存在潜在的相似性。这项工作研究了从玻璃化转变为具有屈服应力的无定形固体的液体与宏观的、无热的系统之间的相似性，例如颗粒状材料，它被挤进一个构型中，也具有屈服应力。通过对液体的模拟和实验，我们将探索一种“干扰相图”，将这两种看似不相交的转变结合起来，看看降低温度产生的干扰是否与降低应力产生的干扰相似。还将对力链的形成进行调查。液体表面奇点将通过高速摄影来探测，以检查当液滴分裂成两个独立的碎片时界面上发生的奇点。喷口形成本身将使用选择性抽吸的几何形状进行研究。将探索涂层颗粒的可能应用。参与这项研究的学生将在高度跨学科的科学课题上接受出色的训练，使用新颖的仪器和测量方法。许多不同的材料被卡住而不能移动。在工厂的管道和漏斗中流动的颗粒状物料中可以观察到这种堵塞。当分子液体被冻结成无定形时，也可以在玻璃形成的背景下看到它。这项研究旨在探索这两种看似不同类型的转变实际上可能与相似的潜在物理机制相互关联的方式，从而导致运动停止。这种根本原因的发现将对各种科学和技术问题产生重要影响。计算机模拟和实验将用于探索这些干扰过渡。当一滴液体从一个较大的流体体中分离出来时，流体流动中的奇点是很重要的。在这种情况下，由于气流的奇异性，对物体的简单数学描述就失效了。高速摄影研究将探索这些奇点的本质。还将研究使用选择性退出的几何形状的喷嘴形成。将探索这种现象用于涂层颗粒，包括用于医疗应用的细胞。参与这项研究的学生将在高度跨学科的科学课题上接受出色的训练，使用新颖的仪器和测量方法。

This project investigates : (1) supercooled liquids and glasses and (2) singularities appearing in fluid interfaces. The work is motivated by the possibility of an underlying similarity between the ways in which different materials can become jammed, or rigid. This work studies similarities between a liquid undergoing a glass transition into an amorphous solid, with a yield stress, and a macroscopic, athermal, system, such a granular material, which becomes jammed into a configuration, also with a yield stress. A "jamming phase diagram", which unifies these two seemingly disjoint transitions, will be explored using simulations and experiments on liquids to see if jamming produced by lowering temperature is similar to jamming produced by lowering the stress. There will also be an investigation of force-chain formation. Liquid surface singularities will be probed via high-speed photography to examine the singularity in the interface occurring when a drop splits into two separate pieces. The spout formation itself will be studied using the geometry of selective withdrawal. Possible applications for coating particles will be explored. The students involved in this research will receive excellent training with novel instruments and measurements on highly interdisciplinary scientific topics. %%%Many different materials become jammed so that they cannot move. Such jamming can be observed in granular material flowing through conduits and hoppers in a factory. It can also be seen in the context of glass formation when a molecular liquid is frozen into an amorphous state. This research is aimed at exploring the ways in which these two seemingly disparate types of transitions may in fact be related to each other with similar underlying physical mechanisms at work to cause the cessation of motion. The discovery of such an underlying cause would have important implications for a variety of scientific and technological problems. Both computer simulations and experiments will be used to explore these jamming transitions. Singularities in fluid flow are important whenever a drop of liquid breaks off from a larger body of fluid. At such a point a simple mathematical description of the object breaks down because of the singular nature of the flows. High-speed photographic studies will probe the nature such singularities. There will also be a study of the spout formation using the geometry of selective withdrawal. The use of this phenomenon for coating particles, including cells for medical applications, will be explored. The students involved in this research will receive excellent training with novel instruments and measurements on highly interdisciplinary scientific topics.