Fluids: Jamming and Singular Flows

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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.