The translation of miscible jets and drops, and the dissolution of drops are common events encountered in numerous technological processes. It is critical to understand the evolution of the transient interfacial tension, which has eluded measurement. These challenges motivated methods recently demonstrated by the PIs groups to extract very small and transient interfacial tensions existing between miscible liquids. This collaborative research aims to develop a series of complementary experiments to understand the fluid dynamics of miscible pairs of liquids, which can interact with one another through various formats: miscible jets, miscible suspended droplets, and miscible sessile drops. These experiments will be supplemented by numerical simulations in collaboration with Professor Anderson of Eindhoven Technical University. Each of these multiphase flow systems result in outcomes that are qualitatively different from those encountered by immiscible liquid pairs. The specific aims are: (1) studies of drop and jets translating through a second, miscible liquid; (2) suspended droplets of a miscible liquid experiencing stagnation point extensional flow in a microfluidic environment; (3) sessile drops of a miscible liquid spreading and dissolving within a matrix liquid; and (4) diffuse interface simulation of miscible pendant drops, jets and sessile drops. The results from the modeling will be compared against experimental determinations of the interfacial shapes in jets and drops.
The dynamics of miscible liquid pairs has received little previous attention but are central to many physical processes. The combination of miscible materials can produce stable, intricate morphologies that are not possible with immiscible mixtures. Jets of miscible liquids can be used to great advantage in the scale-up production of highly oriented fibers that are otherwise difficult to process. The dissolution of miscible, sessile drops is a rich problem in multiphase flow that offers interesting analogies to desiccating drops along with the possibility of extracting measures of the interfacial tension between miscible liquids. The microfluidic approach to measuring interfacial tensions can be applied to other physical problems, such as systems undergoing chemical reactions, where the interfacial tension is changing with time. Similar approaches can also be adapted to incorporate different types of miscible fluids, drops, and biomolecules. The project will provide research training to graduate and undergraduate students. The results developed in this program will also make wonderful teaching tools for the introduction of fluid mechanics and interfacial phenomena to high school and undergraduate students.
