(276c) Using Mri Techniques to Study Hydrodynamic Forces in the Coalescence of Emulsions

An emulsion is a thermodynamically unstable mixture of two immiscible fluids with one fluid being dispersed in the other. Coalescence, which is the fusion of two similarly sized drops forming a larger drop, is one of several emulsion breakdown methods. The coalescence mechanism can be broken into four distinct steps: Collision, Film Drainage, Film Rupture, and Confluence. These four steps happen sequentially, each step with its own time scale. Our research focuses on the first two steps, collision and film drainage, which are dominated by hydrodynamic forces. We are able to study hydrodynamic forces in the coalescence process by shearing the emulsion. The rate of coalescence will be directly related to the change in drop size of the system, which will be measured by MRI Techniques through the use of the restricted diffusion theory. MRI is a non-invasive and insensitive technique that allows us to measure drop sizes and distinguish the difference between a cluster of small drops and one big drop. Preliminary results using a mixture of octane, water, and Tween 20 show that coalescence happens to a small volume percent of the oil, which leaves the rest of the emulsion mixture unchanged. Furthermore, this small population of drops become so big that they cream out of the emulsion affecting the flow field. These results will help in the development of emulsion systems that coalesces more homogeneously.