U.S. Department of Energy

Pacific Northwest National Laboratory

Extreme transitions of flow properties in mixtures: discontinuous shear thickening & hydrate jamming

You’re invited to attend an NPSI-sponsored Brown Bag Seminar on Friday, October 23, 2015, from 11:00 - Noon in the CSF Mural Room 1508, featuring Dr. Jeffery Morris from the Levich Institute and the Department of Chemical Engineering for the City College of New York.

Friday, October 23, 2015
Dr. Jeffrey Morris
Acting Director
Levitch Institute
This talk will discuss two quite different extreme transitions in flow properties observed in multiphase mixtures. The first case is abrupt or discontinuous shear thickening (DST), which occurs as shear rate is increased in suspensions at large solid fraction. For many years, DST has been known, and popular videos of running on oobleck (cornstarch suspended in water) are found on-line. Yet the fundamental basis has been mysterious and controversial. A simulation based on a quite minimal model—including viscous, electrostatic repulsion and contact frictional interactions between particles—has been shown to reproduce DST as the rate is increased. The mechanism is found to rely on a contact network between the particles, which changes dramatically as the critical shear rate is surpassed. In the second case, properties of hydrate-forming water-in-oil emulsions will be described based on our experiments. This is a critical problem in petroleum pipeline transport: here a transition occurs due to a reaction as time progresses. Hydrates are solid crystalline compounds formed by water and small organic molecules (we focus on cyclopentane) at low temperatures; they form a solid layer at the water-oil interface of emulsified drops. Morphology of the hydrate under emulsified conditions is typically needle-like and porous. The developed porosity allows even modest internal phase (water) emulsions to jam: the low-viscosity emulsion develops a large viscosity and eventually a large yield stress as hydrate formation progresses—much like the undesirable plugging of pipelines. The rheological properties will be correlated to direct imaging of the hydrate crystal growth at a water-oil interface to illustrate the role of the hydrate porosity
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