Abstract: This talk will discuss extreme transitions in flow properties 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. 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.

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 phase transition 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 and is able to “jam”, much like the undesirable plugging of pipelines.  The rheological properties will be correlated to direct imaging of the hydrate crystal growth process.

Bio: Ph.D. Caltech, 1995. Postdoc: Shell Research BV (KSLA, Amsterdam), 1994-1995; Georgia Tech: Assistant Professor, 1996-2002; Senior Scientific Advisor, Halliburton 2002-2004; City College of New York, CUNY: Associate Professor (2005-2008), Professor (2008-Present), Chair of Chemical Engineering (2013-Present), Acting Director, Levich Institute (2015-Present).

Research by the Morris group is based on development of a fluid mechanical description appropriate for complex fluids, particularly suspensions and colloids, with recent focuses on the interaction of frictional interactions with viscous forces in suspensions, and the interaction of particles with fluid interfaces.  Applying simulation and experiment, combined with ideas of statistical and continuum mechanics, the research seeks to develop understanding of flow-induced microstructure and the resulting mixture rheology. Of particular interest are rheologically-induced phenomena unique to mixtures, including bulk particle migration.  In addition, the group has active projects in gas-hydrate emulsions. He has held Visiting Professor positions at Brown University (Applied Math) the Université de Paris Sud (at the Laboratory FAST) and Université de Provence (at the Laboratory IUSTI), and served as a visiting Director of Research at the CNRS, all in France. He authored the text A Physical Introduction to Suspension Dynamics, with E. Guazzelli. For present work see the URL below: 

http://www-levich.engr.ccny.cuny.edu/~jmorris/