Date: November 22, 2019
Time: 1:00 – 1:50 pm
Location: CHBE Room 102
The Effect of Flow-Induced Concentration Nonuniformities on Shear Flow
In this talk, we begin by reviewing prior work from our group on the instability of simple viscometric (shear) flows, due to the coupling between stress and concentration in entangled polymer solutions. This work predicts that shear-induced migration resulting from these instabilities can lead to macroscopic banding of the polymer concentration profiles, and thus to a corresponding banding of the velocity profiles. This suggests one possible mechanism for shear banding in polymer solutions, often assumed in the rheological literature to be impossible given the monotonic nature of the relationship between shear rate and shear stress in homogeneous polymeric liquids. We then turn to our recent attempts to study the same problem experimentally. We show that measurements of the velocity profiles using particle tracking methods, and the concentration profiles using fluorescence imaging are consistent with these theoretical predictions.
Professor Leal obtained a BS, degree in chemical engineering from the University of Washington, followed by an MS and PhD degree from Stanford University where he carried out research under the direction of Prof. Andreas Acrivos. He then spent two years as a postdoctoral student in the Dept of Applied Math and Theoretical Physics at Cambridge University working with Prof G.K. Batchelor, prior to returning to faculty positions at Caltech (1970-89) and UCSB where he is a Research Professor and the Schlinger Professor of Chemical Engineering (Emeritus).
Research Interests: Laminar flows, Interfacial Phenomena including the dynamics of drops, bubbles and related membrane-based particles; The rheology and dynamics of Complex Fluids including polymeric fluids, suspensions, and emulsions;
Professional Activities and Awards: Fellow of the National Academy of Engineering,; Fellow of the American Academy of Arts and Sciences. Prof. Leal has received a number of other awards including: The Fluid Dynamics Prize of the APS; the Bingham Medal of the Society of Rheology; and the Allan P. Colburn, the William H. Walker and the Warren K. Lewis Awards of the American Institute of Chemical Engineers. He was identified in 2001 by ISI Thompson Scientific as one of the 100 Most Highly Cited Researchers in Engineering. He served as the editor of Physics of Fluids from 1998-2015, and is currently the co-editor in chief of Physical Review Fluids. He has also authored two textbooks, the most recent being “Advanced Transport Phenomena: Fluid Mechanics and Convective transport Processes” published by CUP. He has also directed the PhD research of more than 60 students, and authored or co-authored more than 300 archival papers.