Please join the University of Washington Department of Chemical Engineering for the lectures by
Prof. L. Gary Leal
Research Professor and the Schlinger Professor of Chemical Engineering (Emeritus)
University of California - Santa Barbara
Monday, May 22
4:00 - 5:00 p.m. (reception at 3:30 p.m.)
The Dynamics of Polymeric Solutions: Polymer Migration and Inhomogeneous Flow Effects
Polymeric solutions are an example of a complex fluid. This name has been coined to describe a broad class of fluids, most of which are multicomponent, exemplified by solutions of polymer in small molecule solvents, suspensions of particles, emulsions, micellar solutions of surfactants, suspensions of biological cells, and many other familiar materials. A key feature of such fluids is that the longest timescales for relaxation of the microstructure from a deformed state back to an equilibrium structure can range up to tens of seconds, so that the action of even relatively mild flows can push the microstructure into highly non-equilibrium configurations.
This means that the macroscopic properties of the fluid will change when they undergo a flow (even if the system is isothermal) in contrast to Newtonian fluids. Thus, complex fluids are typically non-Newtonian or viscoelastic. Due to the importance of complex fluids in materials processing or biological applications, there is a relatively well developed subject of non-Newtonian fluid mechanics. A key common assumption in theoretical studies of the flow of complex fluids is that they remain homogeneous—i.e. that the concentration of the disperse phase remains independent of position, even though it is known that it is possible for particles or macromolecules to migrate across velocity gradients, perpendicular to the flow direction. In the present work, we study polymeric solutions. We show that they do not necessarily remain homogeneous in flow. This fact, plus the coupling of the stress to concentration, means that even a simple shear flow can exhibit a linear instability at very low Reynolds number, and that this instability leads to a shear-banded steady state velocity profile. In shear banding, the velocity profile typically exhibits two regions of linear shear flow, but with different shear rates. This simple example suggests that flow induced concentration inhomogeneity can lead to major changes in a flow, and that it is a dangerous assumption to assume that a flowing complex fluid is homogeneous.
Tuesday, May 23
12:30 - 1:30 p.m.
Fluid Mechanics: Some Topics of Special Relevance to ChemEs
Fluid mechanics is a very old subject, some would say dating back to the water works of ancient Greece, or the more “modern” flow visualization studies of Leonardo da Vinci. Yet, I believe that it remains one of the most vibrant areas of research. In this talk, I will briefly address this dichotomy, which some might see as a contradiction. Then I will turn to aspects of the subject that are of special relevance to chemical engineers. This part of the talk will be focused primarily on flows dominated by viscous effects, often called Stokes flow or creeping flow. Although this subject dates back more than 100 years to the British mathematician George Gabriel Stokes, it remains a topic of great current interest due to the recent focus on small scale phenomena such as the motion (swimming) of biological micro-organisms, but it is also a topic where one’s intuition based upon everyday experiences may often be misleading. The examples I will discuss are intended to illustrate this point. If time allows, I will also introduce aspects of two other topics, namely flows driven by capillary forces at fluid interfaces, and flows involving viscoelastic fluids, both of which also exhibit phenomena that often seem surprising, and are of great importance to chemical engineers.
About Prof. L. Gary Leal
Prof. L. Gary Leal obtained a BS degree in chemical engineering from the UW, followed by an MS and PhD from Stanford. He then spent two years as a postdoctoral student at Cambridge, 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). He is a Fellow of the National Academy of Engineering and Fellow of the American Academy of Arts and Sciences. Prof. Leal’s honors include 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 AIChE.
About Prof. Bruce A. Finlayson
The Lecture, named in honor of Dr. Bruce A. Finlayson, Rehnberg Chair Professor Emeritus of Chemical Engineering, features distinguished chemical engineers who demonstrate exceptional scholarship, teaching, and service in their field. Dr. Finlayson has taught chemical engineering and applied mathematics at the University of Washington for 40 years, serving as chair of the Chemical Engineering Department from 1989 to 1998. He received the prestigious Walker Award from the American Institute of Chemical Engineering for his contributions to chemical engineering literature. He is a member of the National Academy of Engineering and served as president of the American Institute of Chemical Engineers.
Past Finlayson Lectures featured Drs. Eric W. Kaler (2013), John F. Brady (2014), Klavs Jensen (2015) and Ed Cussler (2016).