Gareth H. McKinley

Gareth H. McKinley

2013 Bingham Medalist

Massachusetts Institute of Technology

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Gareth H. McKinley is a world renowned rheologist who has made broad ranging and penetrating contributions to rheology and non-Newtonian fluid mechanics. Amongst his many contributions, he is perhaps best known for his extensive experimental studies on extensional rheology and large amplitude oscillatory shear (LAOS) flow, and for elucidation of elastic instabilities and their mechanisms. Gareth’s contributions are captured in more than 200 publications, which have been cited more than 6000 times.

Gareth H. McKinley received his B.A. and M. Eng. in chemical engineering from University of Cambridge, Cambridge, England in 1985 and 1986, respectively, and his Ph.D. in chemical engineering from the Massachusetts Institute of Technology, Cambridge, Massachusetts, USA in 1991, the same year he became a member of The Society of Rheology. Gareth’s Ph.D. work was with Bob Armstrong and Bob Brown on the topic on LDV measurements of viscoelastic flow instabilities in complex polymer flows. Following his studies at MIT, Gareth joined the faculty at Harvard University in 1991 as Assistant Professor of Engineering Sciences, became Associate Professor of Natural Sciences in 1995, and moved to MIT in 1997, where he is School of Engineering Professor of Teaching Innovation and Associate Head for Research in the Department of Mechanical Engineering.

Gareth is one of the best and most respected experimentalists in the field of non-Newtonian fluid mechanics. In research, Gareth has shown considerable acumen at learning new areas and in synthesizing a variety of diverse topics into his research. Much of the success in his research is the result of his understanding not only the polymer chemical structure and rheology of the viscoelastic fluids he is studying, but also the nonlinear dynamics of these flows. This has led him to significant, new interpretations of viscoelastic flow phenomena. As a result, he was the first to develop a comprehensive map of flow transitions in a viscoelastic fluid. He has written significant papers on complex viscoelastic flows, including flow through abrupt contractions, flow near stagnation points (around cylinders and spheres), and torsional flow between parallel plates and between a cone and plate. These studies represent significant advances in viscoelastic fluid mechanics, by showing the evolution of flow families as important dimensionless groups are varied. Previously, the literature on these flows was restricted almost exclusively to illustrations of non-Newtonian behavior observed under isolated conditions of either high Deborah number or high Weissenberg number. The separation of Deborah and Weissenberg number effects in these experiments has led to his postulate of an appropriate dimensionless scaling for the onset of viscoelastic instabilities caused by an interaction of streamwise normal stresses and streamline curvature. Gareth is able to make connections between his experiments and nonlinear dynamics, and he in fact shapes his experiments based on the nonlinear theory.

Gareth is very perceptive and quick to see new, interesting problems. For example, in the course of rheologically characterizing the Boger fluids used in his research, he noticed the same kind of "antithixotropy" that had been noted previously on higher molecular weight samples, although this effect was thought not to occur for the particular molecular weight range he was studying. He became interested in the origin of the apparent increase in viscosity and through careful investigation was able to show that the observation results from a fluid-mechanical instability in the cone-and-plate or parallel-plate experiments used to measure viscosity and not from a feature of the rheology (i.e., antithixotropy). From his analysis he then showed that the critical onset point should depend on the Deborah number and not on the Weissenberg number or shear stress as had been supposed by others in the literature. He has furthermore discovered the fundamental structure of the spiral instabilities in these flows and provided a much needed set of experiments for modelers.

Early in his career, Gareth turned his attention to one of the most significant problems confronting experimental rheology, namely that of developing experimental methods for determining unambiguously the elongational properties of mobile polymer liquids. Gareth and his collaborators were instrumental in advancing and popularizing both the Tam Sridhar filament stretching extensional rheometer and the Vladimir Entov capillary breakup extensional rheometer for elongational flow rheology measurements of low- to moderate-viscosity fluids. He has developed microfluidic extensional rheometers using hyperbolic contraction and cross slot devices, as well as ultralow viscosity extensional rheometers measuring beads-on-a-string formation in a free jet. Altogether, he has over 60 publications on this topic, with more than 2000 citations, including an Annual Review of Fluid Mechanics article written with Tam Sridhar.

In recent years, Gareth has become an authority on large-amplitude, oscillatory shear flow (LAOS) measurements. Here he and his group have developed a technique and protocols for LAOS measurements and interpretation, and have used these developments to characterize wormlike micellar systems, gels, and slug mucus.

A measure of Gareth’s stature in the fields of rheology and non-Newtonian fluid mechanics is his service as Executive Editor of the Journal of Non-Newtonian Fluid Mechanics from 2001 through 2009 (and at a young age). During his tenure as Executive Editor the impact factor increased from 1.35 in 2001 to 2.00 in 2009. He currently serves on the editorial boards of the Journal of Rheology, the Journal of Non-Newtonian Fluid Mechanics, Rheologica Acta, and Applied Rheology. Gareth has been active in Society of Rheology governance, serving on the Executive Committee, on the Technical Program Committee, and on various standing committees.

Gareth has done much of his work in collaboration with graduate students and postdocs at Harvard and MIT. In the process of educating these students, he has produced a string of successful young rheologists and academics (eight to date). Many of his former students and postdocs gathered for a group photo in Lisbon in 2012.

Gareth enjoys the support and partnership of his wife Julie; together they have raised three great kids; Colin (19), Paige (17), and Miles (15). When his family was asked what they think their Dad likes outside of work, it sounded very much like rheology: The kids recount tales of experimenting/playing with dry ice that he brought home from work, the summer they had to leave the spider web on the front door and use the side door so as not to disturb the web making, and countless hours playing with ooobleck when they were little. Most recently, Gareth taught a program at the local children's museum with daughter Paige and he beamed with pride as she demonstrated ferro fluid (even though ultimately she wore a large amount of it.). There is nothing better than having a Dad who likes and actually encourages getting dirty in the pursuit of good science. When pressed, there are some non-scientific interests attributable to Gareth; including scuba diving, early morning runs, hosting students/colleagues at home, F1 motor racing, sports cars, the Tottenham Hotspurs football club, single malt scotch, and vintage port. If there’s a joke, a celebration, or a laugh, Gareth is all in.

In summary, Gareth is a leading figure and an influential, respected scholar in non-Newtonian fluid mechanics. His carefully executed, well thought-out experiments are viewed as definitive by the non-Newtonian fluid mechanics community. Gareth is truly deserving of the 2013 Bingham Medal from The Society of Rheology.