## Spring 2019 - Seminar Series

#### George Haller, Ph.D., ETH Zurich, Switzerland

**Barriers
to tracer transport in fluid flows**

**Abstract**

Observations of tracer transport in fluids generally reveal highly complex patterns shaped by an intricate network of transport barriers. The elements of this network appear to be universal for small diffusivities, independent of the tracer and its initial distribution.

In this talk, I will first review prior, purely advective approaches to transport barrier detection. Next, I will discuss a mathematical theory to predict diffusive transport barriers and enhancers solely from the flow velocity, without reliance on expensive diffusive or stochastic simulations. This theory yields a simplified computational scheme for diffusive transport problems, such as the estimation of salinity redistribution for climate studies and the forecasting of oil spill spreads on the ocean surface. I will illustrate the results on turbulence simulations and observational ocean velocity data.

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** ****About the Speaker**

George Haller received his Ph.D. in Applied Mechanics at the California Institute of Technology in 1993. He then spent a year as postdoc at the Courant Institute of Mathematical Sciences at New York University, prior to joining the Division of Applied Mathematics at Brown University as Assistant Professor in 1994. In 2001, he left Brown University as Associate Professor to join the Department of Mechanical Engineering at the Massachusetts Institute of Technology, where he became Professor in 2005. While still a professor at MIT, he became the first director of Morgan Stanley's Mathematical Modeling Center in Budapest, which he headed for three years. He then joined the Department of Mechanical Engineering at McGill University in 2009, serving as Department Chair till 2011. Over the period 2014 -2018, he headed the Institute for Mechanical Systems at ETH Zurich, where he is currently Professor of Nonlinear Dynamics. Professor Haller has served on the editorial boards of the SIAM Journal for Mathematical Analysis, the Journal of Discrete and Continuous Dynamical Systems and the Zeitschrift für Angewandte Mathematik und Physik (ZAMP). He is currently Senior Editor at the Journal of Nonlinear Science and Associate Editor at the Journal of Applied Mechanics. His honors include a Manning Assistant Professorship at Brown University, an Alfred P. Sloan Research Fellowship in mathematics, an Albert Szent - Gyorgyi Fellowship, an ASME Thomas J.R. Hughes Young Investigator Award, an Honorary Doctorate from the Budapest University of Technology and Economics and a Faculty of Engineering Distinguished Professorship at McGill University.