Heinz G. Stefan Fellowship Award Ceremony with Distinguished Lecture by Prof. Grae Worster
Join us on Tuesday, March 14th at 3pm for a celebration of the 2023 Heinz G. Stefan Fellowship recipient Xiating Chen, with a distinguished lecture by Prof. Grae Worster.
Grae Worster, Professor of Fluid Dynamics in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge
Distinguished lecture: The dynamics of super-absorbent hydrogels
Abstract: Super-absorbent polymers placed in water can form hydrogels with polymer fractions of less than 1% by volume, with the water molecules being adsorbed by the hydrophilic polymer to form an elastic material. They are used in disposable diapers, for soil remediation, for controlled drug delivery and as actuators in microfluidic devices. The water is not fixed in place but can flow through the porous polymer scaffold to drive swelling and shrinkage. We have developed a new continuum-mechanical approach to modelling super-absorbent hydrogels, which allows for strongly nonlinear swelling while remaining linear in deviatoric strains, in effect treating hydrogels as instantaneously incompressible, linear elastic materials but with material properties that can vary strongly with polymer concentration. I will describe this model and illustrate its features by solving simple examples of swelling spheres, transpiration through cylinders, and by analysing a morphological instability that can arise during swelling.
About: Grae Worster completed his PhD at the University of Cambridge, UK in 1983. His early career included being an Instructor in Applied Mathematics at MIT and an Assistant Professor in Applied Mathematics and Chemical Engineering at Northwestern University. He is currently Professor of Fluid Dynamics in the Department of Applied Mathematics and Theoretical Physics, University of Cambridge UK, and until recently was Editor of the Journal of Fluid Mechanics. His research has included mathematical and experimental studies of buoyancy-driven flows and phase change, particularly in situations where these two phenomena interact, applying fundamental understanding to environmental problems including the mechanisms affecting brine drainage from sea ice, the flow and stability of marine ice sheets, and dynamics of frost heave. His focus has been on formulating mathematical descriptions of multi-component systems, including alloys, colloidal suspensions and, latterly, hydrogels. Since its foundation in 2003, Grae has been a regular lecturer at the African Institute of Mathematical Sciences (AIMS), and he wrote the first book in their library series on "Understanding Fluid Flow."
2023 Heinz G. Stefan Fellowship recipient Xiating Chen, advised by Prof. Xue Feng
Presentation title: Interaction between green infrastructure and urban hydrology at multiple scales
Abstract: Green infrastructure and other urban greenery are widely implemented to reduce stormwater runoff and mitigate urban heat island effects, but their hydrological functions and related dominant processes differ across scales (e.g., the local, green infrastructure scale, the catchment scale, the regional watershed scale). In this presentation, I will focus on the tree-level soil-plant-atmosphere continuum with preliminary experimental results from ash trees in the City of St. Paul. Using sap flux measurements (evapotranspiration), soil moisture and canopy temperature in urban trees, we reveal some important ecophysiological features that control the urban heat-vegetation-and-water dynamics. I hope to incorporate these physical observations into the watershed-scale understanding of green infrastructure performance, further providing empirical guidelines for integrating municipal forestry and water resources management.
About: Xiating Chen is a PhD candidate in water resources engineering at the St. Anthony Falls Laboratory studying under Professor Xue Feng. Her research is focused on eco-hydrological functions of urban trees and other green infrastructure at both local and watershed-scale, through combined field observations and modeling approaches. Xiating received her Bachelor of Science in Engineering degree from Duke University.