Dynamic wetting is crucial to processes where liquid displaces another fluid (such as air) along a solid surface, an important example being the deposition of a coating liquid onto a moving substrate. Dynamic wetting failure occurs when the displacement happens too quickly, and this leads to entrainment of the receding fluid into the advancing liquid. In coating processes this entrainment compromises the quality of the final product, so it is desirable to develop a fundamental understanding of the factors that control the onset of dynamic wetting failure. In this talk, I will discuss how the interplay between experiments and modeling has enabled progress in this area. The experiments involve measurements of the critical speed at which wetting failure occurs and flow visualizations of air entrainment.
The modeling involves a combination of asymptotic analysis and two-dimensional finite element calculations that link the onset of wetting failure to limit points in families of steady-state solutions. The results reveal the mechanisms responsible for wetting failure and suggest strategies for delaying the onset of air entrainment in coating flows.
About the Speaker
Satish Kumar is a Professor in the Department of Chemical Engineering and Materials Science at the University of Minnesota. Prof. Kumar received his undergraduate degree from Minnesota (1993), and his master's (1994) and doctoral degrees (1998) from Stanford University, all in chemical engineering. Following postdoctoral work at Ecole Normale Superieure (Paris) and the University of Michigan, he joined the faculty at Minnesota in 2001.
Prof. Kumar currently serves as co-leader of the Coating Process Fundamentals Program at Minnesota and recently completed a two-year term as President of the International Society of Coating Science and Technology. He is a Fellow of the American Physical Society, and serves on the editorial boards of the Journal of Non-Newtonian Fluid Mechanics and the Journal of Engineering Mathematics. Prof. Kumar's research involves integration of transport phenomena, colloid and interface science, rheology, applied and computational mathematics, and experiments to address fundamental issues motivated by problems in materials processing. These fundamental investigations, which are described in 114 journal articles, are frequently inspired by industrial applications in areas such as coating and printing processes, polymer processing, nanofluidics/microfluidics, and energy.
Topics of current interest include dynamic wetting, interfacial instabilities, interfacial flows of suspensions, and polymer dynamics near surfaces.
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