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Abstract:
Many processes in nature involve multiple, mechanically distinct phases: for instance, crystals settling in magmatic systems and ash particles interacting with a turbulent gas phase in an explosive volcanic eruptions. The interaction between these phases shape the landscape of all terrestrial planets, dictate exchanges at the interface of the solid surface and the atmosphere and lead to the large scale differentiation of Earth and other planets. Examples of multiphase flows include explosive volcanic eruptions, Martian dust storms, sediment-choked rivers, crystal and bubble-laden magma chambers and marine turbidity currents. Although extremely common, the cumulative expression of numerous particle-particle and particle-fluid interactions can produce emergent meso-scale structure and self-organization that is difficult to predict. I will address multiphase dynamics in the context of natural high-energy examples: planetary differentiation and volcanic eruptions. I will discuss the use of multiphase models in addressing the different scales of fluid motion in volcanic multiphase flow as well as how they can provide a platform to integrate microphysical, analogue experiments and observational constraints. Microphysical experiments can provide the necessary closure for statistical mechanics based models, and provide a way to examine grain-scale processes in a probabilistic manner. Such small-scale processes can dramatically alter the flow dynamics. One of the primary goals and utilities of this combined approach is that it enables comparison with diverse datasets, integrating previously disparate observations.
Bio:
Josef Dufek received a B.S. in Geophysical Sciences from the University of Chicago and a Ph.D. in Earth and Space Science from the University of Washington. He was a Miller Postdoctoral Fellow at the University of California, Berkeley, and joined the faculty in the School of Earth and Atmospheric Science at Georgia Tech in 2006. He is the recipient of the Hishashi Kuno award in 2010, the George Walker award in 2011, and the Macelwane Medal from the American Geophysical Union in 2012. He is a fellow of the American Geophysical Union, and is currently an Associate Professor in the School of Earth and Atmospheric Science and was recently named as Associate Chair for the School.
Josef Dufek studies physical processes in planetary interiors, volcanic eruption dynamics, and multiphase flows that shape the landscape. The Dufek lab is primarily focused on the application of fluid dynamics to understand mass and energy transfer in geological processes, with particular emphasis on volcanic systems. One of the Dufek lab’s research goals is to delineate how multiphase interactions contribute to the structure and composition of planetary interiors, and the role of such interactions in determining the dynamics and deposit architecture of volcanic flows using computational, experimental and field studies. Their research can be broadly grouped into two categories: 1) melting and mixing in the crust and mantle and the geochemical consequences of these processes, and 2) the dynamics of turbulent multiphase flows, and in particular the dynamics of explosive volcanic eruptions and particle laden gravity currents, such as pyroclastic flows or turbidity currents. The Dufek lab has recently been involved with projects at terrestrial volcanoes such as Tungurahua and St. Helens, and planetary flows on Mars and Enceladus.
