Détails des cours

Freezing of solutions and formation of sea ice (Grae Worster)

The lectures will focus on the fundamentals of phase change and fluid flow associated with the solidification of multi-component systems.  The solidification of simple binary solutions (metallic alloys, aqueous salt solutions) will be exemplified by the formation and evolution of sea ice.  I will discuss the formation of mushy layers – two-phase media comprising a matrix of solid crystals and mobile interstitial melt – and their evolution, describing the different mechanisms by which solute can be redistributed: fractionation; brine-pocket migration (temperature gradient zone refinement); brine expulsion by expansion on phase change; flushing; and gravity drainage.  I will additionally describe some of the fundamentals of solidification of colloidal suspensions, drawing parallels and highlighting contrasts with the solidification of solutions.  The focus throughout will be on developing understanding by mathematical modelling.

Bio: Grae Worster completed his PhD at the University of Cambridge, UK in 1983.  His early career included being a Research Fellow at Trinity College Cambridge, 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 the 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.

Formation of snow crystals (Kenneth Libbrecht)

This course will examine the physical processes underlying the formation of ice crystals from water vapor in the laboratory and in the atmosphere, with a particular focus on explaining the remarkable changes in snow crystal growth morphology with temperature and supersaturation. Topics include:
> Ice surface structure: premelting, terrace step energies, and molecular dynamics
> Diffusion-limited growth: phenomenology of faceting and branching, free-dendrite growth, analytic solutions, and solvability theory
> Molecular attachment kinetics: terrace nucleation, faceting dynamics, and structure-dependent attachment kinetics
> Computational snow crystals: numerical techniques, cellular automata, 3D growth models
> Experimental snow crystals: laboratory techniques, growth measurements, designer snowflakes

Bio: Kenneth Libbrecht was educated at Caltech and Princeton, earning his PhD in physics in 1984. He then joined the faculty at Caltech, where his activities have included research in helioseismology, laser cooling and trapping of neutral atoms, diode laser technology, and the search for gravitational radiation from astrophysical sources. In the mid 1990's, Libbrecht's interest in the molecular dynamics of crystal growth led him into to a detailed study of how ice crystals grow from water vapor, which is essentially the physics of snowflakes. This ongoing endeavor seeks to better understand how crystals grow and how complex patterns emerge in the process. He has authored several books on this topic, including The Snowflake: Winter’s Frozen Artistry, Ken Libbrecht’s Field Guide to Snowflakes, and the recent physics monograph Snow Crystals: A Case Study in Spontaneous Structure Formation.

Ice accretion in aeronautics (Claire Laurent and Pierre Trontin)

> Introduction to icing in aeronautics (C. L.)
> Accretion modeling (C. L.)
> Super Large Droplets, ice-crystals and snow icing (P. T.)
> Anti-icind and de-icing issues(P. T.)

Bio:Claire Laurent is a research engineer at ONERA Toulouse, France. She obtained her PhD in Energetics and Transfers in 2008 from Université de Toulouse. Her PhD research activities were devoted to the study of the multi-component droplet vaporization for turbo-engine combustion chambers applications. Then, she was in charge of the development of the 3D wall liquid film solver in the multiphysics ONERA CFD code CEDRE and also work on modelling various multiphase phenomena to enrich the code with different models built from experimental work. The code was then progressively update to become a 3D accretion solver for icing applications, especially dedicated to the ice crystals icing in turbo jet engine.

Surface of ice and ice wetting (Daniel Bonn)

The class will discuss the surface of ice in all its facets. Its wetting properties, ice skating, self-healing of scratches, and pointy ice drops. The surface of ice can also undergo instabilities, leading for instance to the appearance of wavy icicles. The main question will be whether the existence of a molten layer of water on ice is necessary to understand the behavior of the ice surface.

Bio: Daniel Bonn is director of the Institute of Physics of the University of Amsterdam, where over 200 researchers work. He is also the group leader of the Soft Matter Group, which studies the flow behavior of surfactant, polymer, and colloid systems, and totals about 60 people. He published more than 300 papers on wetting, complex fluids and hydrodynamics. Daniel Bonn has a large number of industrial collaborations such as with Michelin, SKF and Unilever, Shell,  DSM, Akzo Nobel, ASML etc., and is co-founder of the successful startup company GreenA. He is a recipient of the Physica Prize, a Fellow of the American Physical Society, and was recently elected as a member of the Royal Dutch Academy of Sciences.

Freezing of suspensions and emulsions (Sylvain Deville)

The interaction of hard or soft objects with a moving solidification front is a common feature of many industrial and natural processes such as metal processing, the growth of single-crystals for photovoltaics and microelectronics, the cryo-preservation of cells, the formation of sea ice, or the preparation of frozen food. Solidification fronts interact with objects with different outcomes, from the total rejection to the complete engulfment of objects. Being able to understand and control the solidification dynamics and microstructure and the fate of the objects is of primary importance in these domains.
In this lecture, I will first present the different contexts in which the interaction of objects with a moving solidification front have been investigated, as well as the different experimental techniques that have been used or developed. I will then present our current understanding of the physics of the associated phenomena, starting from the simplest situations (hard particles) to more complex ones (soft objects). I will finally discuss the limits of our current understanding and control of these processes.

Bio: Sylvain Deville is a CNRS research director at the Institut Lumière Matière (ILM) in Lyon, France. He started freezing things during a postdoctoral stay at Lawrence Berkeley National Laboratory before joining the CNRS in 2006. His research interests revolves around freezing and span materials science, physics, soft matter, geophysics, and biophysics.

Freezing of soil and geomorphology (Alan Rempel)

We begin with the controls on solid—liquid phase partitioning and liquid transport in porous media. This leads into an analysis of force equilibrium, soil freezing regimes and conditions leading to segregated ice growth. We examine different approaches to modeling ice lens formation and survey the experimental evidence to support and differentiate them. We discuss how solidification of porous media affects glacier dynamics, and leads to frost cracking in cohesive materials. Finally, we explore the implications of our changing climate for the frost damage that results from freeze-thaw cycles.

Bio: Alan Rempel is Professor of Earth Sciences at the University of Oregon. He was trained in Applied Mathematics at Cambridge, following undergraduate and Master’s degrees in Engineering Physics and Geophysics from the University of British Columbia. His main academic interests center on mechanics problems, especially those involving phase changes and sliding, which sometimes combine as in the study of glacial transport.