Abstract:

The freezing of water within porous media entails a variety of dynamics in which micro-and macro-scale phenomena blend. Among many, soil expansion, produced by ice segregation and underground water drawn therein by the freezing process itself, is one of the most striking manifestations and it is known to as frost heave.

The dynamics of premelted liquid films at ide-solid interfaces underpin a broad class of interactions in sub-freezing environments. A particularly important manifestation is thermal regelation, namely the migration of particles through an ice matrix under an imposed temperature gradient. In this process, enhanced melting on the warmer side of an inclusion and refreezing on the colder side drive particle motion relative to the surrounding ice. The premelted film constitutes a thin fluid domain in which pressure and temperature gradients induce a flow coupled with phase change at the film boundaries which are also subjected to van-der-Waals forces. This links nano-scale interfacial physics to macro-scale transport phenomena.

The thickness of the liquid layer, however, is sually only a few nanometres and this makes infeasible the direct simulation of these systems even for micrometric particles. Nevertheless, exploiting the flexibility of numerical modelling, it has been possible to conceive configurations with an artificially thick premelted layer such to make the numerical simulation possible and yet retaining the dynamics of the real physical process.

In this seminar, numerical simulations of thermal regelation will be presented showing results in excellent agreement with the theory and allowing to analysis of configurations in which simplified theories fail.

Introduction of speaker:

Roberto Verzicco is professor of Fluid Dynamics at Gran Sasso Science Institute in L'Aquila, Italy. Since 2010 he is also part-time Professor at the University of Twente.He received his M.S. in Aeronautic Engineering (1991) and Ph.D. in Aerospace Engineering (1994) both from University La Sapienza in Rome. His research, in the fields of experimental and numerical fluid dynamics, includes direct numerical simulation of turbulent flows, convective turbulence and bio-fluid mechanics. Since 1993 he has published more than 300 papers in international journals with 3 solicited reviews. He has published a monographic book on Immersed Boundary Methods with Cambridge University Press.He has organized several international conferences, workshops and colloquia and in 2012 he chaired the 9th European Fluid Mechanics Conference in Rome. Since 2012 he is Associate Editor of the Journal of Fluid Mechanics and since 2025 he is the President of Euromech. In November 2005 he received the Frenkiel Award 2005 from the American Physical Society for his studies on natural convection and in 2022 the Corrsin Award for the immersed boundary method. In 2012 he was elected EUROMECH Fellow and in 2013 APS Fellow.

审核：刘有晟、游小清