HR: 0800h
AN: C21B-0462    [Abstracts]
TI: A Micro-Structural Phase-Field Model for Snow Metamorphism and First Experimental Validations using Migrating Air Inclusions in Ice
AU: * Kaempfer, T U
EM: thomas.kaempfer@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory CRREL, 72 Lyme Road, Hanover, NH 03755, United States
AU: Plapp, M
EM: Mathis.Plapp@polytechnique.fr
AF: Laboratoire PMC - Ecole Polytechnique, Ecole Polytechnique, Palaiseau cedex, 91128, France
AU: Johnson, J B
EM: jerome.b.johnson@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory CRREL, 72 Lyme Road, Hanover, NH 03755, United States
AU: Sturm, M
EM: matthew.sturm@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory CRREL, 72 Lyme Road, Hanover, NH 03755, United States
AB: Snow is a highly porous medium consisting of an ice matrix and porous space containing water vapor. Moreover, snow undergoes metamorphism as heat flow and interface effects induce mass flow and thus profoundly change the microstructure, i.e., the distribution of ice and pores. Reciprocally, this evolution influences the thermophysical, chemical, and mechanical properties of snow. In particular, the microstructure of snow influences the heat conductivity as heat transport consists in (i) heat conduction in the ice and pores, (ii) heat transport related to water vapor diffusion in the pores, and (iii) latent heat release and gain due to phase changes at the ice-pore interfaces Recently, detailed image series of metamorphosing snow using computed X-ray micro-tomography (micro-CT) became available and models for heat conduction through a steady state ice and pore network emerged. We present a phase-field model to solve the coupled heat and mass transport problem including phase-change processes in an evolving ice-pore network. The model considers mass fluxes that are induced by temperature gradients in the snow as well as by curvature effects and handles topological changes of the microstructure implicitly. We apply the model to 3D micro-CT data of snow. The simulations agree qualitatively well with laboratory observations and underline the strong link between microstructure and heat conductivity of snow. In order to validate the model quantitatively and to constrain the model parameters, simpler experiments than snow metamorphism observations by micro-CT are needed. We designed a relatively simple experimental apparatus to observe the migration of air inclusions in ice subjected to a temperature gradient. Considerable insulation and good temperature control at the hot and cold sides of an ice block allow us to impose a nearly constant and mono-dimensional temperature gradient. Small air inclusions can be inserted into the ice for example by drilling. The advantage of using a rather big ice-block with small inclusions instead of the sparse and intricate ice matrix as it would be for snow is that a much better temperature control can be achieved. The migration of the inclusions through the ice for given temperature gradients is observed by digital photography and migration velocities can be computed. We use this experimental data to constrain the phase-field model parameters by comparing it to simulated ice inclusion migrations.
DE: 0736 Snow (1827, 1863)
DE: 0738 Ice (1863)
DE: 0766 Thermodynamics (1011, 3611, 8411)
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2007 Fall Meeting