On the 17th of December 2019, Rémi Granger will defend his PhD entitled "Crystal growth physics in dry snow metamorphism: characterisation and modeling of kinetic effects"
This PhD project was supervised by Christian Geindreau (3SR) and Frédéric Flin (CEN).
The defense will take place at 9:30 am in the conference room of the LEGI (K118).
The main objective of the thesis is to improve our understanding of faceting occuring during dry snow metamorphism. The thesis focuses on the interplay between heat and mass diffusion, and kinetic effects in the context of snow. For the first time, Diffraction Contrast Tomography (DCT) has been performed to monitor an experiment of temperature gradient metamorphism. The technique permits retrieval of the crystalline orientation of the grains constituting the microstructure of the sample. Links between orientation of crystals and mass fluxes were analysed.
The study shows that kinetic differences between basal and prismatic faces have effects on phase change fluxes at the ice/air interface.
From a numerical modeling point of view, a highly anisotropic kinetic coefficient has been taken into account for the evolution of the ice/air interface. The model uses the phase-field approach and couples phase changes to heat and water vapor diffusion.
The model was compared to an experiment of air cavity migration under a temperature gradient in a monocrystalline ice block monitored with X-ray microtomography, and to the growth of a negative crystal during a pumping experiment followed with optical microscopy.
Such anisotropy permits reproduction of the observed faceting.
Finally, the potential of the porposed model to describe snow metamorphism is highlighted.