Gravity-driven spreading of a solidifying melt

Gravity-driven flows are ubiquitous in both nature and engineering applications and hence they have been widely studied both theoretically and experimentally. In many instances though, viscous spreading is coupled with cooling and solidification. Examples can be found in nature, e.g., lava flows and polythermal ice sheet dynamics, and in industrial applications, as in continuous casting. Several theoretical and a few experimental works have tried to study this phenomenon; however, in most cases the tested fluids do not capture the complex non-linear rheology that is expected in natural and industrial settings. In this talk we explore gravity-driven flows of a solidifying model melt composed of a paraffin-oil solution. Above the liquidus temperature this model melt is a simple Newtonian fluid, while below, it shows a continuous crystallization process that transforms the fluid to a visco-plastic suspension of crystals. We focus on fixed-volume release experiments over a flat surface and explore the effect of basal solidification on the flow dynamics. We record the spatial and temporal evolution of the advancing liquid and solid fronts and compare our results with a theoretical model of the underlying transport phenomena coupled with the rheology of the melt.