Pattern formation during freezing flow through a Hele-Shaw cell

Multiphase flow through subfreezing porous media is ubiquitous in a wide range of applications including snow and permafrost hydrology, cryopreservation and material design and manufacturing. These processes involve the complex interplay amongst interfacial flow mechanics, phase change and heat transfer, giving rise to a myriad of non-equilibrium phenomena that remain to be better understood.

In this work, we investigate the pore-scale physics of fluid flow through subfreezing porous media using the simplified geometry of a circular Hele-Shaw cell. The cell is initially air-filled and its bottom plate is maintained at a fixed subfreezing temperature. We then perform radial injection of water at a fixed rate and temperature. We use fluorescein sodium salt as a tracer and UV light illumination, which allows us to distinguish between the water and ice phase and their varying volume fraction across the Hele-Shaw cell gap. By varying injection rate (1mL/min- 5mL/min), injection fluid temperature (4°C, 20°C) and cooling plate temperature (-15 °C, -10°C, -5 °C), we present a phase diagram of the flow pattern during freezing imbibition. The results capture how imbibition and solidification co-evolve to create complex patterns ranging from a straight but tapering channel to a meandering channel and ice terraces.