Freezing and capillarity

My first work was on the interaction of freezing and flow at small scales. I did my PhD between 2016 and 2019 at ∂'Alembert Institute, in Paris, France, under the supervision of Thomas Séon and Christophe Josserand. The goal was to study the impact of water drops on cold substrates. I keep working on related subjects, notably the shape of air bubbles trapped in ice.
Fracture Fracture

The shape of air bubbles trapped in ice

Frozen bubbles

PhD : Impact and solidification of water drops

Whenever a water drop impacts a cold surface – whose surface temperature is lower than 0°C – it freezes as it spreads. The solidification slows the drop's spreading down, eases its fragmentation into droplets, leads to the liquid's retraction and gives the frozen drop a certain shape. The nature of the cold surface is crucial in the freezing process. Starting from the Stefan problem, we developed a model for the solidification dynamics, which takes into account the thermal diffusion within the substrate. This model yields a better appreciation of the influence of the substrate's thermal properties – its temperature and thermal effusivity – over the liquid's rate of freezing. It enables us to quantitatively predict the dynamics of solidification, and therefore to study the freezing of a drop during its impact. As regards the drop's spreading, we demonstrated that the effect of freezing could be assimilated to that of viscosity, as it slows the flow down. We showed that the fragmentation of a drop at low temperature was due to an increase in the density of air. Once spread, the drop is trapped by the ice, which hinders its retraction. We established a link between the shape of the spread drop and the duration of its trapping. Finally, we showed that the competition between the retraction of liquid water on ice and its freezing led to the different patterns observed.


Pictures from my work have been selected by Art in Research, and FY Fluid Dynamics.
This video, which sums up my PhD, was presented in 2018 at the Gallery of Fluid Motion.
Gallery of Fluid Motion 2016 Gallery of Fluid Motion 2017