Vendredi 21 novembre à 11h00, salle 359 - IUSTI
Abstract: Upon impact on a solid or liquid interface, a drop deforms, spreads, and retracts. Depending on the temperature of the interface, the drop can solidify during impact, leading to a wide range of solidified shapes. A liquid interface is defect-free for solidification, and a wider variety of behaviors can be observed upon impact. This study investigates the impact of a drop onto a liquid interface cooled down below the freezing temperature of the drop. Our goal is to study the competition between spreading and solidification, and to rationalize the morphology of solidified drops as we vary different parameters such as thermal shock, impact velocity and substrate thickness. More specifically, we propose a model for the nucleation and growth of crystals on the interface. Through comparing the characteristic times of phenomena at play in our experiments (impact, thermal transfer, solidification), we show that the timescale for the crystals to cover the interface is of the same order of magnitude as the hydrodynamic time. Comparison of these timescales allows to predict the transition from flat to concave shapes.