| 论文简介 |
The effect of substrate temperature is investigated experimentally on the ice profile of an impact water droplet. A hydrophilic substrate, a relatively high impact velocity which can lead to a larger contact area, and a low surface temperature are employed aiming at enhancing the heat transfer rate through the droplet. The frozen droplet is uniquely central-concave at low surface temperatures, in contrast to the widely observed central-pointy ice formed at cold surfaces. The formation of the central-concave icing is attributed to the additional interior circular-like freezing front advancing both upwards and outwards during the solidification. Upon decreasing the surface temperature, the nucleation is triggered earlier, and the freezing rate is higher than that of a quasi-steady droplet freezing on a similar subcooled surface due to the impact-induced flattening of the droplet. A freezing regime map described by the dimensionless number representing the heat conduction rate through the substrate and Weber number consists of two regimes for the formation of the central-pointy and central-concave ice profile respectively. |
(创新港)
