Normal impact of an ice particle on a water film

The present study experimentally investigated the normal impinging of an ice particle on a water film. The influences of Stokes number and dimensionless water film thickness were carefully analyzed. The dry surface, the room temperature water film, and the supercooled water film (−5.0 °C) were used as the impact targets. The restitution coefficient of the ice particle and the crown evolution were also analyzed. The results showed that, under the current experimental conditions, four kinds of phenomena happened: rebound with no fragmentation, rebound with fragmentation, no obvious rebound or crown, and obvious crown. The temperature of water film had a significant effect on the boundary between no obvious rebound or crown and obvious crown. As for the cases when the ice particle impacted the dry surface, the restitution coefficient decreased with the increasing impact velocity. In addition, the restitution coefficients in the room temperature water film cases were generally larger than those in the supercooled water film cases. As for the crown evolution, the dimensionless crown base diameter generally increased with the enlargement of the dimensionless water film thickness. An empirical correlation was proposed to predict the evolution of crown base radius. In addition, the dimensionless water film thickness had no apparent effects on the dimensionless crown height.