Cold granular targets slow the bulk freezing of an impacting droplet

• 成果类型: Article
• 署名作者: Zhao, Song-Chuan; Zhang, Hao-Jie; Li, Yudong
• 署名单位: Xi'an Jiaotong University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11203
• DOI: 10.1073/pnas.2311930121
• 发表日期: 2024-01-09
• 关键词: supercooled water drops; raindrop-impact; ice; DYNAMICS; physics; FORCE; sand

摘要

When making contact with an undercooled target, a drop freezes. The colder the target is, the more rapid the freezing is supposed to be. In this research, we explore the impact of droplets on cold granular material. As the undercooling degree increases, the bulk freezing of the droplet is delayed by at least an order of magnitude. The postponement of the overall solidification is accompanied by substantial changes in dynamics, including the spreading-retraction process, satellite drop generation, and cratering in the target. The solidification of the wetted pores in the granular target primarily causes these effects. The freezing process over the pore dimension occurs rapidly enough to match the characteristic timescales of impact dynamics at moderate undercooling degrees. As a result, the hydrophilic impact appears hydrophobic, and the dimension of the solidified droplet shrinks. A monolayer of cold grains on a surface can reproduce these consequences. Our research presents a potential approach to regulate solidified morphology for subfreezing drop impacts. It additionally sheds light on the impact scenario of strong coupling between the dynamics and solidification.