In this work, a new three-dimensional sessile droplet freezing model, involving the ice fraction and ice distribution after the droplet recalescence, is established based on the many-body dissipative particle dynamics with the energy conservation method for the first time. The proposed model is verified by comparing it with experimental results, and the accuracy of this model increases as the ice distribution becomes more non-uniform after recalescence. Furthermore, the effects of surface contact angle, droplet volume, surface temperature, and droplet supercooling degree on the freezing process are investigated in detail. The numerical results demonstrate that the angle of ice tips maintains a constant under various conditions. The upper and lower limits of solidification time under specific conditions are derived, and the droplet solidification time decreases linearly with the increase in supercooling. In addition, the average droplet solidification rate decreases with the increase in droplet volume, contact angle, and surface temperature, and the surface temperature is demonstrated to have the greatest influence on the solidification rate. Emphatically, we put forward an empirical formula, as a function of droplet volume, contact angle, droplet supercooling degree, and surface temperature, to predict the freezing time of a sessile supercooled droplet.

This work presents an experimental study on the splashing behaviors of drops impinging on rough solid surfaces. Most prior studies have shown the increase in surface roughness can promote the occurrence of a drop splash. Interestingly, we found two opposite effects of surface roughness on the drop splash that the increase in surface roughness can promote splash of low-viscosity drops but suppress splash of high-viscosity drops. According to the wetting state of the spreading lamella on rough surfaces, the splash regime can be classified into two modes: corona splash and prompt splash. It is found that the increase in surface roughness can promote the prompt splash but suppress the corona splash. The increase in surface roughness could provide wide channels for air to escape and suppress the corona splash. Meanwhile, the larger surface roughness could also disrupt the expanding lamella and promote the prompt splash. The dimensionless parameter Ohr can be used to distinguish two splash regimes, and the critical value Ohrc is obtained from experimental results, at which the splash regime changes from the prompt to corona splash. Emphatically, we obtain the splash criteria in two regions, which could reflect the opposite effects of surface roughness on the drop splash and successfully characterize the splashing behaviors in this work and previous studies. The results of this work are expected to provide valuable insights to control the drop splash in industrial applications.