The evolution of droplet impacting on thin liquid film at superhydrophilic surface

摘要

Thin films are ubiquitous in nature, and the evolution of a liquid film after droplet impact is critical in many industrial processes. In this paper, a series of experiments and numerical simulations are conducted to investigate the distribution and evolution features of local temperature as the droplet impacts a thin film on the superhydrophilic surface by the thermal tracing method. A cold area is formed in the center after droplet impacts on heated solid surfaces. For the droplet impact on thin heated liquid film, a ring-shaped low temperature zone is observed in this experiment. Meanwhile, numerical simulation is adopted to analyze the mechanism and the interaction between the droplet and the liquid film. It is found that due to the vortex velocity distribution formed inside the liquid film after the impact, a large part of the droplet has congested. The heating process is not obvious in the congested area, which leads to the formation of a low-temperature area in the results.