Numerical study on impacting-freezing process of the droplet on a lateral moving cold superhydrophobic surface

Abstract For the impacting-freezing process of the droplet on cold surfaces, more studies have focused on stationary surfaces, while moving surfaces have received less attention. Here, a three-dimensional numerical model based on the VOF model and the Solidification/Melting model is established to numerically study the impacting-freezing process of the droplet on a lateral moving cold superhydrophobic surface, and focusing on the morphology evolution of the droplet and the initial freezing location. For the lateral moving surface, five different morphology distributions were observed during the impacting-freezing process of the droplet: full rebound, near full rebound, partial rebound, near full adhesion and full adhesion. The initial freezing location of the droplet preferentially appears on the upstream side of the droplet. The freezing on the downstream side of the droplet lags behind that of the upstream side due to the cooling effect of the cold surface, and the lagging effect is strongly influenced by the cold surface temperature. Moreover, the effects of cold surface temperature, supercooling degree and impacting Weber number on the spreading factor during the impacting-freezing process of the droplet are also discussed. The effect of the cold surface temperature on the spreading factor is greater than that of the supercooling degree. And a unified morphology distribution map of rebound and adhesion of the droplet is plotted based on the weighted average temperature and the impacting Weber number, which can show the competitive relationship between droplet impact hydrodynamics and droplet solidification.