Lattice Boltzmann simulation of droplet solidification processes with different solid-to-liquid density ratios

Droplet solidification is widespread in nature and industry. The difference in droplet density before and after solidification has a significant impact on the solidification characteristics of the droplet. In this research, a lattice Boltzmann model considering that difference is developed to simulate the droplet solidification process and is validated by comparing the simulation results with the analytical solutions and the experimental data. The triple contact line variation, solidification time, and final droplet profile are analyzed with a special emphasis on the effect of solid-to-liquid density ratio. As the density ratio increases, the triple contact line tends to go up but the droplet height decreases, leading to a shorter solidification time. In the final droplet profile, a tip or plateau is observed when the density ratio is smaller or larger than unity and the plateau radius increases at a larger density ratio. The effects of Stefan number (St), contact angle (CA), and Bond number (Bo) under different density ratios on the solidification process are further investigated. The increasing St and Bo, or decreasing CA reduces the solidification time. The Bo and CA mainly affect the solidification process by modifying the initial droplet profile. This work can provide a better understanding of the droplet solidification mechanisms and related applications.