Three-dimensional study of double droplets impact on a wettability-patterned surface

TL;DR

This study uses a 3D lattice Boltzmann model to analyze how wettability differences, Weber number, and droplet spacing influence the impact, rebound, and coalescence behaviors of double droplets on patterned surfaces.

Contribution

It introduces a detailed 3D simulation approach to understand the complex impact and rebound behaviors of double droplets on wettability-patterned surfaces, highlighting the effects of various parameters.

Findings

Droplets tend to rebound or migrate toward less hydrophobic areas due to unbalanced Young's force.

Contact time decreases with increasing wettability difference.

Droplet spacing influences coalescence and division patterns during impact.

Abstract

The directional movement and rebound behaviours of two droplets simultaneously impacting a designed flat surface with wettability difference is investigated based on the three-dimensional multi-relaxation-time pseudopotential lattice Boltzmann model. The effects of several factors, such as wettability difference, Weber number and droplet spacing on the directional movement and rebound behaviours are investigated in detail. The numerical results show that the unbalanced Young 's force caused by the wetting difference will cause the droplets to rebound or migrate laterally toward to the side with lower hydrophobicity on the surface, and the contact time of the droplets is found to decrease with the increase of the wetting difference. In addition, it is noted that there exists a secondary spreading behavior in the case of a lower Weber number, which in turn leads to an increase in contact time. Further, as far as the influence of the droplet spacing is concerned, we found that the coalescence intensity of the droplets decreases with the increase of droplet spacing, and in particular, the coalescing droplets are found to divide into two sub-droplets during asymmetric contraction, and three detachment patterns are then defined to reveal the effects of the droplet spacing.