Lattice Boltzmann study on the dynamics of successive droplets impact on a solid surface

Three dimensional computations on successive droplet impingement on a solid surface are reported. A high-density ratio based lattice Boltzmann model is employed for the present two phase computations and a geometric-based contact angle formulation is used to model the moving contact line. The focus of the present work is on the impact behaviour and the interaction dynamics between the impinging droplets with an initial gap. The effects of trailing drop velocity, surface wettability, drop viscosity and surface tension on the time-dependent dynamics are investigated during the impingement process. Two different transient interaction modes are observed for different velocity ratios. With increase in advancing contact angle, it is observed that primary spreading increases in the case of in-phase mode of collision. Effect of eccentricity, through the offset between the droplets, is found to result in an asymmetric evolution of droplet morphologies. Passive particle tracers are seeded inside the droplets to visualize mixing process as a time sequence of closely interacting droplets during the impact with a solid surface.