Simulation of impact of a hollow droplet on a flat surface

Despite many theoretical and experimental works dealing with the impact of dense continuous liquid droplets on a flat surface, the dynamics of the impact of hollow liquid droplets is not well addressed. In an effort to understand dynamics of the hollow droplet impingement, a numerical study for the impact of a hollow droplet on a flat surface is presented. The impingement model considers the transient flow dynamics during impact and spreading of the droplet using the volume of fluid surface tracking method (VOF) coupled with the momentum transport model within a one-domain continuum formulation. The model is used to simulate the hydrodynamic behaviour of the impact of glycerin hollow droplet. It is found that the impact and spreading of the hollow droplet on a flat surface is distinctly different from the conventional dense droplet and has some new hydrodynamic features. A phenomenon of formation of a central counter jet of the liquid is predicted. With the help of simulations the cause of this phenomenon is discussed. Comparison of the predicted length of the central counter jet and the velocity of the counter jet front shows good agreements with the experimental data. The influence of the droplet initial impact velocity and the hollow droplet shell thickness on the impact behaviour is highlighted.