Surface roughness effect on a droplet impacting a thin film using pseudo-potential lattice Boltzmann method

A tunable surface tension pseudo-potential lattice Boltzmann method (LBM) is applied to study a droplet splashing on a thin film over a rough surface. Our study focuses on the crown evolution processes influenced by various roughness parameters, including the protrusion height and the distance between two protrusions. The total kinetic energy of the crown is introduced to study the evolution process. The results indicate that more kinetic energy is consumed in the collision process and that the crown has a shorter dimensionless height in the case of a rough surface than with a flat surface. A threshold dimensionless protrusion height exists at which the energy consumption is minimized and the crown height is maximized. The dimensionless distance between two protrusions may affect the symmetry of the liquid crown but does not influence the kinetic energy consumed in the impact process. Neither the protrusion height nor the distance between two protrusions has a significant effect on the crown radius evolution process. This study shows that the proposed LBM pseudo-potential model is an effective tool for predicting the process of a droplet impacting a thin film in the presence of complex boundaries.