Lattice Boltzmann simulation of a drop impact on a moving wall with a liquid film

A liquid drop impact on a moving wall with a pre-existing thin film of the same liquid is simulated by using a two-phase flow lattice Boltzmann model. A perturbation to flow near the wall is introduced shortly after the moment of impact to reflect the instability of drop impact dynamics. The present simulations not only confirm the splash behavior of a drop impact on a stationary wall with the liquid film, but also reveal some interesting dynamics features of the drop impact on a moving wall with the liquid film. It is found that the moving wall can act to enhance or suppress the splash. The influence of a moving wall on the drop splashing is studied by examining the interface shapes, velocity and vorticity fields. The numerical results indicate that a critical threshold of wall velocity exists, which is determined by the Reynolds number, Weber number and the film thickness. If the wall velocity were larger than this critical value, only a part of the drop could splash on the wall.