Ejecta size distributions from large-scale molecular dynamics simulations of the high velocity impact of droplets of liquid metal on rigid and liquid surfaces

The impact of a solid or liquid drop on a rigid/solid or liquid surface, and the possible breakup that may result (the so-called splashing), is a frequently encountered phenomenon in shock physics. However, the mechanisms at the origin of the drop fragmentation are not yet well understood. This comes, on the one hand, from the difficulty to characterize experimentally a phenomenon which occurs at sub-microsecond timescales and sub-micrometer lengthscales, and, on the other hand, from the difficulty to simulate such a process from hydrocodes having no fragmentation models in their equations. To bring insight in the physics of fragmentation during splashing, we perform large-scale molecular dynamics (MD) simulations of the impact of droplets of liquid tin on rigid and liquid surfaces, with velocities ranging from 300 m/s to 1500 m/s. We measure the resulting secondary particle (ejecta) size distributions, and we show that they are different following the fragmentation mechanisms involved. The implementation of ejecta size distributions measurements in experiments should be therefore considered as helpful to improve the understanding of splashing physics.