Abstract
One of the simplest splashing scenarios results from the impact of a single drop on a
deep pool. The traditional understanding of this process is that the impact generates
an axisymmetric sheet-like jet that later breaks up into secondary droplets. Recently
it was shown that even this simplest of scenarios is more complicated than expected
because multiple jets can be generated from a single impact event and there are
transitions in the multiplicity of jets as the experimental parameters are varied.
Here, we use experiments and numerical simulations of a single drop impacting on a
deep pool to examine the transition from impacts that produce a single jet to those
that produce two jets. Using high-speed X-ray imaging methods we show that vortex
separation within the drop leads to the formation of a second jet long after the
formation of the ejecta sheet. Using numerical simulations we develop a phase diagram
for this transition and show that the capillary number is the most appropriate order
parameter for the transition.