  The dynamics of ligaments retracting under the action of surface tension
occurs in a multitude of natural and industrial applications, such as inkjet
printing and atomisation. We perform fully three-dimensional, two-phase direct
numerical simulations of the retraction dynamics with soluble surfactants. A
full parametric study is performed using a hybrid interface-tracking/level-set
method, which is utilised to treat the interface; this method is capable of
capturing faithfully the topological transitions that are a feature of the flow
over a certain range of ligament aspect ratios and Ohnesorge numbers. Our
results demonstrate the delicate interplay between capillarity, modulated by
the presence of surfactants, surfactant-induced Marangoni stresses, inertial
and viscous effects. Particular attention is paid to the formation of vortices,
which accompany the retraction process, and the influence of surfactant on the
vortex dynamics.
