Unexpected Dynamics of Dumbbell-Shaped Filaments

Numerous approaches exist for producing drops which are useful in applications as diverse as printing, coating, and spraying. One approach relies on low-speed drop formation, which is common to DOD ink jet printing and dripping. Another approach exploits the instability of jets. Yet a third approach relies on creation of liquid sheets which subsequently disintegrate into ligaments. In all of these approaches, the occurrence and the subsequent breakup of long, slender filaments into drops are commonplace. In this talk, the recoil dynamics of initially quiescent, dumbbell-shaped liquid filaments surrounded by air are analyzed by 1D numerical simulation using the slender-jet approximation. Special attention is paid to the stability of the dumbbell shaped filaments in terms of the governing dimensionless groups, e.g. initial aspect ratio, dumbbell size and asymmetry, and Ohnesorge number. The results obtained with the 1D code are confirmed by direct comparison against predictions made with a 3D but axisymmetric free surface solver. The fate of recoiling dumbbell-shaped filaments is summarized by a phase diagram.