Dynamics Of Liquid Filament In Various Fluids

When a liquid jet issues from a nozzle and discharges into another fluid, it becomes unstable and breaks into droplets. Beside the various industrial applications, process of drop formation itself is also a fascinating and formidable free boundary problem. The breakup of liquid filaments was studied computationally and experimentally.The beads-on-string structure was a well-known phenomenon for viscoelastic jets. As a remark, it was simulated for a Newtonian fluid. The theoretical framework of the one-dimensional (1-D) long-wave theory of the slender jet was used. The droplet dynamics on the filament-bead structure and velocity profiles at various times were analyzed. These phenomena included drop migration and draining. The capillary number was inversely proportional to the surface tension. As the capillary number increased, the droplet underwent transient deformations until it eventually collapsed into smaller fragments. As the capillary number continued to increase, the surface tension was not strong enough to squeeze the filament and create a satellite drop. Instead, the main drops were compressed and the jet collapse may transfer surface tension energy to kinetic energy and set the drop into motion. The gravity was taken into consideration to see the capillary jet instability. The capillary jet instability under the influence of gravity has been simulated to show the evolution of gravity-stretching.Many numerical simulations on the dynamics of the filament-bead structure for elastic fluids were performed using Oldroyd-B model. The computed results agreed with the well-known phenomenon that a non-Newtonian jet broke up much more slowly than a Newtonian one. The slower breakup process of elastic non-Newtonian fluid jet provided sufficient time for fluid to exhibit some interesting phenomena such as drop drainage and migration. The forces in the filament stretching could be approximated by the summation of the most important terms. The elastic force played an important role in the elastic jet dynamics. It significantly retarded the evolution of...