Contraction dynamics of viscoelastic filaments

Liquid filaments/ligaments---elongated drops---arise in diverse applications including ink-jet printing, 3D printing, crop spraying, and atomization coating. In these and other applications, whether such elongated drops retract back into a single drop or break up into multiple smaller droplets during contraction is a critical issue from a performance standpoint. Historically, there has existed a disconnect between computational and experimental studies of filament contraction. In computations, the fluid within filaments is taken to be quiescent at the initial instant t = 0. While doing so is expedient in simulations, it is nearly impossible to create a filament that is quiescent at t = 0 in experiments. Moreover, the working fluids in applications often contain performance-enhancing additives which render the fluids non-Newtonian. Here, we investigate the effect of adding polymer to a filament of an otherwise Newtonian fluid (solvent). Simulation results are reported that clarify the role of elastic stresses during contraction of viscoelastic filaments in situations in which the filament fluid at the initial instant is either quiescent or already in motion.