Contraction velocity of viscoelastic filaments

Liquid filaments/ligaments---elongated drops---are omnipresent in diverse applications, including ink-jet printing, crop spraying, and atomization coating. In these and other applications, the working fluids often contain polymer additives which render the fluids non-Newtonian. Motivated by the fact that in experiments and applications the filament is often highly stretched axially at the initial instant when it is just beginning to contract, the effect of a nonzero initial stress condition is examined on the retraction of axisymmetric viscoelastic (VE) filaments described by the Oldroyd-B model. Among others, a feature of great practical and fundamental importance in all filament retraction processes is the filament's contraction velocity. Here, we compare the contraction velocity of VE filaments to that of Newtonian ones and show that initially pre-stressed VE filaments experience unexpectedly large accelerations during recoil. Simulation results are probed to furnish a physically-based explanation as to how the initial pre-stressing can result in such large accelerations and hence increased contraction velocities.