Liquid filaments, which are commonplace in daily life, nature, and technology, including inkjet printing and crop spraying, contract due to surface tension: they either retract into a single sphere or break up to produce a primary drop(s) and several smaller satellites. The latter are undesirable because they reduce printing quality and cause pollution due to spray drift. Surfactants and/or polymer additives can be used to control filament contraction and breakup. It has recently been demonstrated experimentally that the velocity at which the tips of contracting filaments retract can be increased in viscoelastic filaments that contain polymer additives compared to purely Newtonian filaments. Here, simulations are used to investigate the contraction of viscoelastic filaments whose rheology is described by the Oldroyd-B model. Filaments produced from nozzles are expected to be prestressed when they begin to contract. It is shown that the velocity with which the tips of prestressed filaments retract is greatly increased compared to filaments in which the polymer molecules are relaxed. This enhancement is explained by examining the value of $\mathit{\sigma }:\mathbf{D}$ ($\mathit{\sigma }$: Elastic stress; $\mathbf{D}$: Rate-of-strain tensor), which can be positive or negative. This quantity is positive when the flow does work on the polymer molecules but negative when the molecules do work on the flow, i.e., when elastic recoiling or unloading takes place. In prestressed filaments, elastic unloading takes place because $\mathit{\sigma }:\mathbf{D}<0$: The elastic stresses work by pulling the fluid in axially and pushing it out radially, thereby drastically increasing the tip velocity.

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• Drop & bubble phenomena
• Drops & bubbles
• Interfacial flows
• Filaments
• Non-Newtonian fluids
• Viscoelasticity