ID 223

Viscoelastic ligament dynamics in free liquid jet experiments

 

Abstract:

The main experimental methods to determine the relaxation time of a viscoelastic liquid are based on the liquid ligament thinning measurement. In the case of a CaBER (Capillary Breakup Extensional Rheometer), a stretched liquid bridge is formed between two plates and its diameter temporal evolution allows a measurement for the relaxation time. This technique shows difficulties for dilute polymer solutions due to the very fast thinning of the liquid filament. To overcome this difficulty, another experimental technique, the ROJER (Rayleigh Ohnesorge Jetting Extensional Rheometer), has been developed based on liquid jet breakup. The atomization of a viscoelastic liquid jet presents typical beads-on-a-string morphologies, where spherical drops are linked by cylindrical threads for which the thread thinning allows a measurement for the relaxation time. However, this method reveals that the relaxation time measurement depends on different operating parameters such as the jet velocity or the initial perturbation amplitude. Following previous works of the team, we present here a multi-scale analysis of viscoelastic ligament dynamics in free falling jet experiments, for which jet velocity and nozzle sizes are varied. The goal of this study is to define optimal operating conditions to measure the relaxation time in a liquid jet experiment.