A phase diagram of the pinch-off-type behavior of impulsively-induced viscoelastic liquid jets

Abstract

In this study, we systematically investigate the jet behaviors of viscoelastic liquids, focusing on the region of high velocity and high viscoelasticity, which has not been investigated in previous studies. We generate viscoelastic jets using an impulsive force and categorize the resulting jets into two types: pinch-off jets (jets that break up during elongation after ejection) and no-pinch-off jets (jets that pull back to the nozzle after maximum elongation or jets that return without elongation after ejection). We then propose criteria to characterize these regions using the Weissenberg number and the Reynolds number, which are dimensionless numbers composed of the rheological properties of the solution and the initial conditions of the jet injection. It is found that pinch-off jets occur at Re ≳ 23.4Wi in regions of high elasticity Wi ≳ 10, and at Re ≳ 250 in regions of low elasticity Wi ≲ 10. We also show that the phase diagram can be explained by modeling a focused jet using the finitely extensible non-linear elastic dumbbell model with the Chilcott–Rallison closure approximation (FENE-CR).