Beads-on-string formation during filament pinch-off: Dynamics with the PTT model for non-affine motion (original) (raw)

2009, Journal of Non-newtonian Fluid Mechanics

Fundamental understanding of the formation and pinch-off of viscoelastic filaments is important in applications involving production of drops (e.g., ink-jet printing, micro-arraying, and atomization). In addition to delaying pinch-off, in some cases, viscoelasticity is known to cause the so-called beads-on-string structure, i.e., a number of small droplets interconnected by thin filaments. In a recent publication [H. Matallah, M.J. Banaai, K.S. Sujatha, M.F. Webster, J. Non-Newtonian Fluid Mech. 134 (2006) 77-104], it was shown that the simulation of an elongating filament modeled by the Phan-Thien/Tanner (PTT) equation with the Gordon-Schowalter (GS) convected derivative, which allows non-affine motion of polymer molecules in the continuum, results in the formation of the beads-on-string structure. On the other hand, such bead formation is not reported in calculations with other viscoelastic models that are also strain-hardening like the PTT model but do not have the GS convected derivative (see, e.g., [M. Yao, S.H. Spiegelberg, G.H. McKinley, J. Non-Newtonian Fluid Mech. 89 (2000) 1-43])