Dynamics of Bead Formation, Filament Thinning, and Breakup in Weakly Viscoelastic Jets
By A. M. Ardekani, V. Sharma, G. H. McKinley
The
spatiotemporal evolution of a viscoelastic jet depends on the relative
magnitude of capillary, viscous, inertial and elastic stresses. The
interplay of capillary and elastic
stresses leads to formation of
very thin and stable filaments between drops, or to ‘beadson-a-string’
structure.We show that by understanding the physical processes that
control
different stages of the jet evolution it is possible to
extract transient extensional viscosity information even for very low
viscosity and weakly-elastic liquids which is a particular
challenge
using traditional rheometers. The parameter-space at which a forced jet
can be used as an extensional rheometer is numerically investigated
using a one-dimensional
nonlinear free surface theory for Oldroyd-B
and Giesekus fluids. The results show that even when the ratio of
viscous to inertio-capillary time scales (or Ohnesorge number) is
as low as Oh ∼ 0.02, the temporal evolution of the jet can be used to obtain elongational properties of the liquid.