Extensional Flow of Wormlike Micellar Solutions
by Cromer, M.J., Cook, L.P. and McKinley, G.H.
We consider the inhomogeneous extensional response of a new constitutive model, the VCM model
[Vasquez, et al., 2007. A network scission model for wormlike micellar solutions I: model formulation
and homogeneous flow predictions. J. Non-Newt. Fluid Mech. 144, 122–139] that has been developed to
describe concentrated solutions of wormlike micelles.The time dependent numerical analysis is carried
out in a simplified slender filament formulation appropriate for transient elongational flows of complex
fluids. The simulations show that, beyond a critical extension rate, elongating filaments of a micellar fluid
described by the VCM model exhibit a dramatic and sudden rupture event as a resultof the scission of
the entangled wormlike chains. The computations capture many of the features of the high-speed rupture
process observed experimentally [Bhardwaj, et al., 2007. Filament stretching and capillary breakup extensional
rheometry measurements of viscoelastic wormlike micelle solutions. J. Rheol. 51, 693–719] in filament stretching
experiments with wormlike micelle solutions. The highly localized rupture predicted by the VCM model and the
corresponding evolution in the tensile force within the filament is contrasted with the familiar and more gradual
necking responses predicted by the upper convected Maxwelland Giesekus models under equivalent kinematic boundary conditions.