Peter Wapperom and Roland Keunings
Impact of decoupling approximation between
stretch and orientation in rheometrical and complex flow
of entangled linear polymers
Journal of Non-Newtonian Fluid Mechanics 122 (2004) 33-43
Abstract
We study the rheometrical and complex flow response of the
coupled version of the double-convection-reptation model with chain
stretch. This model for monodisperse entangled linear polymers has
recently been proposed by Marrucci and Ianniruberto
[Phil. Trans. Roy. Soc. A, 361 (2003) 677--688] to overcome the
anomalous shear thickening that was present in an earlier version of
the theory. It avoids the decoupling approximation between orientation
and stretch. Except for the shear thickening, both coupled and
decoupled
models show very similar results that are in qualitative agreement with
available rheometrical data for two nearly monodisperse polymer
solutions. In contraction/expansion flow simulations, however, higher
Weissenberg numbers can be attained with the coupled model. Simulations
in the stretch-dominated regime predict a dramatic growth of the
upstream vortex activity and an increase of the pressure correction.
Keywords
tube model; chain stretch; decoupling approximation; numerical simulation