Combined Brownian Dynamics and Spectral Simulation of the Recovery of Polymeric Fluids after Shear Flow
Received February 21, 1996 Revised Manuscript Received January 15, 1997 Abstract: The constrained recovery of polymeric fluids following cessation
of steady shear flow is
studied using linear bead-spring chain models for dilute polymer
solutions and the Curtiss-Bird model
for polymer melts. Brownian dynamics simulation techniques are
combined with a spectral method for
solution of the continuum equation of motion. The shear stress
required to solve the continuum equation
is computed directly from ensemble averages over internal
configurations of model molecules, thereby
eliminating the need for a closed-form constitutive equation.
Simultaneous solution of the equation of
motion for actual fluid velocities obviates the linear velocity profile
assumption used in previous studies
of constrained recoil. For each of the models examined in the
present work, a maximum was observed
in the overall recovery with increasing steady-state shear rate.
These maxima are an inherent consequence
of the polymer models' shear thinning behavior but are more pronounced
if the assumption of a linear
velocity profile is relaxed.
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