Instabilities and complex time dependence are often associated with wall slip in polymer-melt flows. We present here a phenomenological slip model that takes into account the unsteady-state kinetics of the wall-polymer interactions. In this model, both the shear and normal stresses arise, in contrast to other models used in stability analyses of shear flow, which incorporate only shear stresses and yield only stable flow. Asymptotic analysis of viscoelastic shear flow with this slip model predicts instability with respect to short wavelength fluctuations at sufficiently high shear rates, showing that slip can lead to instability in viscoelastic shear flow.

• Received 12 March 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.956