Matched asymptotic solutions for the steady banded flow of the diffusive Johnson-Segalman model in various geometries

We present analytic solutions for steady flow of the Johnson-Segalman (JS) model with a diffusion term in various geometries and under controlled strain rate conditions, using matched asymptotic expansions. The diffusion term represents a singular perturbation that lifts the continuous degeneracy of stable, banded, steady states present in the absence of diffusion. We show that the stable steady flow solutions in Poiseuille and cylindrical Couette geometries always have two bands. For Couette flow and small curvature, two different banded solutions are possible, differing by the spatial sequence of the two bands. (C) 2000 Elsevier Science B.V. All rights reserved.