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Effect of flexibility on the shear-induced migration of short-chain polymers in parabolic channel flow

Published online by Cambridge University Press:  12 June 2006

DAVID SAINTILLAN
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
ERIC S. G. SHAQFEH
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA
ERIC DARVE
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA

Abstract

We use Brownian dynamics to investigate the effect of chain flexibility on the cross-streamline migration of short polymers in a pressure-driven flow between two infinite flat plates. A simulation method is described that models a polymer molecule at the Kuhn step level as a chain of $N$ freely jointed Brownian rods, and includes multibody hydrodynamic interactions between the chain segments and the surrounding channel walls. Our study confirms the existence of shear-induced migration away from the solid boundaries toward the channel centreline as a result of wall hydrodynamic interactions. At a fixed ratio $H/R_{g}$ of the channel width to the bulk radius of gyration, and at a fixed value of the Weissenberg number $Wi$, simulations show that migration is not significantly influenced by flexibility for chains of length $N\,{\ge}\, 2$. Much weaker migration is observed however for fully rigid chains ($N\,{=}\,1$), and a mechanism is discussed to explain migration in that case.

Type
Papers
Copyright
© 2006 Cambridge University Press

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