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Simulated polymer stretch in a turbulent flow using Brownian dynamics

Published online by Cambridge University Press:  16 April 2004

V. E. TERRAPON
Affiliation:
Mechanical Engineering Department, Stanford University, Stanford, CA 94305, USA
Y. DUBIEF
Affiliation:
Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA
P. MOIN
Affiliation:
Mechanical Engineering Department, Stanford University, Stanford, CA 94305, USA Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA
E. S. G. SHAQFEH
Affiliation:
Mechanical Engineering Department, Stanford University, Stanford, CA 94305, USA Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
S. K. LELE
Affiliation:
Mechanical Engineering Department, Stanford University, Stanford, CA 94305, USA

Abstract

We examine the phenomenon of polymer drag reduction in a turbulent flow through Brownian dynamics simulations. The dynamics of a large number of single polymer chains along their trajectories is investigated in a Newtonian turbulent channel flow. In particular, the FENE, FENE-P and multimode FENE models with realistic parameters are used to investigate the mechanisms of polymer stretching. A topological methodology is applied to characterize the ability of the flow to stretch the polymers. It is found using conditional statistics that at moderate Weissenberg number Wi the polymers, that are stretched to a large fraction of their maximum extensibility, have experienced a strong biaxial extensional flow. When Wi is increased other flow types can stretch the polymers but the few highly extended molecules again have, on average, experienced a biaxial extensional flow. Moreover, highly extended polymers are found in the near-wall regions around the quasi-streamwise vortices, essentially in regions of strong biaxial extensional flow.

Type
Papers
Copyright
© 2004 Cambridge University Press

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