Mechanism of polymer drag reduction using a low-dimensional model

Anshuman Roy*, Alexander Morozov, Wim van Saarloos, Ronald G. Larson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Using a retarded-motion expansion to describe the polymer stress, we derive a low-dimensional model to understand the effects of polymer elasticity on the self-sustaining process that maintains the coherent wavy streamwise vortical structures underlying wall-bounded turbulence. Our analysis shows that at small Weissenberg numbers, Wi, elasticity enhances the coherent structures. At higher Wi, however, polymer stresses suppress the streamwise vortices (rolls) by calming down the instability of the streaks that regenerates the rolls. We show that this behavior can be attributed to the nonmonotonic dependence of the biaxial extensional viscosity on Wi, and identify it as the key rheological property controlling drag reduction.

Original languageEnglish
Article number234501
Number of pages4
JournalPhysical Review Letters
Volume97
Issue number23
DOIs
Publication statusPublished - 8 Dec 2006

Keywords

  • TURBULENT CHANNEL FLOW
  • SHEAR FLOWS
  • ADDITIVES
  • DYNAMICS

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