Abstract / Description of output
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 language | English |
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Article number | 234501 |
Number of pages | 4 |
Journal | Physical Review Letters |
Volume | 97 |
Issue number | 23 |
DOIs | |
Publication status | Published - 8 Dec 2006 |
Keywords / Materials (for Non-textual outputs)
- TURBULENT CHANNEL FLOW
- SHEAR FLOWS
- ADDITIVES
- DYNAMICS