Journal
AICHE JOURNAL
Volume 60, Issue 4, Pages 1460-1475Publisher
WILEY
DOI: 10.1002/aic.14328
Keywords
turbulence; complex fluids; fluid mechanics
Categories
Funding
- National Science Foundation [CBET-1066223]
- MDG
- Air Force Office of Scientific Research [FA9550-11-1-0094]
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1066223] Funding Source: National Science Foundation
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Direct numerical simulations and statistical analysis techniques are used to study the drag-reducing effect of polymer additives on turbulent channel flow in minimal domains. Additionally, a new formulation of Karhunen-Loeve decomposition for viscoelastic flows is introduced, allowing the dominant features of the polymer stress fields to be characterized. In minimal channels, there are intervals of active and hibernating turbulence that display very different structural and energetic characteristics; the present work illustrates how the statistics of these intervals evolve over the entire range of drag reduction (DR) levels. The effect of viscoelasticity on minimal channel turbulence is twofold: first, it strongly suppresses the active turbulent dynamics that predominate in Newtonian flow and second, at sufficiently high Weissenberg number it stabilizes the dynamics of hibernating turbulence, allowing it to predominate in the maximum drag reduction regime. In this regime, the stress fluctuations become delocalized from the wall region, encompassing the entire flow domain. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 1460-1475, 2014
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