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Polymer stress tensor in turbulent shear flows.
MedLine Citation:
PMID:  15697720     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The interaction of polymers with turbulent shear flows is examined. We focus on the structure of the elastic stress tensor, which is proportional to the polymer conformation tensor. We examine this object in turbulent flows of increasing complexity. First is isotropic turbulence, then anisotropic (but homogenous) shear turbulence, and finally wall bounded turbulence. The main result of this paper is that for all these flows the polymer stress tensor attains a universal structure in the limit of large Deborah number De >> 1. We present analytic results for the suppression of the coil-stretch transition at large Deborah numbers. Above the transition the turbulent velocity fluctuations are strongly correlated with the polymer's elongation: there appear high-quality "hydroelastic" waves in which turbulent kinetic energy turns into polymer potential energy and vice versa. These waves determine the trace of the elastic stress tensor but practically do not modify its universal structure. We demonstrate that the influence of the polymers on the balance of energy and momentum can be accurately described by an effective polymer viscosity that is proportional to the cross-stream component of the elastic stress tensor. This component is smaller than the streamwise component by a factor proportional to De2. Finally we tie our results to wall bounded turbulence and clarify some puzzling facts observed in the problem of drag reduction by polymers.
Authors:
Victor S L'vov; Anna Pomyalov; Itamar Procaccia; Vasil Tiberkevich
Publication Detail:
Type:  Journal Article     Date:  2005-01-11
Journal Detail:
Title:  Physical review. E, Statistical, nonlinear, and soft matter physics     Volume:  71     ISSN:  1539-3755     ISO Abbreviation:  Phys Rev E Stat Nonlin Soft Matter Phys     Publication Date:  2005 Jan 
Date Detail:
Created Date:  2005-02-08     Completed Date:  2005-05-19     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101136452     Medline TA:  Phys Rev E Stat Nonlin Soft Matter Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  016305     Citation Subset:  -    
Affiliation:
Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel.
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