title: Concentration effects on turbulence in dilute polymer solutions far from walls.
abstract: We report measurements of the modification of turbulence far from any walls by small concentrations of long-chain polymers. We consider a range of statistical properties of the flow, including Eulerian and Lagrangian velocity structure functions, Eulerian acceleration correlation functions, and the relative dispersion of particle pairs. In all cases, we find that the polymer concentration has a strong effect on the extent to which the statistical properties are changed compared to their values in pure water. These effects can be captured by the recently proposed energy flux-balance model (when suitably extended into the time domain for Lagrangian statistics). However, unlike previous measurements, which found that the concentration effect could be completely scaled out, we consistently find that our data collapse onto two different master curves, one for small concentration and one for larger concentration. We suggest that the difference between the two may be related to the onset of interactions among polymer chains, which is likely to be more easily observed at the small Weissenberg numbers we consider here.
authors.affiliation: Department of Mechanical Engineering & Materials Science, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Alexandre
authors.initials: A
authors.lastname: de Chaumont Quitry
authors.affiliation: Department of Mechanical Engineering & Materials Science, Yale University, New Haven, Connecticut 06520, USA.|Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Ouellette