Europhys. Lett.
Volume 68, Number 6, December 2004
Page(s) 825 - 831
Section Electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics
Published online 17 November 2004
Europhys. Lett., 68 (6), pp. 825-831 (2004)
DOI: 10.1209/epl/i2004-10282-6

Saturation of turbulent drag reduction in dilute polymer solutions

R. Benzi1, V. S. L'vov2, I. Procaccia2 and V. Tiberkevich2

1  Dipartimento di Fisica and INFM, Università "Tor Vergata" Via della Ricerca Scientifica 1, I-00133 Roma, Italy
2  Department of Chemical Physics, The Weizmann Institute of Science Rehovot, 76100 Israel

received 15 June 2004; accepted in final form 15 October 2004
published online 17 November 2004

Drag reduction by polymers in turbulent wall-bounded flows exhibits universal and non-universal aspects. The universal maximal mean-velocity profile was explained in a recent theory. The saturation of this profile and the crossover back to the Newtonian plug are non-universal, depending on Reynolds number ${\mathcal R}e$, concentration of polymer $c_{\ab{p}}$ and the degree of polymerization $N_{\ab{p}}$. We explain the mechanism of saturation stemming from the finiteness of extensibility of the polymers, predict its dependence on $c_{\ab{p}}$ and N in the limit of small $c_{\ab{p}}$ and large ${\mathcal R}e$, and present the excellent comparison of our predictions to experiments on drag reduction by DNA.

47.27.-i - Turbulent flows, convection, and heat transfer.
47.27.Ak - Fundamentals.
47.27.Nz - Boundary layer and shear turbulence.

© EDP Sciences 2004