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|
Saturation of turbulent drag reduction in dilute polymer solutions
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
Accepted: 15 October 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 , concentration of polymer and the degree of polymerization . We explain the mechanism of saturation stemming from the finiteness of extensibility of the polymers, predict its dependence on and N in the limit of small and large , and present the excellent comparison of our predictions to experiments on drag reduction by DNA.
PACS: 47.27.-i – Turbulent flows, convection, and heat transfer / 47.27.Ak – Fundamentals / 47.27.Nz – Boundary layer and shear turbulence
© EDP Sciences, 2004
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