Reynolds number dependence of drag reduction by rodlike polymers

Abstract

Reynolds number dependence of drag reduction by rodlike polymersAmarouchene, Y.; Bonn, D.; Kellay, H.; Lo, T.-S.; L'vov, V.S.; Procaccia, I. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We present experimental and theoretical results addressing the Reynolds number ͑Re͒ dependence of drag reduction by sufficiently large concentrations of rodlike polymers in turbulent wall-bounded flows. It is shown that when Re is small the drag is enhanced. On the other hand, when Re increases, the drag is reduced and eventually, the maximal drag reduction asymptote is attained. The theory is shown to be in agreement with experiments, explaining the universal and rationalizing some of the the nonuniversal aspects of drag reduction by rodlike polymers. Download date: 12 May 2018 Reynolds number dependence of drag reduction by rodlike polymers

Turbulent Drag Reduction by Biopolymers in Large Scale Pipes

“…A different behavior is observed only for the largest concentration tested, 0.2% XG, where the measured specific pressure drop is larger than for tap water. Drag enhancement at large polymer concentration and small Reynolds number has been already observed for rigid polymers [27,28] and attributed to the homogeneous increase of effective viscosity of the fluid which prevails over the reduction of momentum flux to the wall. At larger Reynolds number, i.e., for velocity values in the range U ¼ (1-3 m/s), the measured specific pressure drop for XG solutions is always less than in tap water.…”

Colloquium: Theory of drag reduction by polymers in wall-bounded turbulence

“…16, and the qualitative agreement with the experimental observations is obvious. Another interesting comparison with experimental findings is available due the work presented in (Amarouchene et al, 2007) where the percentage of drag enhancement and reduction were measure as a function of ν p . The quantitative comparison needs a careful identification of the material parameters in the theory and the experiment, and this was described in detail in (Amarouchene et al, 2007).…”

Enhancement of mixing by rodlike polymers

“…The parameter η p determines the coupling between the polymer phase and the fluid and is an increasing function of the polymer concentration. The values of η p considered here (η p 5) correspond to a dilute solution [4,8]. The above polymer model was studied extensively in the turbulent-drag-reduction regime at high Reynolds number [9].…”