Volume 100, Number 2, October 2012
|Number of page(s)||5|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||30 October 2012|
Onset and universality of turbulent drag reduction in von Karman swirling flow
Department of Physics of Complex Systems, Weizmann Institute of Science - Rehovot 76100, Israel
Received: 6 September 2012
Accepted: 21 September 2012
We report the results of experiments on turbulent drag reduction (TDR) in swirling flow of water and water-sucrose polymer solutions, where Re and Wi as well as polymer concentration ϕ are varied. The friction coefficients Cf and Cp defined through average torque and rms of pressure fluctuations prms for different elasticity El = Wi/Re and ϕ vs. Re/Rec collapse onto universal curves in accord with theory, where Rec is Re at TDR onset. The transition lines to the TDR state, Rec − El and Rec − ϕ, are measured and relevant physics is discussed. Power spectra for Γ and p at Re/Rec > 1 show a drastic reduction of low-frequency noise and the emergence of a peak corresponding to the main vortex frequency in accord with TDR.
PACS: 47.50.-d – Non-Newtonian fluid flows / 47.27.Jv – High-Reynolds-number turbulence / 47.57.Ng – Polymers and polymer solutions
© EPLA, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.