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An improved diameter scaling correlation for turbulent flow of drag-reducing polymer solutions

Summary: An improved diameter scaling correlation for turbulent
flow of drag-reducing polymer solutions
K. Gasljevic, G. Aguilar, E.F. Matthys
Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, CA 93106, USA
Received 18 December 1997; received in revised form 10 September 1998
The friction coefficient was measured for developed flow of drag-reducing polymer solutions in tubes of 2, 5, 10, 20 and
52 mm i.d. Our results were processed along with other authors' data in terms of different parameters in order to investigate
the possibility of developing a simple empirical method for the prediction of the pipe diameter effect on friction. We found
that the drag-reduction coefficient (DR), if expressed as a function of the fluid bulk velocity (V), becomes independent of the
tube diameter in the subcritical region (i.e. without fluid degradation), with the deviations being smaller than about 5% for all
the diameters and velocities covered. This correlation proved to be not only better than similar procedures based on friction
velocity, but also more convenient and physically more meaningful. It was also found that the logarithmic layer shift in the 3-
layers velocity profile is also better correlated with the bulk velocity than with the friction velocity. Finally, existing models for
drag-reduction involving non-dimensional correlations between the integral flow parameters and the fluid properties were also
reevaluated in light of these findings. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Drag-reduction; Diameter effect; Turbulent flow; Polymer solutions; Scaling
1. Introduction
For turbulent flow of Newtonian fluids through smooth circular tubes, the friction coefficient or wall
shear stress is a function of the Reynolds number only. For drag-reducing fluids in the non-asymptotic


Source: Aguilar, Guillermo - Department of Mechanical Engineering, University of California at Riverside


Collections: Engineering