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

The friction coefficient was measured for developed flow of drag-reducing p olymer solutions in tubes of 2, 5, 10, 20 and 52 mm i.d. Our results were p rocessed along with other authors' data in terms of different parameters in order to investigate the possibility of developing a simple empirical meth od for the prediction of the pipe diameter effect on friction. We found tha t the drag-reduction coefficient (DR), if expressed as a function of the fl uid bulk velocity (V), becomes independent of the tube diameter in the subc ritical region (i.e. without fluid degradation), with the deviations being smaller than about 5% for all the diameters and velocities covered. This co rrelation proved to be not only better than similar procedures based on fri ction velocity, but also more convenient and physically more meaningful. It was also found that the logarithmic layer shift in the 3-layers velocity p rofile is also better correlated with the bulk velocity than with the frict ion velocity. Finally, existing models for drag-reduction involving non-dim ensional correlations between the integral flow parameters and the fluid pr operties were also reevaluated in light of these findings. (C) 1999 Elsevie r Science B.V. All rights reserved.