Use of Pipe Flow Correlations to Predict Turbulent Skin Friction for Drag-Reducing Fluids

Abstract

Experimental data are used to determine the effective limits of the Meyer correlation for interpreting turbulent pipe flow experiments with drag-reducing additives. Definition of these limits is necessary in order to design pipe flow experiments suitable for measuring the universal drag-reducing properties of these fluids. Data from various sources for 10 different pipe sizes are used in the study. The results show that the correlation is suitable for generalization if the ratio of the velocity profile shift function AB to the dimensionless pipe radius VR is greater than 0.033. This specifies a minimum pipe size to be used for a given additive solution to obtain results which can be generalized. This minimum pipe diameter effect, first suggested by Granville, can be used to explain anomalous drag reduction measurements in small pipes and thin boundary layers. The results of this study also suggest that degradation of the additive solution occurs in single-pass pipe flow systems at a given friction velocity for a particular solution, independent of pipe length. In addition, degradation occurs in poly(ethylene oxide) solutions at about the same value of friction velocity as in acrylamide copolymers. The basic correlation is suitable for the solutions studied up to a friction velocity of about 1 fps, when degradation occurs.