Effects of Drag-reducing Additives on Vortex Stretching

Abstract

Giles and Pettit¹ have shown that, in tubes of small diameters, solutions of additives which reduce turbulent drag can apparently maintain laminar flow at Reynolds numbers greatly above the limit of about 2,000, which for water usually marks the onset of turbulent flow. The friction factor rises above the Hagen–Poiseuille line, however, and Giles and Pettit attribute this to a shear-thickening of the fluid, and suggest that the viscosity of the additive solution effectively increases at sufficiently high shear rates.