Turbulent drag reduction polymeric solutions

Abstract

The paper presents the results of a comprehensive analytical and experimental program on the effect of additives, mainly long-chain molecules, on drag reduction in turbulent flow of aqueous polymeric solutions. The intent of the study was to develop a basic understanding, deduced from the experimental observations, of the underlying physical mechanism responsible for the phenomenon. The paper assumes that the turbulent drag reduction of solutions of high-polymers is due to the damping of turbulent fluctuations by the interspersed polymers, thereby suppressing the generation of turbulence in the viscous sublayer of the flow. Transition itself would also be restrained at sufficiently great polymer concentrations. The basic experiment is the measurement of the friction factor versus Reynolds number for flow in a pipe for various concentrations of a given polymer dissolved in water. The experimental data on drag reduction are interpreted in terms of additive concentration, pipe diameter, and a hydraulic damping thickness analogous to the hydraulic roughness of rough surfaces. Formulas are accordingly derived for velocity profile and friction factor. ( Author )