Mechanistic study of drag reduction in turbulent pipeline flow over anionic polymer and surfactant mixtures

The mixed aqueous solutions of anionic surfactant sodium dodecyl sulfate with polymer polyacrylamide of various kinds, i.e., cationic, anionic, nonionic, and zwitterion, were firstly tested to study their synergistic effect on drag reduction performance. The optimal combination of sodium dodecyl sulfate with anionic polyacrylamide was confirmed due to their strong hydrophobic interaction and electrostatic repulsion caused by the same charge. The surface tension, conductivity, and viscosity of pure surfactant solution and mixed solutions at different surfactant concentrations with anionic polymer of certain concentration were tested, and their drag reduction behavior in pipe flow was also investigated experimentally. It turns out that drag reduction performance acquired from the combination of anionic surfactant and anionic polyacrylamide is better than either of the single additive, especially under high shear rate. For the mixtures, the degree of drag reduction is strongly dependent on the concentration of SDS and more pronounced in the high Reynolds number range. The best drag reduction performance is obtained for the SDS concentration around the polymer saturation point. Our work should be of value for the drag reduction in the application such as shale gas fracturing and various fluid transports.