Control of Both Ionic Properties and Micellar Structure for Enhanced Turbulent Drag Reduction Performance of Surfactant Solutions

Surfactants with various ionic properties have been broadly employed as assisting or main additives for fluid drag reduction. However, how the micellar structure of surfactants affects their turbulence drag reduction performance has not been systematically investigated, and the underlying mechanism remains unclear. In this study, we present a systematic experimental investigation of the turbulent drag reduction performance of surfactants with head groups of different ionic properties in a circular tube. By controlling such fluid parameters as surfactant ionic properties and concentration, flow time, turbulence intensity, and pH value, we were able to obtain surfactant solutions of various micellar structures, which make it possible to investigate the underlying mechanism between microscale assembly morphology and the resulting drag reduction performance of surfactants under turbulence conditions. Overall, the zwitterionic surfactant BS-12 has the best drag reduction performance, followed by the anionic surfactant sodium dioctyl sulfosuccinate and the nonionic surfactant polyoxyethylene lauryl ether, and finally the cationic surfactant hexadecyltrimethylammonium chloride. The spreading characteristics of the different types of surfactant solutions on a metal plate were experimentally investigated, and the spreading coefficient is positively correlated with turbulent drag reduction rate induced by the surfactant. The mechanism of turbulent drag reduction induced by surfactants with different ionic properties has been explored, and it turns out that the micelle structure formed by surfactants is the main cause of turbulent drag reduction. The increase in the supermolecular structure size of the surfactant molecules in solution is beneficial in improving its turbulent drag reduction performance.