Effect of polymer–surfactant interaction on its turbulent drag reduction

Turbulent drag reduction (DR) efficacy of ionic poly(acrylic acid) and sodium dodecyl sulfate (SDS) complex system regarding polymer–surfactant interaction was examined under a turbulent flow in a rotating disk apparatus, in which the DR efficacy indicates how the torque is being reduced with a tiny amount of additives under a turbulent flow at a fixed rotational speed. Both addition of SDS and effect of pH on the ionic polymer were found to increase the polymer chain dimensions via a conformational structural change, thus enhancing the DR efficacy. Polymer–surfactant system also shows that there exists a critical polymer concentration at which the drag reduction becomes a maximum, and then above the critical concentration, the DR efficacy decreases more rapidly than that of pure polymeric systems. The dependence of drag reduction on the turbulent strength from the rotation speed change is also observed that the drag reduction increases with the increase of rotation speed regardless of polymer and surfactant concentration, implying that the complex interactions between the polymer and the surfactant molecules plays a critical role.

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► Turbulent drag reduction efficacy of PAA-SDS complex system was examined in a rotating disk apparatus.
► The DR efficacy induced by PAA-SDS complex is higher than that of pure PAA when the pH is fixed at 4.
► Highly extended PAA at intermediate PH shows more effective in the drag reduction.