Experimental study on the collaborative drag reduction performance of a surfactant solution in grooved channels

Turbulence with a relatively larger vortex is obtained in drag-reducing surfactant solution, which provides an excellent condition for the application of small scale grooves. In this work, the coupling drag reduction performance of surfactant solution and grooves was experimentally investigated to explore the complementary possibility between their drag reduction mechanisms. The cationic surfactant cetyltrimethyl ammonium chloride (CTAC) mixed with the counterion salt sodium salicylate (NaSal) was experimented in smooth or grooved channel, respectively, at the mass concentrations of 50-150 ppm. It was found that the surfactant solutions gave more effective drag reduction in the grooved channel by the interaction between the "restriction effect" and "peak effect" of grooves. Moreover, the critical temperature and critical Reynolds number of the surfactant solution were smaller in the grooved channel, and the friction factor in the grooved channel increased much more rapidly than that in the smooth channel when Re is larger than a critical value.