Abstract
Abstract 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.
Highlights
In pipe or channel flows, a great part of the energy loss is caused by skin friction
Comparing the curves for cetyltrimethyl ammonium chloride (CTAC) solutions in the smooth channel with that in the grooved channel, we find that the drag reduction effectiveness of surfactant solutions in the smooth channel is better than that in the grooved one for 50 ppm; it is just the opposite for 70-150 ppm CTAC solutions
For the grooves used in this study, the optimal concentration of surfactant is 70 ppm, the drag-reducing effect of which is enhanced by grooves by 5% on the basis of drag-reducing surfactant solution
Summary
In pipe or channel flows, a great part of the energy loss is caused by skin friction. Rehage et al (1986) reported that the apparent viscosity of dilute surfactant solutions increased significantly by increasing shear stress This phenomenon was called a shearthickening transition, resulting from the formation of shear-induced structures (SIS). Kawaguchi et al (2002) performed a study on the spatial structure of turbulence by PIV They found that the formation of a turbulent vortex was inhibited and that the scale of the vortex became larger when the surfactant was added to water. This suggested that a turbulent environment with a relatively larger vortex was obtained and provided an excellent condition for application of other drag-reducing methods related to the scale of the turbulent vortex. Hadri et al (2011) discovered that the interaction between the surfactant chains and the turbulent structure was related to the temperature and concentration, namely, only in a certain range of temperature and concentration could the surfactants suppress turbulent vortices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
