Abstract
Turbulent drag reduction due to surfactant solutions was investigated for a small-scale pipeline system composed complex elements. The effects of the counter-ion concentration were discussed on the drag reduction, the viscoelastic characteristics, and the vortex inhibition. When the molar concentration of the counter-ion was ten times higher than that of the surfactant, the drag reduction appeared over the wide range of the surfactant concentrations. The combination of this counter-ion concentration and dilute surfactant exhibited the modest increase in viscosity and the vortex inhibition at high stretching rate.
