Abstract
Drag reduction of turbulent flow by surfactant solutions is well known. However, most of studies about it have been carried out using homogeneously premixed solutions. In this study, drag reduction by injection of dense surfactant solution into a turbulent pipe flow has been studied. As a result, it is found that higher drag reduction is obtained by injection of dense surfactant solutions than that of homogeneously premixed solutions. It may be important for drag reduction by injection that surfactant solutions mix considerably with main flow.
