Thread-like micelles of cationic surfactant aggregate to SIS (Shear-induced structure), and the SISs are seems to attribute to drag reduction effect. In this study, we experimentally investigated drag-reducing flow using cationic surfactant solutions. The SISs were visualized in turbulent flow to elucidate the induced mechanism and role of a micelle structure in drag reduction. The streamwise changes in the SISs and the drag reduction were measured and their relationship was discussed. In our experiments, the SISs were generated from a wall and had gel-like characteristics. The number and thickness of SISs increased downstream, and this increase was correlated with the streamwise increase in the drag reduction rate
