抄録
Our experimental studies on the turbulent characteristics of two-dimensional channel flows of drag-reducing surfactant solutions are described with keeping the accent on the visual studies on the coherent structures of near-wall turbulence, i.e. low-speed streaks, bursting phenomena and quasi-streamwise vortices. The hydrogen-bubble technique was widely used for the flow visualization. The results show that, with increasing drag reduction, DR, the mean spanwise streak spacing increases, the ejections become faint and the averaged ejection period increases, and the quasi-streamwise vortices diminish and the distance from the wall increases. It should be emphasized that the quasi-streamwise vortices were confirmed to be present even when DR was above 60%.
