2012 Volume 40 Issue 2 Pages 85-90
Experimental study on the relaxation behavior of the drag-reducing surfactant solution has been performed in order to investigate the mechanism of the drag reduction occurrence. The relaxation times and the drag reduction rates were measured in a wide range of the surfactant concentration and of the molar ratio of the counter-ions to surfactants. From the results, it was found that the present surfactant solution has at most three relaxation times in a middle range of the surfactant concentration and of the molar ratio. It was also found that the drag reduction occurs when the shortest relaxation time of 0.1 s exists. Thus, it was concluded that the existence of the shear-induced structure having this shortest relaxation time is important for the drag reduction occurrence.
