Abstract:  In order to clarify the drag-reducing mechanism of turbulent through adding surface active agent to pure water, after examining previous investigations, it is indicated that the substantial decrease of Reynolds shear stress is due to the effects of decorrelation caused by adding surfactant. From a balance analysis on time-average energy and turbulent energy in an enclosed two-dimensional rectangle flume flow with weak Reynolds shear stress, added micelle shear stress plays a key role in the forming and maintaining the turbulent flow for drag-reducing surfactant solution. Furthermore, the bigger the micelle fluctuating energy taken from total mean flow, the smaller the drag-reduction rates are. For the two dimensional open flume, through analyzing the turbulent energy spectrum of drag-reducing surfactant solution measured by a two dimensional laser Doppler current-meter, large scale vortices contain more energy than that of Newtonian fluid. Conversely, small vortices contain less energy, and the scale of energy dissipation is increased. This is the basic characteristics of the energy transporting in a surfactant solution drag-reducing flow.

Key words:  surfactant  ,  drag-reduction  ,   Reynolds shear stress  ,   turbulent energy-transporting ,    micelle