Abstract
It is known that frictional drag in turbulent flow can be reduced considerably by adding a small amount of surfactant to the fluid. In order to investigate the mechanism of this phenomenon, the turbulent characteristics in surfactant aqueous solution flow in a planer two-dimensional channel has been investigated through visualization by dye injection, velocity measurements by LDV and time scale measurements through temperature fluctuation. Analysis of velocity fluctuation showed that Reynolds shear stress and turbulence production is diminished in drag reducing flow. Coherent structure was not obvious in this flow. It was observed that integral time scale become large near the wall. This finding suggests smaller dissipation and weakening of cascade process of turbulence energy. Lower turbulent diffusion can be explained by these characteristics found in drag reducing flow.
