Turbulent characteristics of ctab surfactant solution flows in turbulent boundary layers

In order to clarify the drag-reducing mechanismwith a surfactant solution, the turbulent chara-cteristics of CTABsurfactant solution flow for a zero-pressure gradient boundary layer on flatplates is investigated by using a two dimensional LDV system. The resultsobtained are found as follows compared with the corresponding statistics forwater flow. The viscous sublayer for the surfactant solution is thicker thanthat for water flow. The mean streamwise velocity profile falls betweenthose of laminar and turbulent velocity profiles in Newtonian fluid flow.The peak of the streamwise turbulence intensity is smaller than that forwater, the location where it appears is further away from the wall and thesecond peak appears near the center of the boundary layer. The wall-normalturbulence intensity is greatly suppressed and the Reynolds shear stress isalmost zero throughout the boundary layer, which shows that the surfactantsolution can weaken the correlation between the two components of velocityfluctuation, thus, it can reduce the production of turbulent kinetic energyso that the driven power for transporting fluids can be saved.