Study on drag reduction in turbulent boundary layer flow of heterogeneous surfactant solutions

本研究首先构建了表面活性剂溶液的槽式注入体系。其次，在壁面注入水或表面活性剂溶液的平板湍流边界层流动中进行流动可视化和LDV测量，以阐明减阻机理。结果表明，在注入表面活性剂溶液的情况下，沿流方向形成平行于壁面的层状结构，壁面附近的壁法向湍流被强烈减弱。此外，在均相和非均相（注入）表面活性剂溶液中，以摩擦速度为尺度的平均速度与减阻量排列良好，平均速度随减阻比的增加而增加。

In this study, first a slot injection system of surfactant solution was constructed. Next, the flow visualization and LDV measurements were performed in the flat-plate turbulent boundary layer flow with water or surfactant solution injection from the wall, in order to clarify the mechanism of drag reduction. It is found that in the case of surfactant solution injection, layered-structures parallel to the wall developed in the streamwise direction, and the wall-normal turbulence near the wall is strongly attenuated. Moreover, in both cases of homogeneous and heterogeneous (injected) surfactant solutions mean velocities scaled by the friction velocity are well arranged by the amount of the drag reduction, in which the mean velocity increases with the increase in the drag reduction ratio.