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

在本研究中，首先建立了表面活性剂溶液的狭缝注入系统。其次，在平板湍流边界层流动与水或表面活性剂溶液从壁面喷射的流动显示和LDV测量，以澄清减阻的机制。结果表明，在表面活性剂溶液注入的情况下，平行于壁面的层状结构沿流向发展，壁面附近的壁面法向湍流强烈衰减。此外，在这两种情况下的均匀和非均匀（注入）的表面活性剂溶液的平均速度缩放的摩擦速度以及安排的减阻量，其中的平均速度增加的减阻比的增加。

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.