Behavior of the Hairpin Votex in a Laminar Boundary Layr of Surfactant Solution

为了阐明表面活性剂溶液湍流减阻的机理，对层流平板边界层中连续涡和孤立涡中的Hairp行为进行了实验研究。所得结果如下。（1）在表面活性剂溶液的流动中，发夹状涡旋的产生频率比在水流中低。(2)In表面活性剂溶液的流动，涡腿的扭结区和二次涡都很难发展。(3)At在低层位置，在水流中观察到多个低速条纹。另一方面，在表面活性剂溶液的流动中只能观察到单一的低速条纹。（4）表面活性剂溶液中涡头对流速度与局部流速之比小于水中。（5）表面活性剂溶液流动中发夹涡的颈部与壁面的夹角较小[单发夹涡]（1）表面活性剂溶液流动中要产生单发夹涡，必须有较高的射流速度和较短的射流持续时间。（2）当剪切速率大于剪切诱导态的临界值时，表面活性剂溶液流动中的发夹涡不会发展。（3）在极限条件下，可以产生单发夹涡。

In order to clarify the mechanism of drag-reduction in the turbulent flow of a surfactant solution, the behavior of hairp in vortex generated continuously or solitary in a laminar flat-plate boundary layr was investigated experimentally. The results obtainedare as follows.[continuously generated hairpin vortex](1)The frequency of hairpin generation is lower in the flow of surfactant solution than in the water flow.(2)In the flow of surfactant solution, both the kinked region of the vortex legs and the secondary votex are hard to develop.(3)At downsream location, multiple low-speed streaks are observed in the water flow. On the other hand, only single low -speed streak can be observed in the flow of surfactant solution.(4)The ratio of the convecting velocity of the vortex head to the local flow velocity is smaller in the surfactant solution thon in the water.(5)The angle between the neck of hairpin vortex and the wall is smaller in the flow of surfactant solution[single hairpin vortex](1)In order to generate a single hairpin vortex in the flow of surfactant solution, the speed of the infecting jet must be higher and the duration time must be shorter.(2)The hairpin vortex in the flow of surfactant solution does not develop if the shear rate is higher than the critical value for the shear inducing state.(3)The single hairpin vortex can be generated for the limiting conditions.