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

表面活性剂溶液层流边界层中发夹旋涡的行为

基本信息

批准号：
06650203
负责人：
ITOH Motoyuki
金额：
$ 1.34万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650203/
关键词：
drag reduction surfactant solution hairpin vortex low-speed streak flat-plate boundary layr hydrogen bubble method dye injection technique

项目摘要

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.

为了阐明表面活性剂溶液湍流流动中的减阻机理，实验研究了层流平板边界层中连续和孤立产生的涡流中毛发的行为。得到的结果如下：(1)在表面活性剂溶液流动中，发夹的产生频率比在水流中低。(2)在表面活性剂溶液流动中，涡腿的结合区和二次涡都很难发展。(3)在下游位置，水流中观察到多条低速条纹。另一方面，在表面活性剂溶液中只能观察到单一的低速条纹。(4)在水中，涡头的对流速度与局部流动速度的比值较小。(5)在表面活性剂溶液的流动中，发卡式涡颈与壁面的夹角较小。(1)为了在表面活性剂溶液流动中产生单一的发卡式涡流，感染射流的速度必须更高，持续时间必须更短。(2)当剪切速率高于剪切诱导状态的临界值时，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，可以产生单一的发卡涡。