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采用一种新的流场显示方法(激光片光运动法)和不同实验方案对湍流边界层中的马蹄涡(或称发卡涡)进行了实验研究,其中包括马蹄涡的生成和发展过程。实验结果表明,湍流边界层中马蹄涡的一种主要生成方式是二次不稳定。其生成和发展过程既不同于层流中人工生成的马蹄涡;也不同于目前存在于人们观念中的那种完美的马蹄涡。这种马蹄涡有以下特征:(1)涡头部分展向尺度不断线性增长,最后固定在某个尺度;(2)涡头部沿流向作匀速运动;(3)流向涡管存在拉伸和变形。
A new flow field display method (laser light motion method) and different experimental schemes were used to investigate the horseshoe vortex (or hairpin vortex) in the turbulent boundary layer, including the generation and development of horseshoe vortex. The experimental results show that the main generation mode of horseshoe vortex in turbulent boundary layer is quadratic instability. Its formation and development process is different from the artificially generated horseshoe vortex in laminar flow, and also differs from the perfect horseshoe vortex that currently exists in people’s minds. The horseshoe vortex has the following characteristics: (1) the vortex head part grows linearly and continuously at a certain scale; (2) the vortex head part moves uniformly along the flow direction; (3) Deformation.