湍流边界层中马蹄涡的实验研究

采用~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~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。

EXPERIMENTAL STUDY FOR THE HORSESHOE VORTEX IN TURBULENT BOUNDARY LAYER

Experimental study was performed for the formation and development of the horseshoe vortex in turbulent boundary layer through using a new method of visualization (moving sheet of laser light) and several experimental skills. The test results show that a main process of formation of the horseshoe vortex in turbulent boundary layer is a secondary instability, which is not different from the horseshoe vortex caused by artificial method in laminar boundary layer and the horseshoe vortexregarded as consummate horseshoe shape usually. In addition, it has rules and characteristics as follows: (1) The transverse size of it increases at uniform velocity up to its stable size; (2) It keeps a uniform motion in longitudinal direction after it forms; (3) Longitudinal vortices have stretch and deformation.