湍流边界层中下扫流与“反发卡涡”

用氢气泡法观测湍流边界层的下扫流和有关的流动结构.实验中发现一种新型涡结构，它的特征与典型的发卡涡正好相反.发卡涡的头部指向下游，而它的头部指向上游； 发卡涡的两腿之间，由于涡的诱导产生上升流，而它则在其两腿之间，由于涡的诱导产生下扫流. 关键词： 湍流边界层 流动显示 流动结构 发卡涡

The sweep down flow and "contra-hairpin vortex" in a turbulent boundary layer

The sweep down flow and related flow structures in a turbulent boundary layer were visualized with hydrogen bubble method. The streamwise and transverse vortices induced by sweep down flow near the wall of a vessel were observed. A new kind of vortical structure, whose features are contrary to those of the hairpin vortex, was observed in the present experiments. It is termed “contra hairpin vortex” here. Its head points upstream, while the head of a hairpin vortex points downstream; lift-up flow is induced between the legs of a hairpin vortex, while between the legs of this new vortical structure, sweep down flow is induced.