湍流边界层内暗斑拟序结构的可视化实验研究

Visualization Experimental Investigation on Dark Spot Coherent Structure in Turbulent Boundary Layer

采用氢气泡流动显示技术,以水为工质,对竖直矩形通道湍流边界层内的暗斑拟序结构进行了可视化实验研究,流动雷诺数Re=3 009。根据暗斑形成过程中其上游边界处是否产生涡旋,将暗斑划分为两种类型:三涡旋暗斑和双涡旋暗斑。对暗斑的形成过程及其速度分布进行了初步研究。通过与平板边界层内暗斑拟序结构对比发现:矩形通道内暗斑的发展时间较短,且其内部流体的速度增量较小。

The dark spot coherent structures in the turbulent boundary layer near the wall of a vertical rectangular channel were observed by using hydrogen bubble flow visu-alization techniques ,and the flow Reynolds number Re=3 009 .Based on the existence of the vortex in the upstream border , the dark spots were divided into two types ：Three-vortex dark spots and two-vortex dark spots .The dark spot formation process and its velocity distribution were preliminarily studied .Compared with dark spots in plate boundary layer ,the development time of dark spots in rectangular channel bounda-ry is shorter ,and its internal fluid velocity increment is weaker .