壁面湍流发卡涡包空间模态的TRPIV实验研究

运用高时间分辨率粒子图像测速(Time-resolved PIV简称TRPIV),测量得到平板湍流边界层流向/法向平面内瞬时速度矢量空间分布的时间序列;采用空间局部平均速度结构函数的概念,识别和提取湍流边界层中大尺度发卡涡包结构的空间特征。发现在湍流边界层中不同法向位置多个正负发卡涡包结构同时交替存在。这些分布在不同法向高度的发卡涡包结构之间通过倾斜的涡量剪切层相联系,构成了湍流边界层中内、外区紧密相连、相互作用的一种稳态的分布方式。

TRPIV Experimental Study of Hairpin Vortex Packet Spatial Mode in Turbulent Boundary Layer

Time series of instantaneous velocity vector spatial distribution in both streamline plane/ normal plane of flat plate turbulent boundary layer were measured, respectively, by using high time resolution particle image velocimetry (TRPIV). Space characteristics of large-scale hairpin vortex packets in turbulent boundary layer were identified and extracted based on the concept of space locally averaged velocity structure function. It is found that along different normal positions in turbulent boundary layer from near-wall area to outer layer, multiple positive and negative hairpin vortex packets alternately coexist. These hairpin vortex packet structures distributed in different heights along normal direction are connected each other through tilted vortex shear layer, which enables the middle and inner layer to closely connect with the outer region in turbulent boundary layer and to constitute an interactional steady-state.