The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image methods. In this paper, the moving single-frame and long-exposure (MSFLE) image method is used to intuitively track the evolution process of a hairpin vortex, while the moving particle image velocimetry (moving-PIV) method is applied for obtaining a moving velocity field for quantitative analysis. According to the structural characteristics of the hairpin vortex, an inclined light sheet with an appropriate inclination of 53° is arranged to capture the complete hairpin vortex structure at Re_θ = 97–194. In addition, the core size and the rotational strength of a hairpin vortex are further defined and quantified by the Liutex vector method. The evolution process of a complete hairpin vortex structure observed by MSFLE shows that the shear along the normal direction leads to an increasing strength of the hairpin vortex, accompanied by a lifting vortex head and a distance decrease between two vortex legs during the dissipation period. By combining moving-PIV with the Liutex identification, the spatiotemporal evolution of four typical regions of a hairpin vortex projecting into a 53° cross-section is obtained. The results show that the process from the generation to the dissipation of a single hairpin vortex can be well characterized and recorded by the Liutex based on the core size and rotational intensity, and the evolution process is consistent with the MSFLE result. According to the statistics of vortex core size and rotation intensity along time, the evolution of the hairpin vortex necks and legs can be described as a process of enhancement followed by dissipation. For the vortex head, its evolution maintains longer attributed to its far-from-wall position, which consists of an absolute enhancement process (stage 1) with an increasing rotation strength and a constant core size, and an absolute dissipation (stage 2) with a decreasing rotation strength and a constant core size.

使用两种图像方法定性和定量研究了完全发展的湍流边界层中发夹涡结构的时空演化。本文采用移动单帧长曝光（MSFLE）图像方法直观地跟踪发夹涡旋的演化过程，而应用移动粒子图像测速（moving-PIV）方法获取移动速度定量分析领域。根据发夹涡流，倾斜光片与53的适当倾斜的结构特点°被布置为捕获在完整发夹旋涡结构重新_θ= 97–194。此外，发夹涡旋的核心尺寸和旋转强度通过 Liutex 矢量方法进一步定义和量化。MSFLE观测到的完整发夹涡结构的演化过程表明，沿法线方向的剪切导致发夹涡强度增加，并伴随着消散期间涡头抬升和两个涡腿之间的距离减小。通过将移动 PIV 与 Liutex 识别相结合，获得了投射到 53° 截面的发夹涡旋的四个典型区域的时空演化。结果表明，基于核心尺寸和旋转强度，Liutex可以很好地表征和记录单个发夹涡从产生到消散的过程，演化过程与 MSFLE 结果一致。根据涡核大小和旋转强度随时间的统计，发夹涡颈和涡腿的演化可描述为先增强后消散的过程。对于涡头，由于其远离壁面的位置，其演化保持更长的时间，其中包括具有增加的旋转强度和恒定核心尺寸的绝对增强过程（阶段 1），以及具有恒定核心尺寸的绝对耗散（阶段 2）降低的旋转强度和恒定的核心尺寸。