Velocity gradient tensor invariants are used to extract flow physics near the turbulent and nonturbulent interfaces (TNTIs) of cylinder and airfoil wakes with vortex shedding in conjunction with spatially developing direct numerical simulation. Conditional sampling is performed on fuzzy-cluster-method-resolved TNTIs using a novel subzone approach in which each instantaneous TNTI is subdivided into four categories: trough, bulge, leading edge, and trailing edge. Results of the conditionally sampled statistics, topology, and orientation of TNTI local structures suggest that wake TNTI properties depend more heavily on the degree of vortex shedding and relatively less on the degree of wake symmetry. The present subzone-sampled joint probability density functions of the second and the third invariants of the velocity gradient tensor are compared with existing jet and mixing layer observations, and new insights are extracted. Random relative orientation between the vorticity vector and the TNTI normal is observed in the trough subzone of the present wake TNTIs, which casts doubts on the notion of full vortex structure confinement. The turbulent flow near the trailing edge subzone of wake TNTI is found to be the most effective in enstrophy production, whereas the turbulent flow in the leading-edge portion is the least effective.

速度梯度张量不变量用于提取带有涡旋脱落的圆柱和翼型尾流的湍流和非湍流界面 (TNTI) 附近的流动物理，并结合空间发展的直接数值模拟。使用新的子区域方法对模糊聚类方法解析的 TNTI 执行条件采样，其中每个瞬时 TNTI 细分为四类：谷、凸、前缘和后缘。TNTI 局部结构的条件采样统计、拓扑和方向的结果表明，尾流 TNTI 属性更依赖于涡旋脱落的程度，而相对较少地依赖于尾流对称度。将当前的子带采样联合概率密度函数的速度梯度张量的第二和第三不变量与现有的射流和混合层观测进行比较，并提取出新的见解。在当前尾流 TNTI 的槽子带中观察到涡量矢量与 TNTI 法线之间的随机相对取向，这对全涡结构限制的概念提出了质疑。发现尾流 TNTI 后缘子带附近的湍流在形成对映中最有效，而前缘部分的湍流最不有效。这对全涡流结构约束的概念提出了质疑。发现尾流 TNTI 后缘子带附近的湍流在形成对映中最有效，而前缘部分的湍流最不有效。这对全涡流结构约束的概念提出了质疑。发现尾流 TNTI 后缘子带附近的湍流在形成对映中最有效，而前缘部分的湍流最不有效。