We put forward the idea of defining vortex boundaries in planar flows as closed material barriers to the diffusive transport of vorticity. Such diffusive vortex boundaries minimize the leakage of vorticity from the fluid mass they enclose when compared to other nearby material curves. Building on recent results on passive diffusion barriers, we develop an algorithm for the automated identification of such structures from general, two-dimensional unsteady flow data. As examples, we identify vortex boundaries as vorticity diffusion barriers in two flows: an explicitly known laminar flow and a numerically generated turbulent Navier-Stokes flow.

中文翻译：

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涡旋边界是二维流动中扩散涡旋传输的障碍

我们提出了将平面流中的涡旋边界定义为封闭的物质壁垒的想法，这些壁垒阻碍了涡流的扩散传输。当与其他附近的材料曲线相比时，这种扩散涡旋边界使涡旋从它们所包围的流体质量中的泄漏最小化。基于被动扩散壁垒的最新研究结果，我们开发了一种算法，可根据一般的二维非定常流动数据自动识别此类结构。作为示例，我们将涡流边界确定为两种流中的涡流扩散障碍：显式已知的层流和数值生成的湍流Navier-Stokes流。