The aim of the article is to propose a simple engineering method for identifying and characterizing vortical structures within a flow field measured with a classic two-component PIV measurement system. Some of the most popular vortex detection systems are briefly presented. Of these, many fail if spurious vectors are present within the flow field due to poor PIV image quality or due to particle voids in the vortex core. The chosen method is the Γ2-criterion. The investigated method is robust and reliable, because it is based on the velocity field topology without using velocity derivatives sensitive to the spurious vectors. The method is tested on synthetic velocity fields of ideal vortices and on real PIV velocity field of a four-bladed rotor wake. The synthetic velocity fields reproduce single and multiple vortices to investigate the mutual interaction and the effect on the vortex detection criteria. The synthetic velocity fields have different spatial resolution, noise level, and different particle void to perform a parametric assessment. Other vortex identification schemes are applied for comparison. Information on how to use the criterion for different noise conditions, particle void, and presence of multiple vortices is provided.

中文翻译：

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旋翼机应用中 PIV 数据的涡流检测标准评估

本文的目的是提出一种简单的工程方法，用于识别和表征使用经典双分量 PIV 测量系统测量的流场内的涡旋结构。简要介绍了一些最流行的涡流检测系统。其中，如果由于 PIV 图像质量差或涡核中的颗粒空隙而导致流场中存在虚假矢量，则许多会失败。选择的方法是Γ2 准则。所研究的方法稳健可靠，因为它基于速度场拓扑结构，而不使用对虚假矢量敏感的速度导数。该方法在理想涡流的合成速度场和四叶转子尾流的真实 PIV 速度场上进行了测试。合成速度场再现单个和多个涡流，以研究相互之间的相互作用以及对涡流检测标准的影响。合成速度场具有不同的空间分辨率、噪声水平和不同的粒子空隙以执行参数评估。应用其他涡流识别方案进行比较。提供了有关如何针对不同噪声条件、粒子空隙和存在多个涡流使用该准则的信息。