Even though the analysis of unsteady 2D flow fields is challenging, fluid mechanics experts generally have an intuition on where in the simulation domain specific features are expected. Using this intuition, showing similar regions enables the user to discover flow patterns within the simulation data. When focusing on similarity, a solid mathematical framework for a specific flow pattern is not required. We propose a technique that visualizes similar and dissimilar regions with respect to a region selected by the user. Using infinitesimal strain theory, we capture the strain and rotation progression and therefore the dynamics of fluid parcels along pathlines, which we encode as distributions. We then apply the Jensen-Shannon divergence to compute the (dis)similarity between pathline dynamics originating in a user-defined flow region and the pathline dynamics of the flow field. We validate our method by applying it to two simulation datasets of two-dimensional unsteady flows. Our results show that our approach is suitable for analyzing the similarity of time-dependent flow fields.

翻译：尽管非稳态二维流场的分析具有挑战性，但流体力学专家通常对模拟域中特定特征的预期位置具有直观判断。利用这一直觉，展示相似区域能够帮助用户发现模拟数据中的流动模式。在关注相似性时，无需针对特定流动模式建立严格的数学框架。我们提出一种技术，用于可视化用户选择区域与其他区域的相似性与差异性。基于无穷小应变理论，我们捕捉沿迹线的应变与旋转发展过程（即流体微团的动力学特征），并将其编码为分布。随后，利用詹森-香农散度计算用户定义流动区域中迹线动力学与整个流场迹线动力学之间的（相）似性。通过将方法应用于两个二维非稳态流模拟数据集进行验证，结果表明我们的方法适用于分析时变流场的相似性。