To more clearly understand the changes in flow characteristics around two square cylinders with different spacing ratios, the main mode of the flow field was extracted by using the Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) methods. The changes in the main mode of the flow field at different spacing ratios and the difference of the time series were analyzed and compared. This processing can separate the mixed information in the flow field and obtain the dominant modes in the flow field. These main modes can clearly reflect the dominant flow characteristics in the flow field. The analysis results show that when L/D = 2, the flow field structure is consistent with the flow field around a single square cylinder. When L/D = 2.5–3.5, the vortex shedding from upstream cylinders combines with the vortex near the downstream cylinders. This mutual coupling causes a significant change in the drag coefficient value of the downstream cylinder. When L/D = 4, the main vortex from the upstream cylinder can be completely shed, which means that the upstream and downstream square cylinder vortices start to become independent. The main focus of this paper is to use the advantages of POD and DMD to obtain several modes with higher energy in the flow field. Furthermore, it can be considered that these main modes can fully reflect the flow characteristics of the flow field.

中文翻译：

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基于POD和DMD方法的不同间距比串联布置的两个方圆柱绕流的数值分析。

为了更清楚地了解具有不同间距比的两个方形圆柱体周围的流动特性变化，使用适当的正交分解（POD）和动态模式分解（DMD）方法提取了流场的主模。分析并比较了不同间距比下流场主模的变化以及时间序列的差异。该处理可以分离流场中的混合信息并获得流场中的主导模式。这些主要模式可以清楚地反映流场中的主要流动特性。分析结果表明，当L / D = 2时，流场结构与单个方形圆柱体周围的流场一致。当L / D = 2.5-3.5时，从上游圆柱体脱落的涡流与下游圆柱体附近的涡流相结合。这种相互耦合导致下游气缸的阻力系数值发生重大变化。当L / D = 4时，上游圆柱体的主涡流可以完全消除，这意味着上游和下游方圆柱体涡流开始变得独立。本文的主要重点是利用POD和DMD的优势来获得流场中能量较高的几种模式。此外，可以认为这些主要模式可以充分反映流场的流动特性。这意味着上游和下游方圆柱涡开始变得独立。本文的主要重点是利用POD和DMD的优势来获得流场中能量较高的几种模式。此外，可以认为这些主要模式可以充分反映流场的流动特性。这意味着上游和下游方圆柱涡开始变得独立。本文的主要重点是利用POD和DMD的优势来获得流场中能量较高的几种模式。此外，可以认为这些主要模式可以充分反映流场的流动特性。