The present study focuses on the flow over a 2D square cylinder with a plate placed in front of it. An in-house code using the lattice Boltzmann method was employed for all the simulations presented. Few cases were simulated using the open source code Nektar ++, the results obtained from both methodologies were compared. Regarding the plate, three related parameters, velocity ratio, distance between the plate and cylinder and the thickness of the plate, were studied in order to evaluate the impact of these parameters on the flow behavior. The interactions between these parameters were as well investigated. The effect of these parameters on flow transitional properties such as Hopf and Neimark–Sacker bifurcations were discussed. Whenever the velocity ratio exceeds a certain value, Kelvin–Helmholtz instabilities dominate the vortex shedding. As velocity ratio increases, drag coefficient and vortex shedding frequency increase. The POD method was employed to predict the flow behavior based on the existing information. It turned out the POD method is a trustable methodology to mathematically pre-investigate the flow field, therefore it is capable of saving large computational resources.

中文翻译：

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低雷诺数下带有上游分流板的方形圆柱体周围流动的数值研究

本研究的重点是在 2D 方形圆柱体上的流动，该圆柱体前面有一块板。使用格子 Boltzmann 方法的内部代码用于呈现的所有模拟。使用开源代码 Nektar ++ 模拟了几个案例，比较了两种方法获得的结果。关于板，研究了三个相关参数，速度比、板与筒之间的距离和板的厚度，以评估这些参数对流动行为的影响。还研究了这些参数之间的相互作用。讨论了这些参数对流动过渡特性的影响，例如 Hopf 和 Neimark-Sacker 分岔。每当速度比超过某个值时，开尔文-亥姆霍兹不稳定性就会主导涡旋脱落。随着速度比增加，阻力系数和涡旋脱落频率增加。POD 方法被用来预测基于现有信息的流动行为。事实证明，POD方法是一种可靠的数学预研究流场方法，因此能够节省大量计算资源。