This study focuses on the characteristics of flow past three side-by-side rectangular cylinders under the effect of aspect ratios (AR) and Reynolds numbers (Re) at two different gap ratios (g) using the lattice Boltzmann method. For this purpose, AR is varied in the range of 0.25–4, the Re values are 100, 140 and 180 and the two different values of g taken into account are g=0.5 and 3. The results are presented in the form of vorticity contours, temporal histories of drag and lift coefficients and power spectrum of lift coefficients. Also, the variation of physical parameters like mean drag coefficient, Strouhal number and the root-mean-square values of drag and lift coefficients with Re and AR is presented for g=0.5 and 3. The current numerical computations yield that for both gap ratios and all Re, there exist four different flow regimes depending on AR: (a) steady flow, (b) modulated flow, (c) symmetric flow and (d) periodic flow. At narrow gap ratios, the jet flow emerging within the gaps of cylinders altered the flow structures and fluid forces abruptly. The aspect ratio is found to have more influence on the flow characteristics of cylinders as compared to the Reynolds numbers at large gap ratios.

中文翻译：

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长宽比和雷诺数影响下三个并列矩形圆柱体的流动特征

本研究重点研究在两种不同间隙比（G) 使用格子玻尔兹曼方法。为此，AR 在 0.25-4 范围内变化，Re 值为 100、140 和 180，两个不同的值为G考虑到是G=0.53. 结果以涡度等值线、阻力和升力系数的时间历程和升力系数的功率谱的形式呈现。此外，还给出了物理参数如平均阻力系数、斯特劳哈尔数以及阻力和升力系数的均方根值随 Re 和 AR 的变化G=0.53. 目前的数值计算得出，对于间隙比和所有 Re，存在四种不同的流态，具体取决于 AR：(a) 稳定流，(b) 调制流，(c) 对称流和 (d) 周期流. 在窄间隙比下，圆柱间隙内出现的射流突然改变了流动结构和流体力。与大间隙比下的雷诺数相比，发现纵横比对气缸的流动特性有更大的影响。