Flow around six in-line square cylinders
Flow around six in-line square cylinders
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DOI：
10.1017/jfm.2012.359
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发表时间：
2012-09
影响因子：
3.7
通讯作者：
C. Sewatkar;Rahul Patel;A. Sharma;A. Agrawal
中科院分区：
文献类型：
--
作者：
C. Sewatkar;Rahul Patel;A. Sharma;A. Agrawal
摘要 已经以 0 美元的成本对六个直列方形圆柱体周围的流动进行了数值和实验研究。 5\leq s/ d\leq 10. 0$ 和 $80\leq \mathit{Re}\leq 320$ ，其中 $s$ 是两个圆柱体之间的表面到表面距离，$d$ 是圆柱体的尺寸，$\mathit{Re}$ 是雷诺数。间距对流态的影响最初在 $\mathit{Re}= 100$ 时进行数值研究，其中在 $0 时观察到同步流态。 5\leq s/ d\leq 1. 1$ ，而准周期-I、准周期-II 和混沌状态出现在 $1. 5\leq s/ d\leq 1. 1$ 之间。 2\leq s/ d\leq 1. 3$ , $1. 4\leq s/ d\leq 5. 0$ 和 $6.分别为 0\leq s/ d\leq 10. 0$ 。这些机制已通过基于粒子图像测速的实验得到证实。提出了流动状态图作为间距和雷诺数的函数。在较高雷诺数下，流动主要是准周期 II 或混沌。流动的准周期和混沌性质是由于上游气缸的尾流干扰效应造成的，这种效应在雷诺数较高时变得更加严重。流态的外观与一排圆柱体的流态相反。所有气缸的涡流脱落的斯特劳哈尔数都是相同的，特别是对于同步和准周期 I 流态。无论间距如何，圆柱体所经历的平均阻力 ( ${C}_{Dmean} $ ) 都小于孤立圆柱体的平均阻力 ( ${C}_{Dmean} $ )。第一个气缸对下游气缸的存在相对不敏感，并且 ${C}_{Dmean} $ 几乎恒定为 1.2。第二个和第三个圆柱体的${C}_{Dmean}$可能为负值，${C}_{Dmean}$的值随着间距单调增加。均方根升力系数的变化与${C}_{Dmean} $ 的变化一致。有趣的是，瞬时升力可以大于气缸上的瞬时阻力。这些结果应该有助于提高对多个钝体周围流动的理解。
Abstract The flow around six in-line square cylinders has been studied numerically and experimentally for $0. 5\leq s/ d\leq 10. 0$ and $80\leq \mathit{Re}\leq 320$ , where $s$ is the surface-to-surface distance between two cylinders, $d$ is the size of the cylinder and $\mathit{Re}$ is the Reynolds number. The effect of spacing on the flow regimes is initially studied numerically at $\mathit{Re}= 100$ for which a synchronous flow regime is observed for $0. 5\leq s/ d\leq 1. 1$ , while quasi-periodic-I, quasi-periodic-II and chaotic regimes occur between $1. 2\leq s/ d\leq 1. 3$ , $1. 4\leq s/ d\leq 5. 0$ and $6. 0\leq s/ d\leq 10. 0$ , respectively. These regimes have been confirmed via particle-image-velocimetry-based experiments. A flow regime map is proposed as a function of spacing and Reynolds number. The flow is predominantly quasi-periodic-II or chaotic at higher Reynolds numbers. The quasi-periodic and chaotic nature of the flow is due to the wake interference effect of the upstream cylinders which becomes more severe at higher Reynolds numbers. The appearance of flow regimes is opposite to that for a row of cylinders. The Strouhal number for vortex shedding is the same for all the cylinders, especially for synchronous and quasi-periodic-I flow regimes. The mean drag ( ${C}_{Dmean} $ ) experienced by the cylinders is less than that for an isolated cylinder, irrespective of the spacing. The first cylinder is relatively insensitive to the presence of downstream cylinders and the ${C}_{Dmean} $ is almost constant at 1.2. The ${C}_{Dmean} $ for the second and third cylinders may be negative, with the value of ${C}_{Dmean} $ increasing monotonically with spacing. The changes in root mean square lift coefficient are consistent with changes in ${C}_{Dmean} $ . Interestingly, the instantaneous lift force can be larger than the instantaneous drag force on the cylinders. These results should help improve understanding of flow around multiple bluff bodies.