Two-dimensional numerical study of vortex shedding regimes of oscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers
Two-dimensional numerical study of vortex shedding regimes of oscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers
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DOI：
10.1017/jfm.2014.268
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发表时间：
2014-06
影响因子：
3.7
通讯作者：
Ming Zhao;Liang Cheng
中科院分区：
文献类型：
--
作者：
Ming Zhao;Liang Cheng
摘要采用有限元法求解二维Navier-Stokes方程，数值模拟了低雷诺数下并列和串列双圆柱的振荡绕流。本研究的目的是确定在不同的间隙安排和Keulegan-Carpenter数（KC）的两个圆柱系统的流动状态。在七个间隙比$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}\let \le =\leqslant \let \leq =\leqslant\let \ge =\geqslant\let\geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}G$下进行模拟。（$G=L/D$，其中$L$是圆柱体与圆柱体之间的间隙，$D$是圆柱体的直径）为0.5、1、1.5、2、3、4和5，KC的范围为1至12，间隔为0.25。在两个圆柱体系统中也观察到了围绕单个圆柱体的振荡流的流态，但是由于两个圆柱体之间的相互作用而具有不同的流态。在并排布置中，当差距比小时，来自两个气缸之间的差距的旋涡脱落占主导地位，从而导致差距旋涡脱落（GVS）状态，该状态不同于针对单个气缸确定的任何流状态。对于并排布置中的1.5和2的中间间隙比，来自每个圆柱的一侧的旋涡脱落模式不一定与来自另一侧的旋涡脱落模式相同，形成所谓的组合流态。当两个圆柱之间的差距比足够大时，每个圆柱的旋涡脱落与单个圆柱的旋涡脱落相似。在串联布置中，当两个气缸之间的差距非常小时，流态类似于单个气缸的流态。在大间隙比的串列布置中，来自两个圆柱的差距侧的旋涡脱落流相互作用，而来自圆柱外侧的旋涡脱落流受另一个圆柱的存在影响较小，与单个圆柱的旋涡脱落流相似。对于并排和串联布置，两个圆柱体的旋涡脱落流之间的强烈相互作用使得在大KC值下流动非常不规则。
Abstract Oscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers is simulated numerically by solving the two-dimensional Navier–Stokes (NS) equations using a finite-element method (FEM). The aim of this study is to identify the flow regimes of the two-cylinder system at different gap arrangements and Keulegan–Carpenter numbers (KC). Simulations are conducted at seven gap ratios $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}G$ ( $G=L/D$ where $L$ is the cylinder-to-cylinder gap and $D$ the diameter of a cylinder) of 0.5, 1, 1.5, 2, 3, 4 and 5 and KC ranging from 1 to 12 with an interval of 0.25. The flow regimes that have been identified for oscillatory flow around a single cylinder are also observed in the two-cylinder system but with different flow patterns due to the interactions between the two cylinders. In the side-by-side arrangement, the vortex shedding from the gap between the two cylinders dominates when the gap ratio is small, resulting in the gap vortex shedding (GVS) regime, which is different from any of the flow regimes identified for a single cylinder. For intermediate gap ratios of 1.5 and 2 in the side-by-side arrangement, the vortex shedding mode from one side of each cylinder is not necessarily the same as that from the other side, forming a so-called combined flow regime. When the gap ratio between the two cylinders is sufficiently large, the vortex shedding from each cylinder is similar to that of a single cylinder. In the tandem arrangement, when the gap between the two cylinders is very small, the flow regimes are similar to that of a single cylinder. For large gap ratios in the tandem arrangement, the vortex shedding flows from the gap side of the two cylinders interact and those from the outer sides of the cylinders are less affected by the existence of the other cylinder and similar to that of a single cylinder. Strong interaction between the vortex shedding flows from the two cylinders makes the flow very irregular at large KC values for both side-by-side and tandem arrangements.