THREE-DIMENSIONAL FLOQUET INSTABILITY OF THE WAKE OF SQUARE CYLINDER
THREE-DIMENSIONAL FLOQUET INSTABILITY OF THE WAKE OF SQUARE CYLINDER
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DOI：
10.1063/1.869930
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发表时间：
1999-02
影响因子：
4.6
通讯作者：
J. Robichaux;S. Balachandar;S. Vanka
中科院分区：
文献类型：
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作者：
J. Robichaux;S. Balachandar;S. Vanka
在这项研究中，我们研究了方形圆柱体的二维周期性尾流中三维性的开始。采用Floquet稳定性分析来提取三维不稳定性的不同模式。据观察，方柱体的三维转变过程与圆柱体的三维转变过程类似。最值得注意的是，存在长波长（模式 A）三维扰动，首先在雷诺数约为 161 时变得不稳定，然后是短波长（模式 B）三维扰动，在雷诺数约为 190 时变得不稳定。此外，还观察到第三中波长模式在 Re=200 左右变得不稳定。与模式 A 和 B 不同，中波长模式是次谐波，其周期是二维基态脱落周期的两倍。该模式还打破了在其他两种模式中观察到的反射平移对称性，因此出现了重数二。详细探讨了三种模式的时空对称性。
In this study we investigate the onset of three-dimensionality in an otherwise two-dimensional periodic wake of a square cylinder. Floquet stability analysis is employed to extract the different modes of three-dimensional instabilities. It is observed that the three-dimensional transition process for a square cylinder is similar to that of a circular cylinder. Most notably, there is a long-wavelength (mode A) three-dimensional disturbance that becomes unstable first at a Reynolds number of about 161, followed by a short-wavelength (mode B) three-dimensional disturbance that becomes unstable at a Reynolds number of about 190. In addition, a third intermediate-wavelength mode is also observed to become unstable at around Re=200. Unlike modes A and B, the intermediate-wavelength mode is subharmonic with a period of twice the shedding period of the two-dimensional base state. This mode also breaks the reflection translation symmetry observed in the other two modes and as a result appears with multiplicity two. The space–time symmetries of the three modes are explored in detail.