Abstract In this work, the three-dimensional structure of the boundary layer in the context of the vortex induced vibration of a circular cylinder is presented and investigated for the first time. Large-eddy simulations of a low mass ratio ( m = 2.6 ) two-degrees of freedom circular cylinder at the subcritical Reynolds number R e = 5300 and zero damping ( ζ = 0 ) for several reduced velocities of the system have been performed. A detailed description of the flow topology at the cylinder boundary layer and in the near wake for the three branches of structural response, i.e. the initial (I), super-upper (SU) and lower (L) branches, is presented. In the SU branch, the boundary layer becomes three-dimensional due to the emergence of streamwise vortices which are associated to the onset of a centrifugal instability that occurs twice every cycle. This is the first time a centrifugal instability in a freely vibrating system is reported. The streamwise structures with alternating vorticity, called here Taylor-Gortler vortices, are described and characterised. It is shown that their wavelength is in agreement with that of other centrifugal instabilities observed in forced sinusoidal oscillating cylinders.

中文翻译：

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涡激振动现象中Taylor-Görtler结构的形成

摘要 在这项工作中，首次提出并研究了圆柱涡激振动背景下边界层的三维结构。在亚临界雷诺数 Re = 5300 和零阻尼 ( ζ = 0 ) 下，低质量比 ( m = 2.6 ) 两个自由度圆柱体的大涡模拟已针对系统的几种降低速度进行。详细描述了结构响应的三个分支，即初始 (I)、超上 (SU) 和下 (L) 分支的圆柱边界层和近尾流中的流动拓扑。在 SU 分支中，由于流动涡流的出现，边界层变为三维，这与每个循环发生两次的离心不稳定性的开始有关。这是首次报道自由振动系统中的离心不稳定性。描述和表征了具有交替涡度的流向结构，这里称为 Taylor-Gortler 涡流。结果表明，它们的波长与在强制正弦振荡圆柱体中观察到的其他离心不稳定性的波长一致。