We discuss the behavior of a flexible sheet placed in the wake of a cylinder that is forced to rotate periodically. This is done through a series of experiments conducted in a water tunnel and by simultaneously visualizing the flow behavior and tracking the motion of the flexible sheet in the wake of the cylinder. We show how the response of a flexible sheet in the wake of a fixed cylinder, which is the result of the sheet’s interaction with the vortices that are shed at a frequency predicted by the Strouhal law can be changed to a “desired” response by forcing the upstream cylinder to rotate periodically. Large-amplitude oscillations at a frequency different from the Strouhal frequency can be imposed on the flexible sheet, and the sheet’s oscillations can be suppressed if the cylinder is forced to rotate at a higher frequency. The flexible sheet finds its way in between the vortices that are shed in the wake of the cylinder, and by controlling the frequency and location of the shed vortices in the wake of the cylinder, one can impose a desired motion on the sheet. Besides imposing a symmetric oscillatory response on the sheet, we show that asymmetric responses can be imposed on the sheet when an asymmetric waveform is used to force the upstream cylinder.

中文翻译：

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柔性片材跟随圆柱体被迫旋转

我们讨论放置在被迫周期性旋转的圆柱体尾部的柔性片材的行为。这是通过在水洞中进行的一系列实验来完成的，同时可视化流动行为并跟踪柔性片材在圆柱体尾流中的运动。我们展示了柔性片材在固定圆柱体之后的响应如何通过强制改变为“期望的”响应，这是片材与以斯特劳哈尔定律预测的频率脱落的涡流相互作用的结果上游气缸周期性旋转。可以在柔性片材上施加与斯特劳哈尔频率不同的频率的大振幅振荡，并且如果迫使圆柱体以更高的频率旋转，则可以抑制片材的振荡。柔性片材在圆柱体尾流中脱落的涡流之间找到路径，并且通过控制在圆柱体尾流中脱落的涡流的频率和位置，人们可以在片材上施加期望的运动。除了在薄片上施加对称振荡响应之外，我们还表明，当使用不对称波形来推动上游圆柱体时，可以在薄片上施加不对称响应。