Laboratory experiments with a rotating cylindrical annulus are reported that reveal a prograde jet, which is adjacent to a (longitudinally) librating inner straight cylindrical wall. Here, wall libration is realised as a time-harmonic modulation of the inner cylinder's rotation rate. The outer cylindrical wall and bottom and top lids rotate with constant angular velocity. The main purpose of our study is to contribute to a qualitative and quantitative understanding of non-linearities that are present in oscillating, but centrifugally stable, vertical boundary layers frequently encountered in rotating wall-bounded flows. We consider a problem that is in a sense complementary to that of previous works that focused on oscillating Ekman layers but neglected the vertical Stokes−Stewartson layers. A simple analytical model is proposed that is able to predict the magnitude and spatial structure of the emerging prograde near-wall jet in terms of nonlinearity inherent in the inner cylinder's boundary layer dynamics.

中文翻译：

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由于旋转环的侧壁纵向振动而产生的平均流

据报道，使用旋转圆柱形环的实验室实验揭示了一个顺行射流，它与（纵向）振动的内部直圆柱壁相邻。在这里，壁振动被实现为内圆柱体转速的时谐调制。外圆柱壁以及底盖和顶盖以恒定角速度旋转。我们研究的主要目的是有助于对非线性的定性和定量理解，这些非线性存在于旋转壁限流中经常遇到的振荡但离心稳定的垂直边界层。我们考虑的问题在某种意义上与之前的工作是互补的，这些工作专注于振荡 Ekman 层但忽略了垂直 Stokes-Stewartson 层。