Collapse and pinch-off of a non-axisymmetric impact-created air cavity in water
Collapse and pinch-off of a non-axisymmetric impact-created air cavity in water
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DOI：
10.1017/jfm.2012.130
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发表时间：
2011-09
影响因子：
3.7
通讯作者：
Oscar R. Enríquez;I. Peters;S. Gekle;Laura E. Schmidt;D. Lohse;D. Meer
中科院分区：
文献类型：
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作者：
Oscar R. Enríquez;I. Peters;S. Gekle;Laura E. Schmidt;D. Lohse;D. Meer
摘要水中圆柱形空腔的轴对称坍缩遵循一个具有对数修正的普遍幂律。尽管如此，有人认为，引入一个小的方位角扰动会引起长期记忆效应，反映在不再普遍但记住初始条件的振荡中。在这项工作中，我们通过驱动金属盘通过最初静止的水面来创建非轴对称的空气腔，并观察它们随后的重力诱导塌陷。这些空腔具有单模数$m$和振幅${a}_{m} $的方位角谐波扰动特征。对于较小的初始畸变幅度（平均盘半径的1%或2%），空腔壁在坍塌过程中呈线性振荡，振幅几乎恒定，频率增加。随着振幅的增加，在振荡中触发更高的谐波，我们观察到更复杂的掐断模式。对于小振幅扰动，我们将实验结果与Schmidt等人的振荡振幅模型进行比较。《流体力学》，2009年第5卷，第343-346页)和Bergmann等人先前提出的轴对称冲击空腔坍塌模型（J. Fluid Mech.）。， vol. 633, 2009b, pp. 381-409)。通过结合这两个模型，我们可以在掐断之前的任何时间重建空腔的三维形状。
Abstract The axisymmetric collapse of a cylindrical air cavity in water follows a universal power law with logarithmic corrections. Nonetheless, it has been suggested that the introduction of a small azimuthal disturbance induces a long-term memory effect, reflecting in oscillations which are no longer universal but remember the initial condition. In this work, we create non-axisymmetric air cavities by driving a metal disc through an initially quiescent water surface and observe their subsequent gravity-induced collapse. The cavities are characterized by azimuthal harmonic disturbances with a single mode number $m$ and amplitude ${a}_{m} $. For small initial distortion amplitude (1 or 2 % of the mean disc radius), the cavity walls oscillate linearly during collapse, with nearly constant amplitude and increasing frequency. As the amplitude is increased, higher harmonics are triggered in the oscillations and we observe more complex pinch-off modes. For small-amplitude disturbances we compare our experimental results with the model for the amplitude of the oscillations by Schmidt et al. (Nature Phys., vol. 5, 2009, pp. 343–346) and the model for the collapse of an axisymmetric impact-created cavity previously proposed by Bergmann et al. (J. Fluid Mech., vol. 633, 2009b, pp. 381–409). By combining these two models we can reconstruct the three-dimensional shape of the cavity at any time before pinch-off.