Habibi Mehdi, Maleki Maniya, Golestanian Ramin, Ribe Neil M, Bonn Daniel
Institute for Advanced Studies in Basic Sciences, Zanjan 45195-1159, Iran.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Dec;74(6 Pt 2):066306. doi: 10.1103/PhysRevE.74.066306. Epub 2006 Dec 11.
We present a combined experimental and numerical investigation of the coiling of a liquid "rope" falling on a solid surface, focusing on three little-explored aspects of the phenomenon: The time dependence of "inertio-gravitational" coiling, the systematic dependence of the radii of the coil and the rope on the experimental parameters, and the "secondary buckling" of the columnar structure generated by high-frequency coiling. Inertio-gravitational coiling is characterized by oscillations between states with different frequencies, and we present experimental observations of four distinct branches of such states in the frequency-fall height space. The transitions between coexisting states have no characteristic period, may take place with or without a change in the sense of rotation, and usually (but not always) occur via an intermediate "figure of eight" state. We present extensive laboratory measurements of the radii of the coil and of the rope within it, and show that they agree well with the predictions of a "slender-rope" numerical model. Finally, we use dimensional analysis to reveal a systematic variation of the critical column height for secondary buckling as a function of (dimensionless) flow rate and surface tension parameters.
我们对落在固体表面的液体“绳索”的盘绕现象进行了实验与数值相结合的研究，重点关注该现象三个鲜有探索的方面：“惯性 - 重力”盘绕的时间依赖性、线圈半径和绳索半径对实验参数的系统依赖性，以及高频盘绕产生的柱状结构的“二次屈曲”。惯性 - 重力盘绕的特征是在不同频率状态之间振荡，我们展示了在频率 - 下落高度空间中此类状态的四个不同分支的实验观测结果。共存状态之间的转变没有特征周期，可以在旋转方向改变或不改变的情况下发生，并且通常（但并非总是）通过中间的“8 字形”状态发生。我们对线圈及其内部绳索的半径进行了广泛的实验室测量，并表明它们与“细长绳索”数值模型的预测结果吻合良好。最后，我们使用量纲分析揭示了二次屈曲临界柱高随（无量纲）流速和表面张力参数的系统变化。
