Free rings of bouncing droplets: stability and dynamics
Free rings of bouncing droplets: stability and dynamics
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DOI：
10.1017/jfm.2020.648
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发表时间：
2020-11-25
影响因子：
3.7
通讯作者：
Bush, John W. M.
中科院分区：
文献类型：
--
作者：
Couchman, Miles M. P.;Bush, John W. M.
我们给出了实验和理论相结合的结果，研究了毫米级液滴在振动液槽表面反弹的稳定性。随着熔池振动加速度的逐渐增加，液滴环被发现失稳为各种动力学状态，包括稳定的旋转运动、周期性的径向或方位向振荡和方位向行波。观测到的不稳定性取决于环的初始半径和液滴数量，以及液滴相对于相邻液滴是同相反弹还是异相反弹。随着振动加速度的进一步增加，出现了更多的奇异动力学，包括准周期运动和重排成规则的多边形结构。基于Couchman等人理论模型的环的线性稳定性分析和仿真。(《流体力学》，第871卷，2019年，第212-243页)基本上复制了观察到的行为。我们证明了每个液滴下方的波幅对多液滴结构的稳定性有显著的影响：系统寻求最小化碰撞时液滴下方的平均波幅。我们的工作提供了对弹跳液滴聚集体中出现的复杂相互作用和集体运动的洞察。
We present the results of a combined experimental and theoretical investigation of the stability of rings of millimetric droplets bouncing on the surface of a vibrating liquid bath. As the bath's vibrational acceleration is increased progressively, droplet rings are found to destabilize into a rich variety of dynamical states including steady rotational motion, periodic radial or azimuthal oscillations and azimuthal travelling waves. The instability observed is dependent on the ring's initial radius and drop number, and whether the drops are bouncing in- or out-of-phase relative to their neighbours. As the vibrational acceleration is further increased, more exotic dynamics emerges, including quasi-periodic motion and rearrangement into regular polygonal structures. Linear stability analysis and simulation of the rings based on the theoretical model of Couchman et al. (J. Fluid Mech., vol. 871, 2019, pp. 212-243) largely reproduce the observed behaviour. We demonstrate that the wave amplitude beneath each drop has a significant influence on the stability of the multi-droplet structures: the system seeks to minimize the mean wave amplitude beneath the drops at impact. Our work provides insight into the complex interactions and collective motions that arise in bouncing-droplet aggregates.