Dipartimento di Fisica e Astronomia "G. Galilei" , Università di Padova , Via Marzolo 8 , I-35131 Padova , Italy.
Department of Physics , Durham University , DH1 3LE Durham , U.K.
Langmuir. 2018 Oct 30;34(43):12882-12888. doi: 10.1021/acs.langmuir.8b02370. Epub 2018 Oct 22.
We report the results of comprehensive experiments and numerical calculations of interfacial morphologies of water confined to the hydrophilic top face of rectangular posts subjected to vertical vibrations. In response to mechanical driving, an initially flat liquid channel is collected into a liquid bulge that forms in the center of the rectangular post if the acceleration exceeds a certain threshold. The bulge morphology persists after the driving is switched off, in agreement with the morphological bistability of static interfacial shapes on posts with large length-to-width ratios. In a narrow frequency band, the channel does not decay into a bulge at any acceleration amplitude, but displays irregular capillary waves and sloshing instead. On short posts, however, a liquid bulge can be dynamically sustained through vertical vibrations but quickly decays into a homogeneous channel after the external driving is stopped. To explain the dynamic bulging of the liquid interface, we propose an effective lifting force pulling on the drop's slowly moving center of mass in the presence of fast oscillation modes.
我们报告了综合实验和数值计算的结果，研究了受垂直振动影响的亲水矩形柱顶面约束水的界面形态。在机械驱动的作用下，如果加速度超过一定阈值，最初平坦的液体通道会被收集到矩形柱中心的液体凸起中。在驱动关闭后，凸起形态仍然存在，这与具有大长径比的柱面上静态界面形状的形态双稳定性一致。在较窄的频率范围内，在任何加速度幅值下，通道都不会衰减成凸起，而是显示出不规则的毛细波和晃动。然而，在短柱上，通过垂直振动可以动态维持液体凸起，但在外部驱动停止后，凸起会迅速衰减成均匀的通道。为了解释液体界面的动态凸起，我们提出了一种有效的提升力，在快速振荡模式存在的情况下，拉动液滴缓慢移动的质心。
