Department of Chemical Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
Phys Rev E. 2017 May;95(5-1):052803. doi: 10.1103/PhysRevE.95.052803. Epub 2017 May 22.
We study the thinning and drainage of the intermediate liquid film between a bubble and a solid surface at close proximity in the presence of a surface acoustic wave (SAW) in the solid. Specifically, we employ the diffraction of light to observe a long air bubble confined in a solid rectangular channel filled with silicone oil. This setup, constituting a two-dimensional physical model of thin film drainage, allows us to analyze the influence of a SAW on the rate of thinning of the micron-thick liquid film separating the bubble and the solid substrate. The viscous penetration of the SAW into the liquid imposes a convective drift of mass, redistributing the fluid in the film against capillary resistance and producing a net drift of liquid out of the film. The rate of drainage of liquid from the film increases by one to several orders of magnitude in comparison to the rate of drainage due to the Laplace pressure of the bubble alone. The experimental findings agree well with a newly developed theory describing the SAW-enhanced drainage as a competition between the capillary flow and SAW-induced streaming.
我们研究了在固体中存在表面声波（SAW）时，靠近固体表面的气泡和固体之间的中间薄液膜的变薄和排出。具体来说，我们利用光的衍射来观察一个被限制在固体矩形通道中的长气泡，该通道充满硅油。这种设置构成了薄膜排水的二维物理模型，使我们能够分析 SAW 对分离气泡和固体基底的微米厚液体薄膜变薄速度的影响。SAW 粘性地渗透到液体中会引起质量的对流漂移，从而在毛细阻力下重新分配薄膜中的流体，并产生液体从薄膜中净流出的漂移。与仅由气泡的拉普拉斯压力引起的排水速度相比，液体从薄膜中的排出速度增加了一个到几个数量级。实验结果与新开发的理论很好地吻合，该理论描述了 SAW 增强的排水是毛细流和 SAW 诱导的流动之间的竞争。
