表面张力
机械
气泡
材料科学
剪切流
剪切(地质)
流变学
毛细管作用
毛细管数
粒子(生态学)
流量(数学)
表面力
纳米技术
复合材料
热力学
物理
地质学
海洋学
作者
Milad Eftekhari,Karin Schwarzenberger,Sascha Heitkam,Aliyar Javadi,Aleksandr Bashkatov,Seher Ata,Kerstin Eckert
出处
期刊:Langmuir
[American Chemical Society]
日期:2021-11-02
卷期号:37 (45): 13244-13254
被引量:7
标识
DOI:10.1021/acs.langmuir.1c01814
摘要
The behavior of moving bubbles has mostly been studied in an axisymmetric flow field. To extend the knowledge to practical conditions, we investigate the interfacial and hydrodynamic properties of bubbles under asymmetric shear forces. Experiments are performed with a buoyant bubble at the tip of a capillary placed in a defined shear flow in the presence of surfactants, nanoparticles, and glass beads. The response of the interface to the surrounding asymmetric flow is measured under successive reduction of the surface area. Profile analysis tensiometry is utilized to investigate the dynamic surface tension and the surface rheology of the surfactant- and nanoparticle-laden interfaces. Microscopic particle image and tracking velocimetry are used to study the bulk flow and the interfacial mobility of the buoyant bubble. According to our results, the rotational component of the shear flow provokes an interfacial flow, which redistributes the adsorbed surfactants and particles at the interface. In the presence of NPSCs, a contiguous network of particles forms at the interface through densification of surface structures. We show that this interconnected nanoparticle network eventually stops the interfacial flow and decreases the mobility of the glass beads at the interface. The immobilization of the interface is characterized by a dimensionless number, defined as the ratio of the interfacial elasticity to bulk shear forces. This number provides an estimate of the interfacial forces required to impose interfacial immobility at a defined flow field. Our findings can serve as a basis to formulate boundary conditions for refined modeling and to predict the hydrodynamics of bubbles and droplets.
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