Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey 07114, United States.
Department of Computer Science, Cornell University, Ithaca, New York 14853, United States.
Langmuir. 2023 Mar 14;39(10):3645-3655. doi: 10.1021/acs.langmuir.2c03273. Epub 2023 Feb 28.
In this study, we numerically investigate the dynamic behaviors of micron-scale compound droplets impacting onto superhydrophobic surfaces patterned by micropillar arrays using a three-dimensional free-energy-based lattice Boltzmann method. We address how the interplay between physical parameters (i.e., Weber number) and geometric parameters (i.e., pillar density and spacing and the droplet core-shell size ratio) affects the spreading, breakup, and rebound behaviors of compound droplets, which remains unknown and unquantified. We identify three flow regimes in which the interfacial morphology between the core and shell evolves and breaks up in distinct ways: namely, hole nucleation at the substrate, rupture of the film at the apex of the shell, and toroidal formation of the core droplet before its detachment from the pillars. We demonstrate that the transition between the three regimes and the maximum spreading factor of compound droplets can be changed by varying the core-shell size ratio, the pillar density, and the Weber number. The non-wetting behavior of the pillar structures eventually forms a new suspended pure droplet or a new suspended compound droplet, which can be characterized by the core-shell size ratio, pillar density, and Weber number.
在这项研究中，我们使用基于三维自由能的格子玻尔兹曼方法数值研究了微米级复合液滴冲击超疏水表面微柱阵列图案的动力学行为。我们研究了物理参数（如韦伯数）和几何参数（如支柱密度和间距以及液滴核壳尺寸比）之间的相互作用如何影响复合液滴的扩展、破裂和回弹行为，而这些行为仍然未知和未量化。我们确定了三个流动区域，其中核和壳之间的界面形态以不同的方式演变和破裂：即在基底处形成空穴、在壳的顶点处破裂以及在核心液滴从支柱上脱离之前形成环形核心液滴。我们证明，通过改变核壳尺寸比、支柱密度和韦伯数，可以改变三种流动区域之间的转变和复合液滴的最大扩展因子。支柱结构的非润湿行为最终形成了新的悬浮纯液滴或新的悬浮复合液滴，这可以通过核壳尺寸比、支柱密度和韦伯数来表征。
