Dynamic wetting of an occlusion after droplet impact. (February 2019)

• Record Type: Journal Article
• Authors: Rashidian, Hossein; Sellier, Mathieu; Mandin, Philippe
• Is Part Of: International journal of multiphase flow. Volume 111(2019)
• Page Start: 264
• Page End: 271
• Publication Date: 2019-02
• Subjects: Droplet impact -- Surface texture -- Hole formation -- Surface energy analysis -- Lattice Boltzmann method; Multiphase flow -- Periodicals; Écoulement polyphasique -- Périodiques; Multiphase flow; Periodicals; 620.1064
• DOI: 10.1016/j.ijmultiphaseflow.2018.12.002
• Languages: English
• ISSNs: 0301-9322

Abstract

Highlights: We present three-dimensional numerical simulations of a droplet impact on a substrate featuring an occlusion. The simulations, based on the Lattice–Boltzmann method, are validated against the Scheller and Bousfield correlation for normal droplet impact. We derive a criterion based on an energy balance which predicts whether the occlusion will rupture the lamella or not. Results show that rupture is more likely to appear as the diameter of the occlusion, the impact velocity, and the hydrophobicity of the substrate increase. Abstract: This paper investigates how and under which conditions the lamella of an impacting droplet is punctured by the presence of a small occlusion. Better understanding the conditions which lead to the rupture of the lamella is critical to produce defect free coating layers in the context of spray coating, for example. An analytical model based on surface energy analysis is proposed to obtain the critical thickness below which the liquid layer above the occlusion is unstable and lamella rupture occurs. Furthermore, we have developed a three dimensional multiphase lattice Boltzmann code to confirm the surface energy analysis and study the influence of key parameters like size of the occlusion, impact velocity and wettability of substrate on hole formation. Results show that a hole is more likely to appear as the diameter of the occlusion, the impact velocity, and the hydrophobicity of the surface increase. Graphical abstract: