Wetting effects on the spreading of a liquid droplet colliding with a flat surface: Experiment and modeling

Abstract

In this paper an experimental and theoretical study of the deformation of a spherical liquid droplet colliding with a flat surface is presented. The theoretical model accounts for the presence of inertia, viscous, gravitation, surface tension, and wetting effects, including the phenomenon of contact-angle hysteresis. Experiments with impingement surfaces of different wettability were performed. The study showed that the maximum splat radius decreased as the value of the advancing contact angle increased. The effect of impact velocity on droplet spreading was more pronounced when the wetting was limited. The experimental results were compared to the numerical predictions in terms of droplet deformation, splat radius, and splat height. The theoretical model predicted well the deformation of the impacting droplet, not only in the spreading phase, but also during recoiling and oscillation. The wettability of the substrate upon which the droplet impinges was found to affect significantly all phases of the spreading process, including the formation and development of a ring structure around the splat.

Mixing and internal dynamics of droplets impacting and coalescing on a solid surface

“…However, modeling flows with moving contact lines, particularly in 3D, is very challenging. In addition to the computational resource issue associated with capturing 3D time-dependent flow, the crucial difficulty with most simulation methods, for example, the popular volume-of-fluid (VOF) approach, is that the dynamic contact angle needs to be prescribed, often in a complicated fashion [30][31][32][33], dependent on experimental measurements. Simulations of flows such as the impact and spreading of droplets are particularly sensitive to the dynamic contact angle behavior.…”

Pyramidal and toroidal water drops after impact on a solid surface

“…For example, in the development of technology for liquid-metal microdroplet deposition (Fukai et al 1995), the 'wet' condition is desired. …”

A mesh-dependent model for applying dynamic contact angles to VOF simulations

“…Methods that explicitly track an interface (e.g. [18][19][20]) require a slip condition for the mesh node at the contact line. On the other hand, most VOF implementations (and more generally, most interface capturing techniques) utilize cell face normal velocities to advect volume fractions (e.g.…”