Spreading of a droplet impacting on a smooth flat surface: How liquid viscosity influences the maximum spreading time and spreading ratio

Abstract

Existing energy balance models, which estimate maximum droplet spreading, insufficiently capture the droplet spreading from low to high Weber and Reynolds numbers and contact angles. This is mainly due to the simplified definition of the viscous dissipation term and incomplete modeling of the maximum spreading time. In this particular research, droplet impact onto a smooth sapphire surface is studied for seven glycerol concentrations between 0% and 100%, and 294 data points are acquired using high-speed photography. Fluid properties, such as density, surface tension, and viscosity, are also measured. For the first time according to the authors' knowledge, we incorporate the fluid viscosity in the modeling of the maximum spreading time based on the recorded data. We also estimate the characteristic velocity of the viscous dissipation term in the energy balance equation. These viscosity-based characteristic scales help to formulate a more comprehensive maximum droplet spreading model. Thanks to this improvement, our model successfully fits the data available in the literature for various fluids and surfaces compared to the existing models.

Maximum Spreading of Hydrofluoroether Drop Impacting on a Smooth Surface

“…Tian and Chen concluded that the surface tension had a greater impact on β max compared to viscosity, based on experimental data of liquids with viscosities ranging from 0.32 to 1.08 mPa·s. However, by comparing the drop spreading of water (μ = 1.0 mPa·s) and glycerol (μ = 1021.5 mPa·s), Aksoy et al reported that the effect of viscosity on β max could not be neglected. Based on the above results, the importance of the viscosity effect is different for different viscosity ranges.…”

Role of Nanoparticles in Nanofluid Droplet Impact on Solid Surfaces

“…The result from the impact of a droplet on a solid substrate can be categorized as spreading, splashing, or bouncing. The specific case arises from the competition between inertia, interfacial tension, and viscous forces. , These can be decomposed into the influence of several parameters: viscosity η, density ρ, surface tension σ, impact speed u 0 , and droplet diameter D 0 . In other words, the splashing threshold is characterized by Weber ( We = ρ D 0 u 0 2 / σ ) and Reynolds ( Re = ρD 0 u 0 /η) numbers incorporating inertia, viscous stress, and surface tension.…”

“…The specific case arises from the competition between inertia, interfacial tension, and viscous forces. 1 , 2 These can be decomposed into the influence of several parameters: viscosity η, density ρ, surface tension σ, impact speed u 0 , and droplet diameter D 0 . In other words, the splashing threshold is characterized by Weber ( ) and Reynolds ( Re = ρD 0 u 0 /η) numbers incorporating inertia, viscous stress, and surface tension.…”

“…The nanoparticle interactions and their position in the simulation would give hints on the occurrence of anticipated wetting and modified splashing conditions. These could then be incorporated into better modeling of the viscous dissipation term and evaluation of the competitive forces, as in Aksoy et al 2 …”

Simulation of droplet impact dynamics on V-shaped walls

“…They found that the droplet jetting time was inversely proportional to the impact velocity but the effect of wettability can be negligible. Aksoy et al (Aksoy, Eneren, Koos, & Vetrano, 2022) examined a droplet impacting a flat surface. They derived the maximum spreading ratio as a function of Weber number and Reynolds number (Re).…”