Numerical study on the dynamic behaviors of shear-thinning droplets impacting on a hydrophobic spherical surface

Abstract

In this study, the dynamic behavior of shear-thinning droplets impacting on a hydrophobic spherical surface is numerically investigated using the volume of fluid method coupled with dynamic contact angle and a power-law model. The differences in dynamic behaviors between shear-thinning and Newtonian droplets are first studied. By analyzing the distribution of pressure and shear rate inside the droplet, it is found that the shear-thinning behavior of the droplets leads to an uneven distribution of apparent viscosity upon impact, which in turn prevents droplet rebound. The effects of various impacting conditions, such as apparent viscosity, impact velocity, surface tension and dynamic contact angle, on the spreading factor and liquid film thickness of shear-thinning droplets are investigated. According to the behaviors of droplets, the impacting process can be divided into three phases: (I) initial deformation, (II) inertia-dominated, and (III) viscosity-dominated phases. In order to reveal the physical mechanisms that prevent shear-thinning droplets from rebounding on the hydrophobic particle surface, the conversion of kinetic energy, viscous dissipation, surface energy, and potential energy during the three phases of the impact process is also analyzed in detail.