Abstract
Liquid penetration analysis in porous media is of great importance in a wide range of applications such as ink jet printing technology, painting and textile design. This article presents an investigation of droplet impingement onto metallic meshes, aiming to provide insights by identifying and quantifying impact characteristics that are difficult to measure experimentally. For this purpose, an enhanced Volume-Of-Fluid (VOF) numerical simulation framework is utilised, previously developed in the general context of the OpenFOAM CFD Toolbox. Droplet impacts on metallic meshes are performed both experimentally and numerically with satisfactory degree of agreement. From the experimental investigation three main outcomes are observed—deposition, partial imbibition, and penetration. The penetration into suspended meshes leads to spectacular multiple jetting below the mesh. A higher amount of liquid penetration is linked to higher impact velocity, lower viscosity and larger pore size dimension. An estimation of the liquid penetration is given in order to evaluate the impregnation properties of the meshes. From the parametric analysis it is shown that liquid viscosity affects the adhesion characteristics of the drops significantly, whereas droplet break-up after the impact is mostly controlled by surface tension. Additionally, wettability characteristics are found to play an important role in both liquid penetration and droplet break-up below the mesh.
Highlights
Droplet impact onto solid, dry surfaces is a widely studied phenomenon, which has been extensively investigated in the past decades due to its involvement in many environmental and industrial applications [1,2]
Many experimental investigations have studied the effects of wettability on the droplet outcome after the impact, through the dynamic contact angle (DCA) values of the liquid-gas interface with the solid surfaces [6,7]
It was concluded that the receding contact angle and the contact angle hysteresis are important wetting parameters for the droplet impact dynamics both at the beginning and recoiling phases of the droplet
Summary
Dry surfaces is a widely studied phenomenon, which has been extensively investigated in the past decades due to its involvement in many environmental and industrial applications [1,2]. For small Re values the degree of change of the momentum of the droplet, due to viscous effects outside the substrate starts to become more significant, resulting in a reduction of the lateral spreading In addition it was found, that the potential penetration or absorption of the droplet into the porous surface will influence the impact dynamics. Liwei et al [23] utilised a 3D Many-Body Dissipative Particle Dynamics (MDPD) model and tested it against experiments of droplet impact on mesh screens They found good agreement between the numerical and experimental results, and concluded that the influence of the droplet speed and size of the mesh is of higher importance, compared to the wettability characteristics and the drop viscosity. This information offers additional insight into the complex underpinning mechanisms in the considered droplet impact phenomena
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