On spread extent of sessile droplet into porous medium: Numerical solution and comparisons with experiments

Abstract

The spread of a wetting liquid sessile droplet into porous medium is solved numerically using the capillary network model with a microforce balance boundary condition at the liquid/gas free interface in the porous medium. The spread starts as the porous medium imbibes the sessile liquid, followed by liquid additionally being spread inside the porous medium itself. After there is no remaining sessile liquid, the net flow across the porous medium boundaries is equal to zero. Either spread, with or without sessile liquid present at the porous medium surface, is rendered by local differences in capillary pressure. These local differences are accounted for by implementing the numerical solution over a heterogeneous capillary network, consisting of pores connected by throats. Both pores and throats follow predefined distribution functions. Once there is no sessile liquid present on the porous medium surface, it is found from a numerical solution that the liquid front can extend significantly in time, wetting very large volumes of the porous medium. This is also measured in experiments, in which over time, an increase in wetted volume of more than 16 times is observed compared to the wetted volume right after the disappearance of sessile liquid on the porous medium surface. The numerical and experimental results for the time changes of ͑i͒ volume of liquid remaining at the porous medium surface, ͑ii͒ porous medium surface wetted area of the droplet imprint, and ͑iii͒ liquid protrusion depth into porous medium are compared, with very good qualitative and quantitative agreement found.

Fate of sessile droplet chemical agents in environmental substrates in the presence of physiochemical processes

“…The degradation took place under sealed conditions and was therefore modeled without evaporation. The model indicated VX disappearance and appearance of breakdown products in quantities similar to those reported in the experimental study [10].…”

“…Researchers in the past have solved the porous media flow by continuum or discrete methods. This volume of work has been addressed by Markicevic et al [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The flow through porous materials becomes more complicated when evaporation on the surface and within the pores is also present [15][16].…”

Wicking of a liquid bridge connected to a moving porous surface

“…removing oil droplets from a flat surface). Similarly, our model enables the prediction of the depth and radius of penetration of a contaminated droplet suspended on a flat surface and in contact with a moving porous material, which is relevant to the design of protection from chemical agents (Markicevic, D'Onofrio & Navaz 2010).…”

Dynamics of freely moving plates connected by a shallow liquid bridge

“…The dynamics of the solid bodies affects the droplet topology and will thus change the surface area in contact with the droplet and the pressure distribution within the liquid, thus affecting the spreading of contamination. 7 The forces applied by liquid bridges connected to static supporting surfaces were studied extensively. 8 However, in many applications it is common that at least one of the bodies is moving, and thus, the motion of the solid body may be influenced by the forces associated with the liquid bridge.…”