Abstract
This paper presents a Computational Fluid Dynamics (CFD) model on the effect of capillary pressure on the retention behaviour of a granular material. The model proposes an unprecedented CFD insight into the onset of liquid menisci at the inter-particles contact under varying hydraulic conditions. The present work models the material grains as smooth spherical particles that define a porous network filled by two interstitial fluids: air and silicon oil. The numerical model has been subsequently validated against experimental measurements of the degree of saturation at different capillary pressures taken by Dullien et al. [F.A. Dullien, C. Zarcone, I.F. MacDonald, A. Collins, R.D. Bochard. J. Colloid Interface Sci. 127, 2 (1989)] in a system of smooth glass beads flooded with silicon oil. Results from the numerical simulations confirm the good capability of the model to reproduce the experimental retention behaviour of the granular material. Finally, the present paper laid the basis for future CFD studies on the effect of various factors (e.g. hydraulic hysteresis, surface roughness and/or grain shape) on the capillary pressure acting at the interparticle contact.
Highlights
The capillary actions that raise at the interfacial equilibrium between vapour and liquid, play a fundamental role in several physical phenomena: flow of granular materials, friction between surfaces, adhesion between particles or particles and surfaces [12]
The numerical model proposed in the present paper focuses on the retention behaviour of smooth glass beads flooded with silicon oil, as it will be described
The proposed model has been validated against the experimental data by Dullien et al [1] obtained on a pack of smooth glass beads flooded with silicon oil at different levels of capillary pressures
Summary
The capillary actions that raise at the interfacial equilibrium (i.e. meniscus) between vapour and liquid, play a fundamental role in several physical phenomena: flow of granular materials, friction between surfaces, adhesion between particles or particles and surfaces [12]. These phenomena are crucial in a very broad range of industrial and engineering applications, such as food industry, pharmaceutics, construction industry and agriculture to name a few. More recent techniques enabled instead an unprecedented visualisation of liquid menisci forming in unsaturated granular materials.
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