Pore-scale modelling and tomographic visualisation of drying in granular media

Area of Science:

• Porous media physics
• Fluid dynamics
• Materials science

Background:

• Understanding liquid phase dynamics in granular materials is crucial for processes like drying, wetting, and contaminant transport.
• The spatial evolution of liquid clusters and drying fronts at the pore scale influences macroscopic drying rates and patterns.

Purpose of the Study:

• To investigate the spatio-temporal evolution of liquid clusters during the drying of granular media.
• To determine the effect of the contact angle on the drying front's dispersion.
• To analyze the relationship between microstructure and gas-liquid interfacial area during drying.

Main Methods:

• Utilized X-ray microtomography to visualize the 3D distribution of solid, liquid, and gas phases in granular assemblies.
• Dynamically tracked the propagation of liquid menisci through the porous structure.
• Performed direct numerical simulations on a digital representation of the experimental porous medium.

Main Results:

• Observed that a sharper drying front forms with silanised (less hydrophilic) particles compared to untreated (hydrophilic) particles.
• Numerical simulations confirmed that the contact angle significantly influences the degree of drying front dispersion.
• Simulations revealed a strong dependence of the average gas-liquid interfacial area on the contact angle within the porous microstructure.

Conclusions:

• The contact angle is a critical parameter controlling drying front morphology and liquid cluster dynamics in granular media.
• X-ray microtomography and numerical simulations provide complementary insights into pore-scale drying phenomena.
• Findings have implications for optimizing drying processes and understanding fluid transport in porous materials.