Liquid clustering and capillary pressure in granular media

By means of extensive lattice Boltzmann simulations, we investigate the process of growth and coalescence of liquid clusters in a granular material as the amount of liquid increases. A homogeneous grain–liquid mixture is obtained by means of capillary condensation, thus providing meaningful statistics on the liquid distribution inside the granular material. The tensile stress carried by the grains as a function of the amount of condensed liquid reveals four distinct states, with a peak stress occurring at the transition from a primary coalescence process, where the cohesive strength is carried mostly by the grains, to a secondary process governed by the increase of the liquid cluster volumes. We show that the evolution of capillary states is correctly captured by a simple model accounting for the competing effects of the Laplace pressure and grain–liquid interface.

References:

Delenne, J.Y., Richefeu, V. and Radjai, F., 2015. Liquid clustering and capillary pressure in granular media. Journal of Fluid Mechanics, 762. article preprint
Richefeu, V., Radjai, F. and Delenne, J.Y., 2016. Lattice Boltzmann modelling of liquid distribution in unsaturated granular media. Computers and Geotechnics, 80, pp.353-359.article

Capillary condensation from saturated vapor inside a 2D packing simulated by multiphase LBM