Spontaneous imbibition in disordered porous solids: a theoretical study of helium in silica aerogels

TL;DR

This theoretical study explores how helium liquid spontaneously imbibes in silica aerogels, revealing the influence of porosity on fluid dynamics, interface roughening, and the connection between imbibition and adsorption, with implications for interpreting experiments.

Contribution

It introduces a coarse-grained lattice-gas model combined with dynamical mean-field theory to analyze spontaneous imbibition in disordered porous solids, highlighting effects of porosity and wetting.

Findings

Imbibition front is always preceded by a precursor film.

Classical Lucas-Washburn law is generally recovered.

Interface roughening is affected by wetting and confinement.

Abstract

We present a theoretical study of spontaneous imbibition of liquid 4He in silica aerogels focusing on the effect of porosity on the fluid dynamical behavior. We adopt a coarse-grained three-dimensional lattice-gas description like in previous studies of gas adsorption and capillary condensation, and use a dynamical mean-field theory, assuming that capillary disorder predominates over permeability disorder as in recent phase-field models of spontaneous imbibition. Our results reveal a remarkable connection between imbibition and adsorption as also suggested by recent experiments. The imbibition front is always preceded by a precursor film and the classical Lucas-Washburn scaling law is generally recovered, although some deviations may exist at large porosity. Moreover, the interface roughening is modified by wetting and confinement effects. Our results suggest that the interpretation of the recent experiments should be revised.