Mechanistic studies of capillary processes in porous media. Part 1.—Probabilistic description of porous media

Abstract

Prior to the proper study of any capillary process, it is absolutely necessary to describe correctly the porous medium in which the process is supposed to occur. This description can be made on the basis of a network consisting of alternate sites and bonds. The originality of the present treatment consists in introducing the following constraints, which are absent in netweks other than those which are porous in nature: for a porous network (i) to be self-consistent it must obey the ‘construction principle’, i.e. the size of any site must be greater or at least equal to the size of any of its delimiting bonds, and (ii) to be verisimilar the randomness in size-topology must be shared alike between sites and bonds and raised to a maximum. From these constraints there arise topological size correlations and statistical properties which are analysed in detail. Our description allows the construction of adequately porous networks by analytical (probabilistic), digital (Monte-Carlo) or analogical (micromodel) methods, which must all conform to the above constraints. In this part, emphasis is made on the probabilistic description. It appears that simple models used by previous authors, e.g. for treating capillary condensation and evaporation, are in fact extreme cases of ours, and some of them are revealed as unable to represent real media.