Investigation of transport phenomena in porous structures containing three fluid phases

The spatial distribution of three fluid phases inside pore structures is determined through the minimization of total interfacial energy. A modified simulated annealing scheme is used for the determination of the optimal configuration rendering the method efficient at low saturations. The study in a further step of the distributions of the fluid phases in single and multipore domains indicates that the combination of the digital reconstruction with the annealing-based technique can adequately represent those multiphase systems. The proposed method provides the basis for the future prediction of sorption and transport properties of porous materials filled with more than two fluid phases. In order to testify the method, the tracer diffusion in a random sphere packing filled by three fluid phases as well as the creeping flow of a fluid phase through the same porous structure when the pore space is occupied by two immobile fluid phases, are investigated. The effective diffusivities are computed by a random walk method. The relative permeabilities are determined through the solution of Stokes equations using a finite-difference scheme in conjunction with the artificial compressibility relaxation algorithm. It is found that the aforementioned transport properties of the wetting and the non-wetting phases are in a good agreement with pertinent literature data and also are independent of whether the pore space is occupied by two or three fluid phases. The former reinforces the reliability of the proposed fluid-phase distribution technique. For both effective diffusivities and relative permeabilities, a number of very useful empirical equations, when only one fluid phase is conducting, are generated.