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A new paradigm in modelling flow and transport in porous media: revisiting foundations of porous media science

Final Report Summary - SCIPORE (A new paradigm in modelling flow and transport in porous media: revisiting foundations of porous media science)

How can one model two-phase flow while taking into account the real and complex geometry of a granular material? How about a fibrous material? How fluid phases invade the pore spaces? How can we improve performance of products such as paper in inkjet printing, diapers, or fuel cells? These are essential questions which require a profound understanding of movement of air and a liquid in porous media. Up to now, our models of porous media systems have been unable to adequately answer these questions. Standard theories of two-phase flow have been deficient in explaining and predicting many observations.
In this project, we have used a combination of theoretical, computational, and experimental research to establish more physically-based models of porous media in order to address complex processes mentioned above. Based on thermodynamic principles, we have identified two state variables for describing two-phase flow in a porous material: volume of fluids occupying the pores (quantified by fluid saturation) and amount of interfaces that separate fluids (quantified by the specific fluid-fluid interfacial area).
We have employed various advanced imaging instruments, such as a confocal laser microscope, a scanning electron microscope, a computer tomography scanner, and digital cameras, in order to get high-resolution images of the pore space and the distribution of fluids there. We have developed numerical computer models for calculation of the fate of fluids in such systems. The quality of these models have been checked and improved through comparison to experimental results. We have studied flow processes in three real porous media in detail: i) paper and penetration of ink into it, ii) layers of diaper and infiltration of water through them, and iii) sandy soil and water flow through it. We have shown that the new model including the interfacial area is capable to predict the experiments carried out in paper and diapers relatively well.
We have shown that discontinuous globules of a non-wetting surrounded by a flowing wetting phase will become mobilized when the velocity of the wetting phase becomes larger than a critical value.
We have shown that the space between layers in a stack of think porous layers cannot be modelled by current macroscale models of two-phase flow. Our new modelling approach, called Reduced Continua mode is able to simulate the pore space between layers very well, particularly at low water saturations and slow imbibition and drainage processes.