Hydrology, vadose zone research, petroleum engineering and many other related disciplines require a detailed description of flow and transport processes in porous media on scales ranging from meters to kilometers. All existing continuum Darcian-scale models that are presently used to solve such problems rely on effective flow properties and representative elementary volume (REV) concepts. The validity of such concepts has recently been questioned. Flow and transport model parameterization is usually performed using limited sampling and laboratory measurements, or statistical approaches such as, for example, pedotransfer functions. Usually parameterization assumes existence of a REV, extrapolation of undisturbed soil and rock core measurements to larger modelling blocks, and transport described by the advection-dispersion equation (ADE) and related approaches. These assumptions are recently being shown not to hold for real complex soil and rock formations. Pore-scale modelling approaches, on the other hand, provide a possibility to study flow and transport properties of porous media using first principles without aforementioned assumptions. The limitation is that it is mostly not feasible to apply pore scale imaging and modelling on domains of relevant sizes. This notion brings an understanding that both pore-scale and continuum-scale models should be combined to properly describe multi-scale flow and transport problems in porous media. However, at this point it is not clear how this could be effectively done. Owing to recent developments in imaging technologies, e.g., X-ray micro-tomography, BIB/FIB-SEM and others, we can now potentially obtain robust multi-scale structural information on any soil or rock sample. If appropriate structure-property relationships can be found for broad ranges of porous media types using pore-scale modelling approaches, then this information may be used to parameterize continuum scale models based on local soil structure surveys. Morphological and statistical descriptors of soil structure such as Minkowski functionals, correlated pore-size distributions and spatial correlation functions may serve as a base for measuring multi-scale variability of soil structure and to create continuum model parameters by previously established structure-property relationships.
This Session aims to bring together researchers working on soil structure characterization, and pore-scale and continuum scale modelers of flow and transport. Topics of potential interest include, but are not limited to:
- how to effectively obtain multi-scale solid phase soil structure information via imaging tools such as X-ray tomography and related techniques;
- how to convert 3D structural information into mathematical descriptors that can describe and store any complex soil structure;
- mechanistic and statistical reconstruction methods (multiple-point statistics, correlation functions, process-based models) to describe/generate or re-create 3D soil structure from limited information such as 2D cross-perpendicular cuts, grain-size distributions, etc.;
- pore-scale modelling techniques to simulate single and multi-phase flow (LBM, SPH, FVM/FEM, pore-network models) in porous media to obtain effective flow and transport properties based on 3D pore geometries (permeability, relative permeabilities, dispersion, gas diffusion; etc.);
- REV analysis of complex soil structures, influence of heterogeneities on upscaling of single and two-phase flow properties;
- influence of preferential flows and fractures on flow and transport in heterogeneous soils inferred from pore-scale simulations, as opposed to dual-continuum/porosity and other related approaches;
- parameterization of continuum Darcian scale models (Richards’ equation, ADE, two-phase flow Darcy’s equation, etc.) using pore-scale modelling on 3D pore geometries or soil structural information.