Process-based characterization of flow in unsaturated fractured rocks

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Simulation of rapid flow through unsaturated fractured rocks is still a challenge because of a number of uncertainties ranging from process understanding, scale effects and characterization of process parameters across scales. Our proposal focuses on the development of a modeling tool for simulation of unsaturated flow on a local scale and the assessment in how far small scale processes affect travel time distribution of water in unsaturated fractured rocks on larger scales. The main objective of model development is the simulation of free-surface flow including the effects of surface tension and contact line dynamics. For this purpose, meshless Smoothed Particle Hydrodynamics (SPH) codes will be developed. To obtain an understanding of flow processes that occur on fracture surfaces, simulations will cover a broad spectrum of flow regimes and interactions ranging from: (1) capillary flow, (2) thin adsorbed films on fracture surfaces, and (3) highly non-linear flow regimes in fractures, e.g. droplet flow. Modeling the complex hydrodynamic interplay between these flow compartments will strongly enhance the understanding of travel time distributions of water through fractured unsaturated rock materials, which cannot be captured with common volume effective continuum modeling approaches such as the Richards equation. The developed particle based flow models will provide a versatile numerical framework to investigate unsaturated flow through various porous materials and fracture geometries associated with consolidated rocks.