Development of flow and transport models and effective parameters for flow with dynamic boundary conditions

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This sub-project has two main goals. It builds up on the results from the first period, where an upscaled model for flow in heterogeneous media with large parameter contrasts was developed to describe the horizontally averaged water content of an infiltration front. The model was set up for conditions, where the horizontally averaged water pressure is not in equilibrium, which leads to a non-Richards type of model. In the first part of this project, we want to extend the work by addressing changes of flow regimes due to dynamic boundary conditions, which is relevant for flow close to the soil surface. In particular we want to focus on cycles of changing flow directions. Modeling concepts should be derived that allow a cross-over from equilibrium to non-equilibrium flow behavior. Also, the influence of dynamic boundary conditions on the properties of the displacement front on a meter scale will be analyzed. In the second part we want to extend the results for water flow to solute transport in a dynamic flow field. The focus will here also be on cycles of changing flow directions. The apparent advection, mixing and spreading of tracer plumes in heterogeneous media under dynamic flow conditions will be analyzed and macroscopic transport parameters will be derived. We will mainly use theoretical methods, but also carry out some laboratory experiments.