Dynamic Capillary Fringe: Flow and Transport Processes

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A dynamic capillary fringe (CF) poses a number of fundamental problems that originate in the transition from a continuous to a discontinuous and finally to a missing air phase. This apparently affects transport in the gas phase but also the very formulation of water flow which becomes strongly coupled with the air flow. In this sub-project, we want to (i) investigate the dynamics of the CF under transient forcing and assess the extent to which it may be represented by effective continuum properties, (ii) determine the formation and dissolution of a residual gas phase under transient forcing, and (iii) study dispersion phenomena in the water phase of the vadose zone, of the CF, and of the groundwater and in particular explore effective formulations for the three zones. The experiments will be run in Hele-Shaw cells and observed through light transmission, near-infrared imaging spectroscopy, and small tensiometer arrays. Full three-dimensional studies will be conducted in the central experimental facility of SP Z. In the second phase, transport of particulate matter will be studied as well as the impact of biofilms on flow and transport.