Speaker
Description
The subsurface is a complex fractured and/or porous system consisting of void spaces through which fluids can flow, and solid structures such as rocks pebbles and aggregates. There, water carries nutrients, dissolved and non-dissolved gases whose interactions with porous structures give rise to a plethora of processes including chemical reactions and colloidal filtration. The latter is central to many environmental processes (e.g. water treatment, soil contaminant removal, nutrient availability regulation, spread of pathogenic microbes and chemical reactions in the hyporheic zone of riverbanks).
Natural environments whose properties vary in space are characterised by structural heterogeneity and host the presence of more fluids that interact with each other. In un-saturated conditions not only the porous structure influences the flow and the transport, but also the fluids interfaces. At those phases interfaces (for instance between air and water) no slip boundary conditions affect the flow dynamics and can represent zones for adsorption and so colloidal retention. The spatial organisation of the fluid phases impacts the permeability of the system modifying the pressure distribution and the flow organisation. Moreover, the presence of air clusters can create dead-end pores/zones where no net flow occurs and transported substances can stagnate. The transport of colloids and bacterial cells through saturated porous media is often treated via the application of the classical colloid filtration theory (CFT, based on the seminal model of John Happel from 1958) which does not take into consideration the detailed structure of the porous system. Recently, new theories have been proposed to take into consideration the porous structure but only for saturated conditions cases. To investigate this phenomenon in un-saturated heterogeneous porous media, we design a microfluidics experimental setup with time-lapse video microscopy to trace the Breakthrough curves and deposition profiles while periodically monitoring the air clusters spatial distribution and their dynamics.
| Country | Switzerland |
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