Effect of wind turbulence on gas transport in porous media: experimental method and preliminary results

We demonstrate a novel experimental arrangement for measuring wind turbulence-induced gas transport in dry porous media under controlled conditions. This equipment was applied to assess the effect of wind turbulence on gas transport (quantified as a dispersion coefficient) as a function of distance to the surface of the porous medium exposed to wind. Two different strategies for the measurement of wind-induced gas transport were compared. Experiments were carried out with O2 and CO2 as tracer gases with average vertical wind speeds of 0.02–1.06 m s−1. Oxygen breakthrough curves as a function of distance to the wind-exposed surface of the porous medium were analysed numerically with a finite-difference-based model to assess gas transport. We showed that wind turbulence-induced gas transport is an important transport mechanism that can be 20–70 times larger than molecular diffusion-induced transport. Wind conditions and properties of the porous medium had strong controlling effects on this relationship. Importantly, we show that even though wind-induced gas transport is greatest near to the wind-exposed surface, it can have marked effects on the variation in gas concentration at much greater depths.