Combined wicking and evaporation of NaCl solution with efflorescence formation: The efflorescence exclusion zone

An experiment combining wicking and evaporation of a NaCl solution and leading to the formation of salt efflorescence is presented. The experiment shows that efflorescence develops over the porous medium surface exposed to evaporation except in the bottom region of the sample. This region remains free of efflorescence and is called the exclusion zone. It is shown that the exclusion zone extent depends on the solute concentration in the bottom reservoir. A model is developed, and it helps understand the exclusion phenomenon. The arch shape of the exclusion zone upper boundary is explained and modeled. The study is also seen as a successful test for the model of efflorescence growth driven by evaporation and salt precipitation presented in a previous study. The modeling approach is expected to help develop better models of salt transport with crystallization at the surface of porous media in relation with soil salinization issues or the salt weathering of porous materials

Gas injection in a liquid saturated porous medium. Influence of pressurization effects and liquid films

We study numerically and experimentally the displacement of a liquid by a gas in a two-dimensional model porous medium. In contrast with previous pore-network studies on drainage in porous media, the gas compressibility is fully taken account. The influence of the gas injection rate on the displacement pattern, breakthrough time and the evolution of the pressure in the gas phase due in part to gas compressibility are investigated. A good agreement is found between the simulations and the experiments as regards the invasion patterns. The agreement is also good on the drainage kinetics when the dynamic liquid films are taken into account