Effective kinetics and phases saturation impact on surface reactions in porous media

<p>Coupling of unsaturated flows and surface reactions, including sorption and desorption, takes place in environmental contexts such as soils and the unsaturated zone. Lower sorption coefficients than those observed from batch experiments are found in natural soils. However, a deep understanding of this coupling is missing. To achieve this objective, we designed microfluidics experiments and performed direct numerical simulations based on experimental images at the microscale. We explore the effects of fluid flow dynamics and reaction kinetics on the effective kinetics. We have observed that an increase in the air volume within the porous medium promotes more heterogeneous fluid flow velocities, controlling the mixing of the transported reactant and resulting in a non-monotonic effective kinetic of the surface reaction.</p>

Seepage and Groundwater Flow

Water in soil exists in a variety of forms, affects its engineering properties, and plays a very important role in all soil mechanics problems. The effects caused by the presence of water whether at rest or when moving through the pores of the soil must therefore be properly understood. Capillarity and both saturated and unsaturated flows are considered. Methods of measuring soil suction and the hydraulic conductivity of soils in the laboratory and in-situ are highlighted. The chapter considers the permeability of stratified deposits, effective stress, and seepage pressures. Using Darcy's law and other assumptions, the basic flow equation is derived. Analytical and graphical (flow nets) methods for solving the Laplace equation are developed. Kozeny's analysis of seepage through earth dam sections using the basic parabola is introduced and the Casagrande constructions are illustrated for some homogeneous earth dams with different discharge slopes. Seepage in soils with transverse isotropy and through soils with nonhomogenous sections are analyzed. The chapter ends with a consideration of the mechanics of piping, filter, and its design.