Dissolution in anisotropic porous media: Modelling convection regimes from onset to shutdown

In the present study, we use direct numerical simulations to examine the role of non-isotropic permeability on solutal convection in a fluid-saturated porous medium. The dense solute injected from the top boundary is driven downwards by gravity and follows a complex time-dependent dynamics. The process of solute dissolution, which is initially controlled by diffusion, becomes dominated by convection as soon as fingers appear, grow, and interact. The dense solute finally reaches the bottom boundary where, due to the prescribed impermeable boundary, it starts filling the domain so to enter the shutdown stage. We present the entire transient dynamics for large Rayleigh-Darcy numbers, Ra, and non-isotropic permeability. We also try to provide suitable and reliable models to parametrize it. With the conceptual setup presented here, we aim at mimicking the process of liquid CO2 sequestration into geological reservoirs.