Fluid Mechanics Seminar: Duncan R. Hewitt

Convective flow in porous media can be found in numerous geophysical and industrial processes, and has recently been investigated in the context of geological CO_2 sequestration. I will present high-resolution numerical simulations of statistically steady high-Rayleigh-number convection in a porous medium that is heated at the base and cooled at the upper surface. I will discuss the relationship between the strength of convection, as described by the Rayleigh number, and the transfer of buoyancy, as described by the Nusselt number. I will examine the remarkable dynamical structure of high-Rayleigh-number porous convection: the structure is characterized in the interior by ordered vertical columnar exchange flow with a regular (Rayleigh-number dependent) horizontal wavenumber k(Ra), and near the boundaries by vigorous short-wavelength boundary-layer instabilities . I will investigate the physical control of this structure by performing a stability analysis of the interior columnar flow: the predictions of this analysis give good agreement with the measured horizontal wavenumber k(Ra). Numerical results will be presented in both two-dimensional and three-dimensional porous media. I will then extend these results to consider the more physically relevant context of convection from below one boundary only, and consider the implications of these results for the long-term storage capacity of underground water-saturated porous rocks into which CO_2 has been injected.