Acceleration of convective dissolution by chemical reaction in a Hele-Shaw cell

New laboratory experiments quantify the destabilising effect of a second-order chemical reaction on the fingering instability of a diffusive boundary layer in a Hele-Shaw cell. We show that, for a given chemical system, the dynamics of such a reactive boundary layer is fully determined by two dimensionless groups, Da/Ra-2, which measures the timescale for convection compared to those for reaction and diffusion, and C-Bo', which reflects the excess of the environmental reactant species relative to the diffusing solute. Results of a systematic study varying C-Bo' in the range 0-0.1 are presented. It is shown that the chemical reaction increases the growth rate of a perturbation and favours small wavelengths compared to the inert system. A higher concentration of C-Bo' not only accelerates the onset of convection, but crucially also increases the transport of the solute by up to 150% compared to the inert system. This increase in solute transfer has important practical implications, such as in the storage of carbon dioxide in saline aquifers.