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

Abstract

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/Ra², 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.