Reactive convective-dissolution in a porous medium: stability and nonlinear dynamics

We investigate the effects of a dissolution reaction, A(aq) + B(s) → C(aq), on the gravitational instability and nonlinear dynamic behaviour of a diffusive boundary layer in a porous medium. Our linear stability and numerical results reveal that, unexpectedly, even when the density contribution of the soluble product C is smaller than that of the dissolved solute A, the chemical reaction can destabilize the layer and accelerate the onset of convection. However, for a very light product, the reaction stabilizes the layer. We show that these widely disparate characteristics of the reactive-diffusive layer are outcomes of the nonlinear competition between two reaction effects, the destabilizing sharpening of the solute concentration gradient and associated increase in the solute diffusive flux, and the stabilizing replacement of the solute by a less dense product near the interface.