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Control of chemically driven convective dissolution by differential diffusion effects

par Jotkar, Mamta Raju ;De Wit, Anne ;Rongy, Laurence
Référence Physical Review Fluids, 6, 5, 053504
Publication Publié, 2021-05

Article révisé par les pairs

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Résumé :

Chemically driven convective dissolution can occur upon reaction of a dissolving species in a host phase when the chemical reaction destabilizes an otherwise stable density stratification. An A+B→C reaction is known to trigger such convection when, upon dissolution into the host solution, A reacts with B present in the solution to produce a sufficiently denser product C. We study numerically the effect of differential diffusion on such a chemically driven convective dynamics. We show that below the reaction front either double-diffusive or diffusive-layer convection can arise, modifying the local Rayleigh-Taylor instability. When B diffuses faster than C, the density profile contains a local maximum at the reaction front, followed by a local minimum below it. A double-diffusive instability can develop below the reaction front, accelerating the convective dynamics and thereby enhancing the dissolution rate of A into the host phase. Conversely, when B diffuses slower than C, the density profile exhibits a local maximum below the reaction front and diffusive-layer convection modes stabilize the dynamics compared to the equal diffusivity case. When B and C diffuse at equal rates but faster than A, the convective dynamics is accelerated with respect to the equal diffusivity case.