LAUSR

Dissolution-driven density instability (DI) occurs when a species A dissolves into a host fluid and introduces a buoyantly unstable stratification. Such an instability has positive effects in related applications and may be affected if species A reacts with solute B in the host fluid. In this paper, the lattice Boltzmann (LB) method is employed to simulate the dynamics of such an instability coupled with reaction A + B → C in porous media at the pore scale. Numerical simulations in homogeneous media have demonstrated that six types of dissolution-driven DI can be classified based on the Rayleigh numbers of three chemical species Rar (ratio of buoyancy to viscous forces), and reaction can accelerate, delay or even trigger the development of DI. Then, a parametric study has indicated that, increasing RaCB (RaC − RaB) can intensify density instability and reaction, promote the diffusion of species A, and also introduce either stabilizing or destabilizing effects of reaction. Besides, the increase of initial reactant concentration or/and Damköhler number Da (ratio of flow time to chemical time) can enhance the influence of chemistry. Finally, simulations are carried out in three types of heterogeneous media HE1–HE3, and six groups of fingering scenarios can also be observed in each medium. However, compared with the homogeneous case, heterogeneous media HE1 with randomly distributed solid grains can introduce deeper advancing position and rougher density fingering, and media HE2 and HE3 with vertical variations of pore spaces can affect the developing speed of fingering obviously. In terms of the storage of species A in the host fluid, medium HE2 with large pore size in the top layer is favorable. The present study is of significant importance for applications such as carbon capture and storage.