Dynamics of Miscible Nanocatalytic Reactive Flows in Porous Media

Nanocatalysts with their unique properties play an increasingly crucial role in areas ranging from energy and the environment to medical sciences. Despite numerous experimental studies on the utilization of nanocatalysts, there is a lack of theoretical understanding about the effectiveness of nanocatalyst application in porous media. In this study, we conduct both linear stability analysis (based on Quasi-Steady-State approximation) and nonlinear numerical simulations (based on a pseudospectral technique) to investigate mixing and in situ conversion of a reactant in the presence of nanocatalysts. Using the linear stability analysis, we parameterize the role of the in situ conversion on the stability of the system. Characterization of the nanocatalyst efficiency in terms of the degree of mixing and in situ conversion rate of the reactant is also performed through nonlinear numerical simulations. Our results show that while the increase of the nanocatalyst log mobility ratio attenuates the instabilities at the displacement front, the progress of the nanocatalytic reaction demonstrates a destabilizing effect. It is also seen that the nanocatalyst deposition leads to the rise of two competing mechanisms, the interplay of which controls the dynamics of miscible nanocatalytic reactive flows in porous media. Moreover, we introduce the effective penetration depth of nanocatalysts in porous media. Results reveal the crucial role of viscous fingering for increasing the reaction rate and indicate how the injected nanocatalysts lose their effectiveness due to their deposition in porous media. This study provides new insight into the application of nanocatalysts in porous media.