Numerical study on nonisothermal reactive viscous fingering

The numerical study examines the dynamics of viscous fingering in a miscible flow displacement involving an exothermic reaction between displacing and displaced fluids producing nanoparticles. The exothermic reaction alters fluid properties by producing nanoparticles and/or by releasing heat at the front, both competitive in nature. The front changes from stable to forward (reverse) fingering when the contribution of temperature (concentration) to the viscosity dominates. For a fixed viscous behavior, decreasing reaction rate weakens the forward movement of fingers and reverse fingering is obtained. For a fixed injection rate, the thermal diffusivity can weaken the thermal gradients leading to a stable displacement even when the system is viscously unstable and can also trigger double-diffusive instability in a viscously stable system. Overall, the study suggests that the interplay between the mass and thermal contribution to the fluid properties and chemical reaction rates governs the fingering dynamics.