The Effects Of Interfacial Reaction On Mixing Processes In Porous Media Based On Lattice Boltzmann Method

The complex mixing process of two reactive solutions with interfacial instabilities in porous media appears in various industrial and natural processes,such as greenhouse gas enhanced oil recovery,carbon dioxide storage,and biochemistry pharmacy.The investigation of such problems is also the scientific fronts in the fields of energy,environmental engineering and chemical engineering.However,due to the complex structure of porous media,as well as the coexistence of reaction,mixing and interfacial instabilities,the mechanisms of such process are still unclear.Therefore,the mechanistic study on this problem is of great significance in both scientific researches and engineering applications.In this thesis,we will present a first-ever pore-scale numerical and analytical study on the reactive mixing process of two solutions with interfacial instability,and investigate the reaction effects on mixing process.The work is helpful for better understanding of the complex transport process in porous media,and provides a reliable predictive method for the related industrial applications.The main contents of this work include:1)A coupled lattice Boltzmann model for the reactive flow in porous media at pore scale is proposed,which can satisfy the industrial requirements of large Peclet number,large viscosity ratio and the unconnection between reaction and time step.In addition,the GPU algorithm is used to meet the computational efficiency.A series of tests are conducted and the results illustrate the high numerical stability and accuracy of the presented model.2)The viscous displacements between two reactive solutions in single pores are firstly studied.The transport details under different Peclet numbers,reaction rates and steady state concentrations are firstly studied in a non-periodic pore.The results show that the increase of Peclet number makes the reaction effects weaked,but the flow patterns are still similar.Specifically,the reaction can suppress the mixing process,which is even more obvious with increasing reaction rate;while the changes of the steady state concentration can influence the morphology of viscous fingering,but have little effects on the mixing process.The reaction-diffusion interface is then introduced into the simulations for a periodic pore.The influences of reaction are similar to that in the non-periodic case,and the conclusions are also verified based on the analytical solution.3)The reaction effects on mixing of two solutions with viscous fingering in porous media are then investigated at pore scale.When the interface between two fluids is initially set as a sharp one,the results show that the transport fashions under different porosities are similar with each other.It is also found that reaction can change the contents of two fluids and inhibit the mixing process significantly,which is also more obvious as the reaction rate increases.After that,the above problem is studied coupled with the reaction-diffusion interface.The transport details also follow the similar fashion even in different homogenous and heterogeneous porous media and under different parameters.The reaction and diffusion can reach an equilibrium condition under this specific interface.4)Finally a series of simulations about the density instability between two miscible reactive fluids are presented both in a single pore and porous media.The results show that the development patterns are similar under different parameters,and the reaction effects are basically consistent with that in the viscous fingering case.It is proved that the reaction can change the formation mechanisms of two kinds of interfacial instabilities and can inhibit the mixing process obviously.