Study On Effects Of Dissolution/adsorption On Flows In Porous Media

Dissolution/adsorption-induced flows in porous media are frequently encountered issues in many industrail fields,such as the carbon dixoide sequestration,oil recovery,the removal of the pollutant in soil,and so on.The particular interest of this work is focused on the density driven flow with dissolution reaction in porous media and the transport of nanoparticles with aggregations in porous media.Due to the fact that the coupling of the flow,solute transport and the chemical reaction,investigations of these two problems are quite challenging.A better understanding of the effects of dissolution and adsorption on the flows is still in need.Therefore,we will conduct numerical simulations,linear stability analysis,as well as experiments to study the reactive transport in porous media to address this issue.For the reactive transport at the pore scale,we first develop a multi-relaxation-time lattice Boltzmann equation model as well as a boundary scheme for linear heterogenous reactions.A lattice Boltzmann equation model is then proposed for the Darcy-scale reactive flows.On the basis of these work,the dissolutioin/adsorption-induced flows in porous media are simulated using the developed lattice Boltzmann equation models and the boundary scheme.Furthermore,the linear stability analysis and the laboratory experiments are performed to validate the numerical results.The main points of this wok are as follows:1.As for the pore-sacle simulations,we first develop a multi-relaxation-time lattice Boltzmann equation model for reactive flows in porous media,which is validated to have superior numerical stabilty.This model is able to simulate the reactive transport with small viscosity/diffudion coefficient.Then,we further develop a boundary scheme for the linear heterogeneous surface reactions,which has been validated to have relatively high accuracy.Moreover,it can be implemented easily.The proposed lattice Boltzmann equation model as well as the boundary scheme are promising methods for the pore-scale study of the reactive transport.2.As for the Darcy-sacle simulations,a localized lattice Boltzmann equation model for reactive flows is developed,which is proven to have good numerical stability.It can be used to simulate the reactive transport with sufficiently small diffusion coefficient.This model fills the gap of the lattice Boltzmann method for simulating the Darcy-scale reactive flows.It is also an alternative method for simulating the Darcy-scale reactive transport in porous media.3.The density-driven flows with dissolution in porous media are studied using the proposed lattice Boltzmann equation models(both at pore and Darcy scales)as well as the boundary scheme.The numerical results show that the density contrast and the dissolution of the solid phase in porous media increase the instability in the system,while the heterogenous reaction can suppress the instability.The overall instability depends on the competitions among these three factors.The numerical results are then validated by the linear stability analysis.These results can help us to understand the transport of CO2 in the subsurface.4.Laboratory experiments are conducted to study the transport of nanoparticles in porous media.Aggregations are observed due to the small size of particles.The experimental results display that the aggregations increase the numbers of retained particles in porous media.Darcy-scale simulations confirm the experimental observations.In addition,porescale simulations reproduce the aggregation,transport and adsorption of particles in porous media,which provide explainations for the results of experiments and the Darcy-scale simulations.In summary,the proposed lattice Boltzmann equation models as well as the boundary scheme are useful tools for studies of the reactive transport in porous media.In addition,we address the effects of dissolution and adsorption on the solute transport in porous media based on the numerical/theoretical/experimental results.The results presented in this work can be used to fileds such as the carbon dixoide sequestration,oil recovery,the removal of the pollutant in soil,and so on...