New Hybrid Pore-Scale Simulation Method to Characterize Nanoparticle Transport, Aggregation, and Attachment Behaviors

To facilitate the applications of nanoparticles (NPs)for enhancinghydrocarbon production, it is important to understand the transportand attachment behaviors of NPs on a microscopic scale. A novel, hybridpore-scale simulation method using lattice-Boltzmann (LB) coupledwith Langevin-dynamics (LD) is proposed to investigate the transportmechanism of nanoparticles in a microchannel. The LD method is developedto characterize the physics of Brownian motion, thermal fluctuation-dissipation,multi-body hydrodynamics, and particle-particle interactions.A discrete LB forcing source distribution is employed to couple withLD. The random force of NPs, friction force of NPs, van der Waalsforce, as well as the electrostatic force between NPs and the microchannelare quantified in this Euler-Lagrange method to more accuratelysimulate the transport and attachment of NPs. Various examples (i.e.,single particle relaxation in viscous flow, Brownian motion in thedilute colloid system, and the attachment efficiency of NPs onto channelsurface) are implemented to verify the LB-LD method. The controllingfactors (i.e., ionic strength, particle diameter, and Reynolds number)are investigated in the attachment process of NPs. The NP with intenseBrownian diffusion and weak hydrodynamic effect is prone to have betterattachment efficiency. It is observed that a maximum value of attachmentefficiency exists as the ionic strength increases to about 0.01 M.Moreover, the ionic strength of the aqueous phase exerts significantimpact on the transport behavior of NPs: when the ionic strength isless than 0.005 M, an ordered structure of NP suspensions is formeddue to the dominance of electrostatic repulsion force; varying structuresof NP suspension are observed with the increase of ionic strength,and when the ionic strength is more than 0.01 M, a clustered structureof NP suspensions is formed by the dominance of van der Waals force.To quantitatively characterize the structure of NP suspensions undervarying conditions, a general phase diagram including three flow patterns(isolated, transitional, and clustered regime) is first proposed forNP suspension with specified ionic strength and Reynolds number. Theoutcomes of this work provide valuable insights into the criticalimportance of particle size, ionic strength, and hydrodynamic effectson the attachment and transport of NPs in porous media.