Simulating nanoscale suspension of particles and polymers using a coupled lattice-Boltzmann and Langevin-dynamics approach

A novel computational approach coupling the lattice-Boltzmann (LB) method and a Langevin-dynamics (LD) approach has been developed to simulate nanoscale suspensions in the presence of both thermal fluctuation and many-body hydrodynamic interactions (HI) with linear scalability. The dynamics of the suspended nanoscale particle/polymer (NPP) are resolved through the LD with the NPP Brownian motion explicitly driven by the stochastic force term. By introducing a discrete LB forcing source term, the LB method is coupled with the LD in a two-way fashion to directly include and resolve the many-body HI in the dilute regime. The validity and accuracy of this LB-LD approach are demonstrated through several verification problems, including velocity relaxation of an isolated particle, self-diffusion of a nanoparticle (NP) swarm, and relaxation of a single polymer chain. Good agreement between simulation and theory is observed. To ensure complete localization and linear scalability of the particle dynamics, an Eulerian host algorithm for efficient short-range pairwise particle search and interaction is introduced. Since the nanoscale suspension dynamics are intended to be fully resolved via sub-lattice techniques, this LB-LD approach can be favorably incorporated into complex multiscale computational frameworks for both biological and industrial multimodal suspension applications.