Efficient coupled lattice Boltzmann and Discrete Element Method simulations of small particles in complex geometries

Many interesting particulate flow problems can only be studied using efficient numerical methods. We present a method based on a lattice Boltzmann fluid coupled to unresolved particles that interact with each other via the Discrete Element Method. Our method improves upon existing numerical schemes through the addition of a novel subcycling algorithm that guarantees momentum conservation during each DEM substep. The intended application is studying transport of solid particles in physiologic processes, although the method is generally applicable. We present in detail the development and (parallel) implementation of the model and show how intricacies of the coupling scheme must be considered to avoid unphysical behavior and instabilities. The scalability of the code is tested on two modern supercomputers. We demonstrate the method's applicability to biomedical applications by simulating the injection and distribution of particles in an idealized liver vasculature.