  We present a computational framework for modeling large-scale particle-laden
flows in complex domains with the goal of enabling simulations in medical-image
derived patient specific geometries. The framework is based on a
volume-filtered Eulerian-Lagrangian method that uses a finite element method
(FEM) to solve for the fluid phase coupled with a discrete element method (DEM)
for the particle phase, with varying levels of coupling between the phases. The
fluid phase is solved on a three-dimensional unstructured grid using a
stabilized FEM. The particle phase is modeled as rigid spheres and their motion
is calculated according to Newton's second law for translation and rotation. We
propose an efficient and conservative particle-fluid coupling scheme compatible
with the FEM basis that enables convergence under grid refinement of the
two-way coupling terms. Efficient algorithms for neighbor detection for
particle-particle collision and particle-wall collisions are adopted. The
method is applied to a few different test cases and the results are analyzed
qualitatively. The results demonstrate the capabilities of the implementation
and the potential of the method for simulating large-scale particle-laden flows
in complex geometries.
