  The study of viscous fluid flow coupled with rigid or deformable solids has
many applications in biological and engineering problems, e.g., blood cell
transport, drug delivery, and particulate flow. We developed a partitioned
approach to solve this coupled Multiphysics problem. The fluid motion was
solved by Palabos (Parallel Lattice Boltzmann Solver), while the solid
displacement and deformation was simulated by LAMMPS (Large-scale
Atomic/Molecular Massively Parallel Simulator). The coupling was achieved
through the immersed boundary method (IBM). The code modeled both rigid and
deformable solids exposed to flow. The code was validated with the Jeffery
orbits of an ellipsoid particle in shear flow, red blood cell stretching test,
and effective blood viscosity flowing in tubes. It demonstrated essentially
linear scaling from 512 to 8192 cores for both strong and weak scaling cases.
The computing time for the coupling increased with the solid fraction. An
example of the fluid-solid coupling was given for flexible filaments (drug
carriers) transport in a flowing blood cell suspensions, highlighting the
advantages and capabilities of the developed code.
