(248e) Dynamics of Suspensions of Elastic Capsules Flowing in Confined Geometries

Modeling the behavior of fluid-filled capsules (which can be considered as a simple representation of red blood cells and vesicles), is not only important to understand biological processes, such as blood flow in the microcirculation, but also to help design and improve microfluidic devices for characterizing or separating such particles.

The present work describes simulations of large numbers of deformable capsules with various properties in confined geometries. Our algorithm incorporates a General-Geometry-Ewald-Like method (GGEM) for efficiently calculating hydrodynamic interactions (O(N)) in an immersed-boundary method. This allows for a detailed description of the particle interface combined with a large degree of freedom to model the confining domain (grooved channels, cylindrical and spherical obstructions).

With our algorithm, we have addressed several issues. The ability to quickly simulate large number of particles enables examinations not only of the competition between shear-induced diffusion and wall-induced hydrodynamic migration of single particles, but also exploration of concentration effects and segregation by size, shape and/or deformability. The flow through a slit containing an array of pillars, which is a model representation of the interalveolar sheet structure of the capillaries in the lungs, has

been examined as well. Combined with the simulation of grooved channels, we propose a methodology to separate these cells depending on their deformability and size.

Finally, the effect of addition of long-chained polymer molecules in blood flow, known to lower blood pressure, is investigated.