(266i) Numerical Simulation of Cross-Flow Margination of Platelets in Small Vessels

The adhesion of platelets to the vascular walls is the first step in wound healing. During this process, the cross-flow margination of platelets blood flow is an important contributing factor as it promotes the preferential platelet concentration in the near wall region and hence the platelet adhesion rate. However, the actual mechanism of margination, as well as the dependence of margination time scales on flow parameters, is not well understood. As the red cells are the major constituents of blood, the knowledge of the hydrodynamic interactions between red cells and platelets is essential for understanding margination. We present a Stokes flow boundary integral formulation and complete simulations of the multiparticle red cell/platelet system in confined vessel geometries, with red cell membrane elasticity modeled by the well-known Skalak model and platelets modeled as rigid discoids. The cross-flow margination is shown to be diffusive process, where the diffusivity is induced by the cellular flow velocity fluctuations and analogous to the shear induced diffusivity in particulate flow. However, the process is very inhomogeneous owing the strong variation of the velocity fluctuations across the vessel and moreover, the RBC deformation is clearly important in creating the associated ?granular temperature? which promotes platelet margination. Thus, the dependence on flow shear rate, red cell hematocrit, and vessel geometries is quite interesting and will be discussed in detail.