(142de) Effect of Polymer Additives On Blood Flow in the Microcirculation: Simulations and Theory

In recent experimental studies, it has been shown that introducing drag reducing polymers (DRP) to blood in nanomolar concentration has many beneficial physiological effects, including the prevention of lethality from hemorrhagic shock in animals. In micro-channel experiments, with suspensions of red blood cells (RBCs), DRPs have been shown to reduce cell free layer thickness and affect the orientation of the cells. The underlying mechanisms for these phenomena are still not understood. In the present study, we investigate the dynamics of RBCs in Newtonian fluids and in dilute solutions of DRP in microcirculation. Cell membranes are modeled with energy penalty for area changes and bending. Polymer molecules are modeled as bead-spring chains with finitely extensible nonlinearly elastic springs. Three dimensional simulations are performed with a novel Stokes flow formulation of the immersed boundary method for the capsules, combined with Brownian dynamics for the polymer molecules. We present our study for a range of microchannel diameter, from arterioles and venules which are 30-75 μm in internal diameter to capillaries which are few microns in diameter. For larger channel, we report migration of RBCs, cell free layer thickness, apparent viscosity, pressure drop and wall shear stress in microcirculation with and without DRPs. In capillary scale channel, we report the shape transitions and dynamics of RBC and the effect of elasticity and bending rigidity of membrane and the effect of adding polymers.