Effect of hematocrit and rouleaux on apparent viscosity in capillaries

Abstract

Computational results are presented for a model of capillary blood flow consisting of red-cell shaped particles suspended in a Newtonian fluid. The red cells are assumed to be axisymmetrically located in a circular tube and to maintain their biconcave disk shape during the motion. The cells are equally spaced along the tube and the motion is assumed to be sufficiently slow to make inertial terms negligible. The results show that the apparent viscosity is linear in the hematocrit at low hematocrits, but increases less rapidly at high hematocrits due to trapping of fluid between cells. The effect of rouleaux is to slightly decrease the apparent viscosity. The most important parameter in determining the apparent viscosity is the ratio of the diameter of the red cells to capillary diameter.