The transport behaviour of the haematocrit in the larger arteries is important in defining the variations in viscosityof blood. In this study, a finite volume method is used in order to simulate the blood flow and haematocrit transportthrough a large 3D human-like 90-degree bifurcation. The simulations are carried out to investigate the importance ofexplicitly modelling the non-Newtonian viscosity of blood regarding defining the flow. It is expected to be especiallyimportant in the regions surrounding a bifurcation. The main focus is to compare non-Newtonian to Newtonianbehaviour of the flow through important parameters such as pressure losses, mean viscosity variations and bulktransport properties of haematocrit. The study considers a broad range of physiological and pulsatile flow conditions,and displays the importance of modelling blood flow as a non-Newtonian fluid. The results have a relevant impactregarding the possible discrepencies in important physiological parameters such as wall shear stress (WSS), whencoupling the haematocrit field data back to the viscosity models.

Complex and slow interaction of different mechanical and biochemical processes in hemodynamics is believed to govern atherogenesis. Over the last decades studies have shown that fluid mechanical factors such as the Wall Shear Stress (WSS) and WSS gradients can play an important role in the pathological changes of the endothelium. This study provides further indications that the effects of fluid mechanical aspects are correlated with the diseased regions of the larger arteries. Unsteady high temporal WSS gradients (TWSSG), a function of the shear-thinning property of the non-Newtonian viscosity, move with the separation bubble. Red Blood Cell (RBC) dilution due to the secondary flows determines the magnitudes of the WSS and TWSSG. The results indicate that the focal nature of the TWSSG may have implications on the response of the endothelium.