Modeling Blood Flow Through Intracranial Aneurysms: A Comparison of Newtonian and Non-Newtonian Viscosity

The effect of non-Newtonian blood flow on the value of wall shear stress (WSS) of an intracranial aneurysm was investigated using computational fluid dynamics. For cerebral arteries, blood is often assumed to behave as a Newtonian fluid, though the effects of non-Newtonian flow on the prediction of areas of low WSS associated with aneurysm rupture are not clear. Geometry was based on published data and a Newtonian model validated against experimental results. Newtonian, unrestricted non-Newtonian, and viscosity-limited non-Newtonian models were compared under pulsatile conditions. Peak WSS of the Newtonian model was 28.7 Pa, and the lowest value of peak WSS for the unrestricted non-Newtonian models was 16.5 Pa. Viscosity-limited non-Newtonian models predicted flow velocity and WSS similar to those predicted by the Newtonian model in high-shear-rate regions, though maximum areas of critically low WSS were up to 42 % smaller than those predicted by the Newtonian model. In conclusion, viscosity limits are required to prevent excessive thinning of non-Newtonian models and the effects of non-Newtonian viscosity are significant for blood flow within low-shear-rate regions of an intracranial aneurysm.