Effects of Hematocrit and Non-Newtonian Blood Rheology on Pulsatile Wall Shear Stress Distributions in Vascular Anomalies: A Multiple Relaxation Time Lattice Boltzmann Approach

Hematocrit (Hct) is defined as the volume percentage of red blood cells in blood. Hct plays a crucial role in determining the viscosity of blood, and therefore flow patterns within the cardiovascular system. In the present study, a three-dimensional computational technique based on the lattice Boltzmann method (LBM) with a multiple relaxation time (MRT) collision operator is employed to investigate the effect of Hct on blood flow patterns, and wall shear stress (WSS) distributions under pulsatile conditions in vascular anomalies. To accurately represent the non-Newtonian, rheological properties of blood, we developed a constitutive model based on the Carreau-Yasuda model and available published experimental data, where the parameters in the model are a function of Hct. We analyze the numerical and physical aspects of the non-Newtonian MRT-LBM model, coupled with the proposed constitutive equation, to assess the accuracy and numerical stability of the present model and how it is affected by different Hct levels. Our results indicate that changes in Hct levels have a significant impact on flow dynamics in vascular anomalies. Elevated levels of Hct lead to increased oscillatory WSS variations. When the Hct level is increased, the response in the WSS distribution is non-linear. Also, pulsatile blood flow, combined with altered rheological properties due to Hct variations, affects WSS distribution in aneurysms and stenosis.