Non‐Newtonian blood flow study in a model cavopulmonary vascular system

Abstract

SUMMARYA transient haemodynamic study in a model cavopulmonary vascular system has been carried out for a typical range of parameters using a finite element-based Navier-Stokes solver. The focus of this study is to investigate the influence of non-Newtonian behaviour of the blood on the haemodynamic quantities, such as wall shear stress (WSS) and flow pattern. The computational fluid dynamics (CFD) model is based on an artificial compressibility characteristic-based split (AC-CBS) scheme, which has been adopted to solve the Navier-Stokes equations in space-time domain. A power law model has been implemented to characterize the shear thinning nature of the blood depending on the local strain rate. Using the computational model, numerical investigations have been performed for Newtonian and non-Newtonian flows for different frequencies and input pulse forms. The haemodynamic quantities observed in total cavopulmonary connection (TCPC) for the above conditions suggest that there are considerable differences in average (about 25-40%) and peak (about 50%) WSS distributions, when the non-Newtonian behaviour of the blood is taken into account. The lower WSS levels observed for non-Newtonian cases point to the higher risk of lesion formation, especially at higher pulsation frequencies. A realistic pulse form is relatively safer than a sinusoidal pulse as it has more energy distributed in the higher harmonics, which results in higher average WSS values. The present study highlights the importance of including non-Newtonian shear thinning behaviour for modelling blood flow in the vicinity of repaired arterial connections.

Red blood cell (RBC) aggregation and its influence on non-Newtonian nature of blood in microvasculature

“…The fluid dynamics model used here has been widely and thoroughly tested for both Newtonian and nonNewtonian blood flows in the past [30,31,46]. This flow model has been extended in the present study for the simulation of RBC aggregation and estimation of haemorheological changes in the microcirculation.…”

“…In the present model, dynamics of the blood plasma is obtained by solving the incompressible Navier-stokes equations and assuming that the flow is Newtonian [30][31][32]. The RBC's in the blood, represented using elliptical shapes, are suspended in the plasma in a two-dimensional computational domain.…”

“…The influence of RBC aggregation on the surrounding flow field, is introduced into the flow model through an aggregation parameter. To determine the influence of RBC aggregation on the flow nature, a powerlaw model has been incorporated into the flow model for the computation of shear dependent viscosity, which is suitable for low shear flows [29,30]. The following subsections provide a brief description of various components of the model employed.…”

“…The first objective is to improve the existing models for predicting RBC aggregation using a comprehensive framework that uses both drag and lift forces of the particles and different time scales. Such a comprehensive model is then applied to predict the non-Newtonian nature of the blood flow using a powerlaw model as the basis, which is valid for low Reynolds number flows [29,30].…”

Treatment planning for a TCPC test case: A numerical investigation under rigid and moving wall assumptions

“…Finally, the blood rheology was assumed Newtonian, as done in most of the computational modeling work on Fontan patients. However, it has been reported in that the shear thinning effects of blood affect the prediction of wall shear stress. Therefore, future studies assessing the effects of wall motion on wall shear stress in TCPC anatomies should assume a non‐Newtonian rheology.…”