Flow and stress characteristics in rigid walled and compliant carotid artery bifurcation models

Abstract

Computer simulation of pulsatile non-Newtonian blood flow has been carried out in different human carotid artery bifurcation models. In the first part of the investigation, two rigid walled models are analysed, differing in the bifurcation angle (wide angle and acute angle bifurcation) and in the shape of both the sinus (narrow and larger sinus width) and the bifurcation region (small and larger rounding of the flow divider), in order to contribute to the study of the geometric factor in atherosclerosis. The results show a significant difference in the wall shear stress and in the flow separation. Flow recirculation in the sinus is much more pronounced in the acute angle carotid. An important factor in flow separation is the sinus width. In the second part of the study, flow velocity and wall shear stress distribution have been analysed in a compliant carotid artery bifurcation model. In the mathematical model, the non-Newtonian flow field and the idealized elastic wall displacement are coupled and calculated iteratively at each time step. Maximum displacement of approximately 6% of the diastolic vessel diameter occurs at the side wall of the bifurcation region. The investigation demonstrates that the wall distensibility alters the flow field and the wall shear stress during the systolic phase. Comparison with corresponding rigid wall results shows that flow separation and wall shear stress are reduced in the distensible wall model.

Geometric multiscale modeling of the cardiovascular system, between theory and practice

“…In such districts, blood is modeled by means of the Navier-Stokes (NS) equations for incompressible homogeneous Newtonian fluids [64,149,184,185]. Effects related to non-Newtonian rheology such as the ones induced by pathologies (for instance the sickle cell disease) or in the capillaries need to be specifically addressed and are not considered in the present work.…”

Inexact accurate partitioned algorithms for fluid–structure interaction problems with finite elasticity in haemodynamics

“…This means that the physical interface conditions does not need in fact to be satisfied at each approximate-Newton iteration. In particular, the tolerance of the internal loop is taken proportional to the external residual (44) where suitable norms are used in each term of (44). The first term is the residual of the geometrical interface condition, the second one is the residual related to the fluid non-linearity and the third one is the residual related to the structure non-linearity.…”

“…This leads to the solution of a fluid-structure interaction (FSI) problem in three-dimensional (3D) real geometries [44,7,18,47,15,3,20,21]. To capture the complex dynamics characterizing such a problem, non-linear fluid and structure models have to be taken into account, leading to a complex non-linear coupled problem, formed also by the fluid domain subproblem when the fluid equations are written in Arbitrary Lagrangian-Eulerian (ALE) formulation [29,14].…”

Partitioned Algorithms for Fluid-Structure Interaction Problems in Haemodynamics

“…The fluid-structure interaction (FSI) problem in large vessels haemodynamics is characterized by a considerable amount of energy exchanged between blood and arterial wall in each cardiac beat [36,6,13,39,12,2,14]. This makes its numerical simulation particularly challenging.…”