Fundamentals of Haemodynamics - Computational Hemodynamics: Theory, Modelling and Applications - page 87

which relates pressure drop with flow velocity and geometry. The flow through the
ICA is more than twice the amount through the ECA branch, producing a greater
pressure difference to drive this flow. The flow patterns in Fig. 4.17b and c show the
main blood flow concentrating at the inner wall regions rather than the outer wall of
the bifurcation due to the vessel curvature. The presence of high velocity gradients
within the inner wall region of the ICA causes a high shear field along the inner wall
from the bifurcation apex to the carotid sinus. In addition, the abrupt cross-sectional
area expansion at the vicinity of carotid sinus causes flow separation along with a
pair of spiral secondary recirculating vortices located symmetrically about the me-
dian plane of the bifurcation (plane B-B).

4.7.2 Carotid Artery Bifurcation with Stenosis

To replicate the presence of a severe plaque, the healthy carotid artery used in the
previous section is modified to include a stenosis in the ICA by reducing the artery
sinus diameter just after the bifurcation apex (Fig. 4.16b ). Further details of this ex-
ample can be found in Dong et al. (2013). The stenosis reduces the cross-sectional
area by 63 % from the ICA branch entrance (plane A-A), to the throat of the stenosis
(plane B-B). To examine the plaque build-up influence on intravascular haemody-
namics, a steady numerical simulation is performed over the stenosed model while
keeping the boundary conditions identical with the previous healthy model.
The stenosis increases the flow resistance of the ICA branch, which requires a
greater pressure difference needed to conduct the blood flow through this branch—
which is more than twice the requirement for the healthy model (Fig. 4.18a ). A
characteristic jet flow is evident as the blood squeezes through the narrowed cross-
section. A negative pressure gradient dP / dy < is found leading into the stenosis 0

Fig. 4.18 CFD simulation results of the stenosed carotid bifurcation model