Biomedical Engineering Reference
In-Depth Information
behaviour. These studies can help to better understand the chaotic flow structure of
transition turbulence, which is significant in the plaque weakening mechanism.
7.2.5
Flow Visualisation
Path streamlines that act as massless particle tracers to track the flow path of the
blood, are released from the CCA inlet with a flow rate of 12.17 mL/s to provide
qualitative visualisation of the flow field. The flow characteristic inside the ste-
nosed carotid bifurcation is illustrated in Fig.
7.10
. The streamlines in the carotid
bifurcation at the stenosis, has a maximum velocity of approximately 0.28 m/s. In
this region there is flow separation and reversed flow just posterior to the narrowest
stenosis.
Contours of axial velocities are plotted on seven equally spaced slices normal to
the flow direction (numbered 1-7). As depicted in slice 1, a Womersley flow profile
with uniform streamlines is established at the upstream of the sinus region. After
passing through this region, the flow enters both the internal and external carotid
arteries (i.e. ICA and ECA). Velocity distributions are highly skewed toward the
outer vessel walls. Similar findings have also been reported, where skewed flow
structures are primarily caused by the misalignment of the mean axis of arteries (Ve-
tel et al. 2009). Further downstream, strong flow separation and secondary flows are
exemplified by streamlines. Owing to the rapid enlargement of the cross-sectional
area, flow separation firstly occurs at the sinus region (see streamlines between
slices 1-3). Similar flow separation is also found downstream of ICA as the flow
continues through the stenosis (see streamlines after slice 7a). Streamlines between
slices 4b-7b show a strong swirling secondary flow in the ECA. The inception of
such flow is due to the action of centrifugal forces caused by the curvature of lumen,
Fig. 7.10
Flow visualisa-
tion in a stenosed carotid
bifurcation. The contour
plots of axial velocities
and streamlines traces in a
stenosed carotid bifurca-
tion are presented after
extraction of the flow
information within the
anatomical geometry. This
flow visualisation allows
us to understand the flow
condition within a diseased
artery effectively
Search WWH ::
Custom Search