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|Title: ||Investigation of blood cells migration in large stenosed artery|
|Authors: ||Shuib, Anis Suhaila|
|Supervisor(s): ||Easson, William|
|Issue Date: ||25-Jun-2012|
|Publisher: ||The University of Edinburgh|
|Abstract: ||Atherosclerosis is one of the main diseases responsible for the high global mortality rate
involving heart and blood vessel disorders. The build-up of fatty materials in the inner wall
of the human artery prevents sufficient oxygen and nutrients reaching the organs of the body.
Atherosclerosis is a chronic, long term condition, which develops and progresses over time;
however, the disease does not present any symptoms until an advanced stage is reached,
which results in potential permanent debility and sometimes sudden death.
This thesis is concerned with the progression of atherosclerosis in an artery with mild
stenosis that has resulted in a 30% reduction in its diameter. To this end, data on the low wall
shear stress has been correlated with the atherosclerotic prone region. In a stenosed artery,
this region corresponds to the separation zone that is formed distal to the lumen reduction.
Atherosclerosis is a complex phenomenon, and not only involves wall shear stress, but also
cellular interactions. Previous research has shown that even in the absence of wall biological
effects, the blood cell distribution is strongly influenced by the hydrodynamics of the fluid.
The mechanisms of blood cell distribution and the dynamic behaviour of the blood flow
were investigated by developing a physical model of the stenosed artery, and by using
particles to represent the presence of the blood cells. Particle Image Velocimetry system was
employed and the size of particles were the 10μm and 20μm.The flow field was
characterised and the particle distribution was measured.
The characteristics of steady flow in the stenosed artery at Reynolds numbers of 250 and 320
revealed the importance of fluid inertia and the shear gradient distal to stenosis. Unequal
distribution of the particles modelling the blood cells was observed, as more particles
occupied the recirculation zones than the high shear region and central jet. The particle
migration was found to depend on the particle size, particle concentration and fluid flow
rates. The results suggested that the presence of similar effects in the real human arterial
system may be significant to the progression of atherosclerotic plaques. At lower Reynolds
number of 130, a particle depleted layer was observed at the wall region. In physiological
flow the cell free layer will prevent the transport of oxygen and nitrogen oxide (NO) to the
A numerical method was used to simulate the flow characteristics measured in the
experiment. The numerical results revealed the importance of the hydrodynamic mechanism
of particle migration. Drag and lift forces were found to affect the residence time of particles
in the recirculation region.
The findings of this work have suggested that for a complex geometry like a large stenosed
artery at physiological flow rates, hydrodynamic forces are important in cell migration in the
flow separation zone. Even without biological forces, the cells migrate to the low wall shear
stress region. For computational dynamics studies, this study has demonstrated the need for
higher-order modelling at the cellular level in order to establish the particle migration
|Appears in Collections:||Engineering thesis and dissertation collection|
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