Biomedical Engineering Reference
In-Depth Information
FIGURE 13.8
The shear
stress history of platelets
within the left coronary
model estimated using the
Boussinesq approximation,
following their trajectories
for five cardiac cycles. The
two exported shear stress
histories are for the lowest
trace (gray particle) and the
highest
Light gray particle
Highest trace
2
1.5
1
0.5
0
0
0.9
1.8
2.7
3.6
4.5
Time (sec)
trace
(light gray
particle).
8
6
4
2
0
Gray particle
Lowest trace
X
0
0.9
1.8
2.7
3.6
4.5
Z
Time (sec)
Y
exported from the simulation along the trajectory for five cardiac cycles, calculated using
the Boussinesq approximation.
Using the approach discussed above, more information about the discrete phase in
blood can be gained; however, this is still very limited. To achieve more accurate informa-
tion on the discrete phase, such as cell deformational change, microparticle shedding, sur-
face protein expression, more complicated models and modeling techniques (including
kinetic reactions), as well as sufficient physiological knowledge are required. No commer-
cial software is available to conduct these types of simulations, and therefore, sophisti-
cated and elegant programming will be required by the research group interested in these
questions.
13.2 FLUID STRUCTURE INTERACTION MODELING
The necessity for fluid structure interaction modeling arises when a flexible structure
either has a fluid flowing through it or the flexible structure is immersed within a fluid.
One of the most common examples of fluid structure interaction modeling (FSI) is of blood
flow through the cardiovascular system. As we have learned in previous sections, blood
vessels are not rigid, and they distend in response to the heart's pressure pulse. Under car-
diovascular disease conditions such as aneurysm, the distensibility of blood vessels
increases, and the need for FSI modeling to more accurately describe these conditions is
increased. To accurately predict and understand the flow through these types of struc-
tures, the motion of the structure must be depicted. The mechanical properties of the
vessel must be known or assumptions must be made about these properties. There are a
number of different models that can be used to solve these problems, which include
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