Numerical Simulation for Blood Flow - Microsurgery: Advances, Simulations, and Applications - page 200

shows the Mises stress for the ICA model. The maximum Mises stress
occurs at the bifurcation and near the base of bifurcation at systole
phase. In addition, Fig. 5.25 also shows that the stress on the front
face is higher than that on the lateral face.

5.4.10 Discussion

Aneurysm initiation is believed to be caused by the interaction of
abnormally high-low hemodynamic forces and the arterial wall. 12,13
From Fig. 5.22, oscillated locally high wall shear stress more than
15 Pa at the bifurcation can cause the fragmentation of the internal
elastic of blood vessel and can be a trigger of aneurysm initiation.
Mises stress is also focused on the bifurcation. Therefore, stress on
a vessel wall also can be an index value of aneurysm initiation as the
same way of wall shear stress. A wall shear stress value lower than
4 Pa is reported to cause atherosclerotic change on the vessel wall
[10], and this low wall shear stress causes the degeneration of the
vessel, such as thinning and weakness of vessel wall, also vascular
narrowing by the aggregation of plaque. From the results shown in
Figs. 5.23(a-c), vortex lows in blood vessel invoke stagnation. As
shown in Fig. 5.22, the wall shear stress outside larger bifurcation
where vortex low exists is nearly equal to 0. Therefore, the region
of low wall shear stress can develop stenosis. As a future work, the
validation between numerical simulation and experimental results
needs to be conirmed. Furthermore, we apply FSI analysis for
complex cases, such as atherosclerosis and aneurysm models.

5.4.11 Conclusion

FSI analyses were carried out for one ICA model reconstructed
based on CT images. Moreover, we constructed the geometry data
of the vasculature model with thickness and its material elasticity,
such as Young's modulus and Poisson ratio is considered. The results
of wall shear stress and Mises stress show that oscillatory locally
high stress can cause aneurysm initiation and low wall shear stress
leads to atherosclerotic change on the vessel wall. From the result
of velocity magnitude after bifurcation, blood low speed of the
internal vessel is faster than that of the outer. At the diastole phase
( t = 0.50 s), vortex structure outside of vessel decreases the velocity
of blood low to nearly 0 m/s and stagnation of low. The streamline