Computational Modeling and Simulation Examples in Bioengineering. Группа авторов
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Название: Computational Modeling and Simulation Examples in Bioengineering
Автор: Группа авторов
Издательство: John Wiley & Sons Limited
Жанр: Химия
isbn: 9781119563914
isbn:
Results
Results for two examples of the symmetric AAA are given here: (i) case with rigid walls and (ii) AAA with deformable walls. Results not shown here and solutions for other model parameters can be obtained using Software on the web.
Modeling of AAA Assuming Rigid Walls
We analyze an aneurism at the straight aorta domain, where aorta proximal and distal to the AAA bulge is idealized as straight rigid tube and branching arteries are excluded. The model has ratio D/d = 2.75 and geometry generated according to Figure 1.5 (D and d are diameters of the bulge and aorta, respectively). The data are: blood density is ρ = 1.05 g/cm3; kinematic viscosity (Newtonian fluid) ν = 0.035 cm2/s, d = 12.7 mm. The inflow velocity is defined by the flux function given in Figure 1.6. The FE mesh consisted of approximately 8000 3D 8‐node brick elements.
The results for the velocity and pressure at peak systole t/T = 0.16 are shown in Figure 1.7. The velocity disturbance in the region of the aneurism is notable. Also, the region of maximum pressure is located inside AAA.
Figure 1.7 Velocity field (left panel) and pressure distribution (right panel) for peak systole t/T = 0.16 of AAA for the model with D/d = 2/75, d = 12.7 mm.
Modeling AAA with Deformable Walls
Here, an aneurysm of the straight aorta with deformable walls is modeled according to the FSI algorithm. Blood flow is calculated using 2112 eight‐node 3D elements, and 264 four‐node shell elements used to model the aorta wall, with the wall thickness δ = 0.2 cm. The material constants for blood as in the previous example, while data for the vessel wall are: Young's modulus E = 2.7 MPa, Poisson's ratio v = 0.45, wall thickness δ = 0.2 cm, and tissue density ρ = 1.1 g/cm3. Boundary conditions for the model are prescribed velocity profile (see Figure 1.8a) and output pressure profile as given in Figure 1.8b.
Figure 1.8 Input velocity and output pressure profiles for the AAA on a straight vessel. Inlet peak systolic flow is at t = 0.305 s and outlet peak systolic pressure is at t = 0.4 s. (a) Velocity waveform; (b) pressure waveform.
Source: Modified from Scotti et al. [44].
The results for velocity magnitude distribution at t = 0.305 s are shown in Figure 1.9a. The von Mises wall stress distributions at t = 0.4 s is given in Figure 1.9b. It can be seen that the velocities are low in the domain of the aneurism, while the larger values of the wall stress are at the proximal and distal aneurism zones.
Figure 1.9 Velocity magnitude field and von Mises wall stress distribution for symmetric AAA on the straight vessel. (a) Velocity field distribution for peak at t = 0.305 s; (b) von Mises wall stress distributions for blood pressure peak at t = 0.4 s.
References
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