Biomedical Engineering Reference
In-Depth Information
Fig. 5.39
Numerical study on the deformation of vessel wall and its associated blood flow struc-
ture using the FSI algorithm. In the default configuration, which is mainly used to as a reference to
compare with other cases, the vessel radius
r
= 0.005 cm, vessel length
L
= 0.06 m, vessel thickness
h
s
= 0.001 m, solid density
ρ
s
= 1000 kg m
3
, Young's modulus
E
= 750,000 Pa, Poisson ratio
υ
= 0.5,
fluid density
ρ
f
= 1000 kg m
3
and fluid dynamic viscosity
μ
f
= 0.01 Pa · s. At initial condition, fluid is
set to be at rest and pressure pulse with peak of 2000 Pa is imposed at the inlet
cardiac structure and blood in two separate modeling platforms, a physiologi-
cally realistic simulation can be outputted.
Fluid structure interaction for large cardiac wall deformation presents a difficult
problem. The fluid structure interaction must satisfy three important conditions: (1)
The structural solver describes nonlinear, anistropic and inhomogeneous cardiovas-
cular tissue characteristics; (2) The CFD code resolves large deformations on the
flow domains and updates the mesh accordingly; and (3) coupling of the fluid and
structural solver is needed to achieve convergence. For the fluid modeling, a finite
volume method can be used to discretize the Navier-Stokes equations, and for the
structural modeling, the nonlinear finite element method can be implemented.
As an example of vessel wall deformation such as the type is shown in Fig.
5.39
.
The combination of CFD with FEM is used to investigate the dynamic interaction of
blood flow with the vessel wall solid structure due to the a pressure wave propaga-
tion. The FSI simulations pertain to either a stable or oscillatory structural interac-
tion with its flow. One example would be the oscillatory deformation of heart valves
whereby the induced structural strain causes the valve to assume a state of reduced
strain, and before returning to its former state repetitively.
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