Biomedical Engineering Reference
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Fig. 7.4  Physiological waveforms used in simulation. This fluid mechanical property, which is
based on flow rate, Q (ml/s), serves as the inlet boundary condition for the carotid artery used in
CFD simulation
incorporated at both inlet and outlets of the computational model. Vessel walls were
treated as rigid, and this will not affect physiological accuracy significantly because
previous research has shown that the effect of blood wave propagation on vessel
compliance can be generally regarded as secondary (Yiemeng Hoi et al. 2010). The
outlet pressure was set at 20 mmHg, which represents the capillary pressure, and the
SST model was applied in the simulation.
The generated mesh files were imported into a CFD package—ANSYS-CFX. In
this case study, 3D unsteady incompressible Navier-Stokes equations were solved
by a Second Order Backward Euler method. The convergence criterion for the
relative residual of all dependent variables was set to 1 × 10 −4 to ensure the con-
vergence of each time step, which is fixed at 0.004 s. To minimize the influence of
initial flow conditions due to the zero-velocity initial settings, all simulations were
carried out for four cardiac cycles based on a time period T of 4.0 s, and the results
presented were extracted from the third cycle onwards. Having a parabolic inlet
flow setting according to the Hagen-Poiseuille's law eliminates the need to add
an extra fluid domain to generate a fully developed flow at the inlet of the carotid
artery, which can reduce computational mesh element and expenses.
7.2.4
Experimental Validation
The overall methodology of an experimental validation study is depicted by Fig. 7.5 .
Validation is performed by comparing the haemodynamic parameters between the
numerical predictions and experimental measurements. The experimental measure-
ments provides a means for validation of the numerical simulated results and as
a form of support for fluid mechanists to review the accuracy of their simulation
platform. In addition, experimental data can be used to determine the boundary
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