Biomedical Engineering Reference
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Fig. 8.21
Structure mesh results of idealized (
a
) and image-based (
b
) models
USA). The blood flow distribution in the bifurcation adopts the method by Boutsia-
nis et al. (2004), where 71 % is directed through LAD and 29 % through LCx, and
this is unchanged through the entire cardiac cycle. Pulsatile aortic pressure was ap-
plied as an inlet boundary condition at the entrance of the main stem, and pulsatile
velocity conditions were imposed on both the LAD and the LCx outlet boundaries
(Fig.
8.22b
). As this study focuses on the local haemodynamic changes under dif-
ferent branch angulations, global coronary wall motion due to its attachment to the
moving myocardium is neglected to isolate the effects of wall compliance (Malve
et al. 2012; Torii et al. 2009a).
The blood was assumed Newtonian since the shear rate is large enough in coro-
nary arteries (larger than 100 s
−1
) to maintain a flow regime with nearly constant
viscosity (Gijsen et al. 2007; Joshi et al. 2004). The density and viscosity of the
blood are 1060 kg/m
3
and 0.0035 Pa-s (Chaichana T et al. 2012) respectively. The
blood was treated as laminar and a no-slip condition was applied at the arterial
walls. To eliminate local fluid dynamic effects on the reconstructed fluid domain
and ensure fully developed outlet flow conditions, a 10-diameter length inlet exten-
sion and 15-diameter length outlet extensions were added (Joshi et al. 2004).
The fully coupled FSI models were solved in commercial software packages
ANSYS CFX and ANSYS Mechanical (ANSYS Inc., Canonsburg, USA). FSI
models are coupled and solved iteratively by these two packages within each time
step by applying appropriate kinematic and dynamic conditions at the fluid-struc-
ture interface until the coupling system residual is less than a specified tolerance.
For each model, transient flow simulations over three cardiac cycles were per-
formed, and results at the last cycle were used for mechanical and haemodynamic
analysis.
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