Applications of FSI for Cardiovascular Haemodynamics - Computational Hemodynamics: Theory, Modelling and Applications - page 245

pattern becomes non-symmetrical when increasing the degree of stenosis, and also
the minimum maximum principal stress becomes more negative.

8.2.4 Comparison Between FSI and Non-FSI Models

The study by Valencia and Villanueva (2006) is examined here which looked at the
unsteady non-Newtonian blood flow and mass transfer in symmetric and non-sym-
metric stenosis arteries (Fig. 8.10 ). This was compared for rigid and elastic models.
The compliant arterial wall uses the Mooney-Rivlin model. It is shown that by using
FSI, the arteries undergo significant dilation and compression due to the stenosis.
Figure 8.11 presents wall displacement and wall shear stress for symmetrical
and non-symmetrical stenotic artery due to 70 % occlusion and at systolic phase of
0.932 s. The maximum and minimum artery diameters at the inlet were at 3.4 mm
and 2.3 mm at systole and diastole respectively. The maximal effective stress at sys-
tolic time is around 0.25 MPa. However, at the stenotic throat, the effective stress is
about one order of magnitude smaller at approximately 0.05 MPa.
Valencia and Villanueva (2006) also evaluated the instantaneous recirculation
lengths at systolic time for the rigid and elastic wall arteries, and compared the
symmetrical and non-symmetrical stenosis for each. Based on different degrees of
stenosis, their comparison is shown in Table 8.2 . For the velocity inlet condition, the
recirculation length after the stenosis shows a positive correlation with the degree of
stenosis, while for the pressure inlet condition, this correlation becomes negative.
For a stenosis with 80 % occlusion, the flow does not show any recirculation zone
based on the pressure inlet boundary condition.
The study presented demonstrates that the degree of the stenosis influences its
recirculation length, wall displacement, and effective wall stress. Furthermore using
rigid walls produced less dilation and compression during the cardiac cycle in com-

Fig. 8.10 Geometrical models of stenosed arteries. Arterial channels based on ( a ) symmetric ste-
nosis and rigid wall; ( b ) non-symmetric stenosis with elastic wall; and ( c ) symmetric stenosis
artery with elastic wall. (Image from Valencia and Villanueva 2006)