## 3 Results
### Impacts of the Stents on the Velocity Field and on Intra-Aneurysmal Flow  
The velocity field was visualized using three-dimensional streamlines that depict the behavior of the blood flow within the sac at systole and diastole. As expected, stenting leads to considerable hemodynamic changes within the considered vessel configurations during both phases. The resulting flow structures are sketched in Figures 2 and 3 for systole and diastole respectively. At systole, these are qualitatively similar for the different stent models, while a marked difference can be seen between the non-stented and stented cases for each respective configuration. In particular, all implants are capable of reducing the flow into the aneurysm. Additionally, it is apparent that the stent treatment is more effective for the S-shaped configuration in Figure 2. At diastole, the flow structures are again similar within the stented arteries. The three stents are effective, independent of the geometrical configurations of the artery. Of course their mission during diastole is facilitated by the reduced flow conditions. The more effective device here is STENT 2; the flow structure of STENT 1 looks similar to those of the unstented model. The behavior of STENT 3 is better than STENT 1 but slightly worse than that of STENT 2. There is a reduced tendency of the blood flow to circulate inside the aneurys sac. It is clear that, in these conditions, the stent with low porosity is the most efficient.  
Figure 2: Streamlines introduced at the inlet of each model, colored with the local velocity magnitude, plotted at the peak flow during systole for the same vascular geometry and for the three flow diverter stents considered in this study: (**a**) no stent, (**b**) STENT 1, (**c**) STENT 2 and (**d**) STENT 3.  
In Figure 4 the different flow rates entering the aneurysm are summarized using bar graphs. In a close-up view, the performance of each stent is shown separately. Surprisingly, for each artery geometry, the most efficient flow reduction is provided by a different device. In particular, for the V-bent configuration, the highest flow reduction is given by STENT 1, for the C-bent configuration by STENT 3 and for the S-bent configuration by STENT 2. It is likely that the geometries of the artery change the initial undeformed straight configuration of the stent. Due to the curvature of the vessel in fact, the stent mesh could locally slightly enlarge and slightly close near the neck, between the artery and aneurysm. This could explain why the low porosity stent is not the one that offers the highest flow reduction in all cases. This is especially true in the V-bent configuration. [PERSON] et al. [13] have highlighted similar findings. They report that when the curvature of the artery increases, the blockage effect of the stent diminishes and the flow into the aneurysm increases. In this sense, the high-porosity STENT 1 provides very similar performance for the different vessel configurations and seems to be less affected by geometry.  
Figure 4: _Cont._  
Figure 3: Streamlines introduced at the inlet of each model, colored with the local velocity magnitude, plotted at diastole for the same vascular geometry and for the three flow diverter stents considered in this study: (**a**) no stent, (**b**) STENT 1, (**c**) STENT 2 and (**d**) STENT 3.  
Finally, it is important to remark that, as stated in the literature, the degree of flow reduction and redistribution within the aneurys sac also depends on the orientation of the stent struts [45]. The orientation can be especially important for STENT 1, which has the thicker struts.