## 4 Discussion
### Effect of the Aneurysm Size Modification
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{**Size Variation**} & \multicolumn{2}{c}{**Area-Averaged WSS Difference [\%]**} \\ \cline{3-4}  & & **Diastole** & **Systole** \\ \hline \multirow{3}{*}{RG-2} & III & 57.5 & 49.8 \\  & II & 123.1 & 116.7 \\  & I & 275.9 & 261.1 \\ \hline \multirow{3}{*}{RG-3} & III & 62.7 & 60.4 \\  & II & 122.7 & 107.8 \\  & I & 237.7 & 205.2 \\ \hline \multirow{3}{*}{UG-2} & III & \(-\)35.7 & \(-\)37.2 \\  & II & \(-\)18.2 & \(-\)17.9 \\ \hline \multirow{3}{*}{UG-3} & III & \(-\)4.6 & \(-\)0.4 \\  & II & \(-\)31.4 & 19.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Percentage variation in the WSS at the aneurysm dome with respect to the original size. Figure 20: Blood flow at the aneurysm region for geometries (**a**) RG-1 and (**b**) UG-1. As can be seen in Table 6, the maximum reduction in displacement for both ruptured geometries was achieved for the size II variation. For RG-2, this reduction was almost 30%, whereas for RG-3, the displacement was reduced at both diastole and systole by about 54%. UG-2 had the maximum displacement increment of about 60% for its largest variation. For UG3, the size II variation showed an increase in displacement of approximately 10%, while its size III variation showed a reduction of about 22% with respect to the original size. The evolution of von Mises stress with respect to the aneurysm size increment indicated that the larger aneurysms had a higher rupture risk. The percentage differences are presented in Table 7. For both ruptured geometries, the greatest reduction was achieved for size II variations, approximately 30% for RG-2 and between 23 and 29% for RG-3. For unruptured geometries, in both cases, the increase in the von Mises stress at the aneurysm was between 25 and 29%. Figures 16 and 17 show examples of the von Mises stress during aneurysm evolution for RG-3 and UG-3. It can be noted that the tops of the aneurysms showed higher levels of stress than other zones (except for the neck), even in the latter case, which had a smooth surface. This is in accordance with the zones where ruptures are typically found. For the ruptured geometries, a reduction in stress from size I to size II was observed, followed by an increment. This difference in behavior can be explained by the very different morphologies of the size I variations of the ruptured geometries. In both cases, these were semi-spherical aneurysms, and the change in curvature at their necks led to stress concentrations. Since these aneurysms were smaller than the rest of the cases, this had a greater impact on the average results. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{**Size Variation**} & \multicolumn{2}{c}{**Average Displacement Difference [\%]**} \\ \cline{3-4}  & & **Diastole** & **Systole** \\ \hline \multirow{3}{*}{RG-2} & III & \(-21.1\) & \(-17.9\) \\  & II & \(-29.3\) & \(-21.4\) \\  & I & \(-19.0\) & \(-11.1\) \\ \hline \multirow{3}{*}{RG-3} & III & \(-37.1\) & \(-38.6\) \\  & II & \(-54.6\) & \(-53.6\) \\  & I & \(-51.3\) & \(-48.5\) \\ \hline \multirow{3}{*}{UG-2} & III & \(57.1\) & \(60.0\) \\  & II & \(23.8\) & \(26.7\) \\ \hline \multirow{3}{*}{UG-3} & III & \(-21.3\) & \(-22.8\) \\  & II & \(9.6\) & \(9.6\) \\ \hline \end{tabular}
\end{table} 
Table 6: Percentage variation in the average displacement at the aneurysm dome with respect to the original size. Figure 21: Blood flow at the aneurysm region for UG-3 for sizes (**a**) I, (**b**) II, and (**c**) III.