## 3 Results
### Biomechanical Behaviour of Healthy and Diseased Aortas
#### 3.4.1 Healthy Aorta  
The first work from the selected database reporting numerical modelling in healthy aortas was in 2006 by [PERSON] et al. [72]. In this work, CFD simulations considering a non-Newtonian fluid were performed on idealised geometries. The aim was to elucidate how numerical tools can be used to recreate the haemodynamics on the aortic arch. Their findings on the axial flow profiles revealed complex temporal variances and skewness towards the inner curvature of the arch. They also postulated that vascular geometry (e.g., branching, non-planar, curvature, asymmetry), as it highly influences local fluid dynamics, could be the primary cause in the development of atherosclerosis. Later, in 2011, [PERSON] et al. [73] reported the development of FSI simulations on Magnetic Resonance Imaging (MRI)-driven geometric models. Patient-specific velocity profiles were used as an inlet BC and the external pressure exerted by surrounding vessels (e.g., pulmonary trunk and superior vena cava) was modelled as a linear elastic support BC on the outer wall. The model proved to be able to reproduce physiologically admissible flow patterns that presented close agreement with MRI data for lower-velocity regimes. [PERSON] et al. [74] also resorted to FSI simulations specifically to model the leaflet motion of the Aortic Valve (AV). The left ventricle and the aorta were modelled as rigid cylindrical tubes and the blood was considered slightly compressible to improve numerical convergence. The results evidenced that higher stresses appeared on collagen fibres and that Bicuspid Aortic Valve (BAV) induced flow turbulence and led to higher velocities and WSS magnitudes. [PERSON] et al. [75] also used FSI formulations to simulate the blood flow on the Sinotubular Junction (STI). A rigid model of the aorta and valve leaflets (peak systolic configuration) coupled with a contractile left ventricle mimicked the blood ejection into the aorta. Among their findings was the evidence of turbulence created at the left ventricle that travelled towards the aorta and higher WSS were found in the aorta. [PERSON] et al. [76] performed patient-specific CFD simulations using FVM to calculate the haemodynamics of the aortic arch. Larger velocities near the inner wall and the presence of clockwise helical flow and recirculation zones was evidenced. [PERSON] and [PERSON] [53] also performed FSI simulations on AV virtualisations, but in this particular case, the blood flow was modelled with a ROM (1D). A good agreement was found with regular FSI simulations and showed that increased bending stiffness reduces the opening area and considerably increases flow resistance. On the other hand, excessively low values of bending stiffness are also not desirable as the leaflets may present flapping oscillation. [PERSON] et al. [77] performed CFD analysis on patient-specific models of the abdominal aorta and its branches. The geometries were reconstructed via CT data segmentation and comprised a total of 16 outlets. The authors postulated that the flow was almost entirely stable upstream of the abdominal aortic bifurcation. Downstream of the bifurcation, secondary blood flow with recirculation zones was formed. Moreover, WSS analysis revealed distributions with low, high and supra physiological magnitudes during the cardiac cycle and particles that presented long residence times near the wall, which is known to be a contributing factor to atherosclerosis.