## 3 Results
### Biomechanical Behaviour of Healthy and Diseased Aortas
#### 3.4.2 Aortic Aneurysms  
Our database revealed that 12 works focused on studying the biomechanical behaviour of aortic aneurysms (e.g., ATAA, AAA, Descending Thoracic Aortic Aneurysm (DTAA) and saccular aneurysms). [PERSON] et al. [63] developed both CFD and CSM models based on the FEM technique, to study the haemodynamics and structure of patient-specific AAA. Their results highlighted the existence of recirculation zones and increased WSS, which was not found in healthy patients. Structurally, it was shown that patients with a known rupture appeared to have superior Peak Wall Stress (PWS). [PERSON] et al. [21] improved the methodology described in the previous work by developing a two-way FSI simulation, using partitioned schemes. [PERSON] et al. [62] also developed two-way FSI to assess the effects of dilatation and aspect ratio on the haemodynamics of idealised models of AAA. The numerical results showed the formation of two vortices, which were appointed as the dominant aspect of fluid dynamics. Moreover, elevated Oscillatory Shear Index (OSI), which is highly correlated with endothelial malfunctioning, was also found. [PERSON] et al. [67] performed CFD simulations in patient-specific geometries. The haemodynamics of saccular transverse aortic aneurysms was analysed. Higher WSS magnitudes and increased turbulence (vortices and recirculation) were found at the dilated region. [PERSON] et al. [39] explored the differences in haemodynamics and WS induced by BAV using a two-way FSI approach and structured meshes. Evidence of an intrinsic disturbed blood flow was found in BAV patients; this contributes to an asymmetric and elevated WSS distribution. The inner layer was subjected to significantly higher principal stress and a greater inner-outer wall pressure gradient was found on the STJ area, supporting the hypothesis that this region is the most susceptible to dissection. This was later also postulated by [PERSON] et al. [78], where CFD simulations highlighted that abnormal WSS distributions promote medial degeneration, which may be one of the main causes of AD development, and that the STJ presented with higher values of OSI and WSS. [PERSON] et al. [79] evaluated the influence of anatomical features on aortic haemodynamics. A two-phase mixture model to measure the evolution of red blood cells on the blood flow, Quemada non-Newtonian rheological model and four different groups (healthy, BAV, aneurysm and elongated transverse aorta) were considered to perform the CFD simulations. It was shown that anatomical variations had a great impact on flow patterns. On some occasions, recirculation zones, characterised by lowered blood cell concentrations and elevated WSS, were found, in which the non-Newtonian behaviour of blood significantly altered the results. [PERSON] et al. [66], following an approach similar to [PERSON] et al. [79], investigated the influence of several geometrical factors (thickness, maximum diameter, tortusity and asymmetry) on the WS distribution of ATAA. Several sets of idealised distinct geometries were generated to study each factor individually. They assessed that PWS increases with higher maximum diameter, asymmetry and tortusity and decreased thickness. [PERSON] et al. [80] performed patient-specific FSI simulations under normative and hypertensive conditions. The presented results implied that wall motion was highly influenced by blood pressure and local geometrical characteristics and that WS distribution was highly inter-patient heterogeneous. [PERSON] et al. [65] also developed a two-way coupled FSI model to study the influence of peripheral vascular resistance and wall mechanical properties on WS. Their findings suggested that aortic stiffening contributed to abnormal WS distributions and predisposed the aortic wall to rupture. The increase in peripheral resistance translated into elevated blood pressure, which makes the aortic wall more susceptible to rupture as well [80]. [PERSON] et al.