Wall Shear Stress Estimation of Thoracic Aortic Aneurysm Using Computational Fluid Dynamics

An attempt has been made to evaluate the efects of wall shear stress (WSS) on thoracic aortic aneurysm (TAA) using Computational Fluid Dynamics (CFD). Aneurysm is an excessive localized swelling of the arterial wall due to many physiological factors and it may rupture causing shock or sudden death. Te existing imaging modalities such as MRI and CT assist in the visualization of anomalies in internal organs. However, the expected dynamic behaviour of arterial bulge under stressed condition can only be efectively evaluated through mathematical modelling. In this work, a 3D aneurysm model is reconstructed from the CT scan slices and eventually the model is imported to Star CCM+ (Siemens, USA) for intensive CFD analysis. Te domain is discretized using polyhedral mesh with prism layers to capture the weakening boundary more accurately. When there is fow reversal in TAA as seen in the velocity vector plot, there is a chance of cell damage causing clots. Tis is because of the shear created in the system due to the fow pattern. It is observed from the proposed mathematical modelling that the deteriorating WSS is an indicator for possible rupture and its value oscillates over a cardiac cycle as well as over diferent stress conditions. In this model, the vortex formation pattern and fow reversals are also captured. Te non-Newtonian model, including a pulsatile fow instead of a steady average fow, does not overpredict the WSS (15.29 Pa compared to 16 Pa for the Newtonian model). Although in a cycle the fow behaviour is laminar-turbulent-laminar (LTL), utilizing the non-Newtonian model along with LTL model also overpredicted the WSS with a value of 20.1 Pa. Te numerical study presented here provides good insight of TAA using a systematic approach to numerical modelling and analysis.