Intra-aneurysmal pulsatile flow hemodynamics in low-aspect ratio Abdominal Aortic Aneurysms (AAA)*

Abdominal aortic aneurysm (AAA) is a pathological condition associated with irreversible dilation of aortic wall. Transient blood flow, originating at the heart heart [VG1] in the vicinity of a dilation generates abnormal flow hemodynamics that contributes to further wall weakening and sudden arterial ruptures. The present study numerically explores the pulsatile flow characteristics (Re_peak = 700 – 2200; f = 1.2 – 2.4 Hz) within low aspect ratio aneurysms (L/d = 1.5). Results reveal that for Re_peak = 700 - 1200, the aneurysmal flow is analogous to vortex mode i.e. vortex detaches from the free shear layer at the proximal wall and travels downstream towards the distal end. However, at Re_peak = 1200 – 2200, cavity mode is manifested i.e. the free shear layers remain confined within the proximal and distal limits and subsequently drive the primary vortex, that in turn stimulate the secondary and tertiary vortices. Furthermore, wall loading owing to spatio-temporal evolution of vortex structures is addressed through signatures of wall shear stress (WSS) and oscillatory shear index (OSI), respectively. Additionally, proper orthogonal decomposition (POD) is employed to exploit the energetic modes of vortex structures responsible for disease progression in the biomedical context.