Experimental unsteady flow study in a patient-specific abdominal aortic aneurysm model

The velocity field in a patient-specific abdominal aneurysm model including the aorto–iliac bifurcation was measured by 2D PIV. Phase-averaged velocities obtained in 14 planes reveal details of the flow evolution during a cycle. The aneurysm expanding asymmetrically toward the anterior side of the aorta causes the generation of a vortex at its entrance, covering the entire aneurysm bulge progressively before flow peak. The fluid entering the aneurysm impinges on the left side of its distal end, following the axis of the upstream aorta segment, causing an increased flow rate in the left (compared to the right) common iliac artery. High shear stresses appear at the aneurysm inlet and outlet as well as along the posterior wall, varying proportionally to the flow rate. At the same regions, elevated flow disturbances are observed, being intensified at flow peak and during the deceleration phase. Low shear stresses are present in the recirculation region, being two orders of magnitude smaller than the previous ones. At flow peak and during the deceleration phase, a clockwise swirling motion (viewed from the inlet) is present in the aneurysm due to the out of plane curvature of the aorta.