Abstract

An Abdominal Aortic Aneurysm (AAA) is a vascular disease affecting seniors. It is described by an inflation of the aorta in the abdominal regions. The specific reason for this disease is not clear.Rupture of AAAs leads to death and current surgical interventions are risky and require frequent follow-up AAAs are usually associated with an Intraluminal Thrombus, which prevents blood from conveying oxygen and nutrition to the AAA walls. Formation of thrombosis are strongly affected by hemodynamics, and especially blood stasis.

It has been founded that blood stasis can be triggered by a reduction of flow rate such as that during sleeping or in people who suffer from lower limb amputation.

This change has been evaluated experimentally by time-resolved Particle Image Velocimetry. A compliant AAA model that has an aortic arch, renal arterirs, and an iliac bifurcation was designed
and tested under normal and low flow conditions in terms of velocity behavior, residence time of particles inside the AAA, and shear history of particles during their movement.

Proper orthogonal decomposition and Dynamic mode decomposition have been applied to the flow in both planes to reveal the hidden dynamics and the coherent structures of the flow behavior inside the AAA.

The flow inside an AAA is mainly described by the jet penetrating the AAA with a large recirculation zone in the lumen. The velocity snapshots do not show a major difference between the two cases. Hidden dynamical structures were revealed by proper orthogonal decomposition and dynamic mode decomposition. Most of the small-scale dynamics occur near the entrance of the AAA. Vortical structures have been found to play a beneficial role in preventing thrombus formation. This study recommends focusing on the low flow conditions and developing a method that can promote blood flow mixing in patients with an AAA. The current study is the first study to evaluate the time-resolved behavior of the fluid flow inside AAAs and to decompose it into dynamical modes.