Experimental investigation of physiological flow in abdominal aortic aneurysm

In this study, it is aimed to understand the effect of flow patterns with varying Reynolds and Womersley numbers on the basic flow characteristics of the flow field in the model of the abdominal aortic aneurysm. Three types of flow conditions, namely, steady, sinusoidal, and physiological were investigated experimentally by using the particle image velocimetry (PIV) method. Time-averaged experiments were carried out at 〖Re〗_mean=178, 431, 860, and 1151 for Womersley numbers ∝=3.68 and 6.72. Three Reynolds numbers 〖Re〗_mean=178, 431, and 860 were chosen to achieve phase-averaged experiments, with two different Womersley numbers ∝=3.68 and 6.72. The general characteristics of the flow structure of cases investigated by time-averaging were found as flow separation at the proximal end of the model, and reattachment at its distal end. Two counter-rotating vorticity concentrations occupied the entire circular bulge with their centers located closer to the distal end of dilatation. The most two noticeable effects of increasing Reynolds numbers were the displacement of the center of vortices near the distal end of the model and the augmentation of vorticity contours' peak value. The evolution of vortices within the abdominal aortic aneurysm (AAA) was observed to be dependent on flow patterns. Under pulsatile flow conditions, a vortical flow structure started to form near the proximal and displaced closed to the distal end during the cycle and vanished at the end of the period. However, under steady flow conditions, the size and center of the vortical flow structure were stable. Sinusoidal and physiological flow conditions revealed different vortical flow structures and peak vorticity levels.