Experimental study on impact of inflow conditions on large-scale flow structures in an aneurysm

Aneurysms are abnormal ballooning of weakened blood vessels, and a ruptured aneurysm can be debilitating or fatal. Studies have shown that aneurysm formation, growth, and rupture are correlated to the interplay of different parameters such biomechanical, biophysical, and hemodynamics. Several studies have shown that aneurysm hemodynamics influence the behavior inside the aneurysm; however, its hemodynamics is not yet fully understood. This leads to inaccurate risk assessment and limited treatment options. This study focuses on investigating the hemodynamics inside an aneurysm for different inflow conditions and varying geometrical shapes. For this investigation, two idealized rigid sidewall aneurysm models were used with low and high risk of rupture. An in-house experimental setup was developed for this investigation where inflow conditions such as Womersley number (α) and Reynolds number (Re) can be precisely controlled. Re and α were varied between 50-250 and 2-5, respectively. A ViVitro Labs pump system was used to pump the fluid and Particle Image Velocimetry (PIV) was used to perform velocity measurements. The flow evolution, vortex path, impinging location, and vortex strength were determined using the velocity field data. The investigation showed that the primary vortex path was correlated to the increase in α, while the vortex strength and formation of secondary vortices was correlated to the increase in Re. The vortex evolution and decay of these large-scale structures were also found to be correlated to the change in Re and change in α. Furthermore, the results clearly showed that aneurysm morphology also played an important role in formation and movement of the primary and secondary vortices in the aneurysm.