A numerical study on pulsatile non-Newtonian hemodynamics in double-fusiform abdominal aortic aneurysms

Abstract

Abdominal Aortic Aneurysm (AAA) is a multi-factorial pathological event that occurs in the human body. In the present work, the hemodynamics pertaining to AAA are numerically analyzed. To comprehend the blood flow phenomenon in a double-fusiform aneurysm, axisymmetric simulations of pulsatile non-Newtonian blood flow are performed using OpenFOAM. The Carreau–Yasuda model is used to evaluate the non-Newtonian behavior of blood. The Reynolds number and Womersley number are altered as per the physiologically applicable range to characterize the hemodynamics. The Dilatation Index is also varied to quantify the consequence of different enlargements of the abdominal aorta on the blood flow. Four hemodynamic indicators—time-averaged wall shear stress, Oscillatory Shear Index (OSI), Relative Residence Time (RRT), and vascular impedance—are used to identify several complications such as atherosclerosis, vascular inflammation, endothelial dysfunction, and hyperplasia. As the pulse rate increases, the chances of particle stagnation inside the aneurysm decrease due to lower RRT. Our results suggest that patients with hypoxia or bradycardia (low Womersley number) are more susceptible to atherosclerosis due to the high value of RRT. Thus, we recommend mild exercise for patients with AAA. After analyzing the hemodynamic indicators, % of area with RRT > 0.5 is identified as the critical parameter to propose a regime map. Low pulse rates are found to be critical at low flow rates, whereas high pulse rates are found to be critical with high flow rates. Furthermore, it is found that the severity increases as the size of the aneurysm increases.