The formation and growth of intracranial aneurysms are partly attributed to various hemodynamic factors, such as the wall shear stress and pressure. However, the exact nature of the hemodynamic variables responsible for triggering aneurismal growth is still unknown. The conclusions drawn by various studies in this regard are found to be speculative and sometimes ambiguous. This issue is further investigated in the present work using some new insight gained from passive scalar dispersion in the blood flow for realistic aneurysm geometries. Intracranial aneurysms are best visualized using selective catheter angiogram technique where a contrast agent added to the blood flow is visualized and filmed dynamically. In the current study, the 2D threshold images produced by “3D rotational X-ray angiography technique” are used in an “in-house” program to construct a 3D volumetric grid which is then used to calculate the blood flow through the aneurysm. The dispersion and flow patterns show the localization of high stress in stagnation areas resulting from secondary flows, which may be the potential regions for the origin and growth of aneurysms. The dependence of flow properties on the initial and boundary conditions to calculate the pressure and the wall shear stress values for a given geometry are investigated. A detailed grid dependence study is also performed to show the dependence of the wall shear stress calculations on the quality of near-wall grid resolution. An estimation of discretization error was made using the procedure recommended by ASME Journal of Fluids Engineering. The results suggest high dependence of calculated WSS on local grid density.

Finally, the aneurysms were virtually removed to identify the hemodynamic factors responsible for aneurysm formation. For these arterial flows without the aneurysm, the results suggest the occurrence of secondary flow impingement patterns and high oscillatory wall shear stress in the regions where the aneurysm was initially present. These factors, over the lifetime of the patient, might lead to the degradation of arterial wall leading to the formation of an aneurysm.