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Recent advancements in medical imaging techniques have enabled the accurate identification of unruptured intracranial aneurysms. To facilitate a proper patient management strategy, it is important to develop suitable mathematical models for their rupture prediction. To this end, the development of high-fidelity computational fluid dynamics (CFD) simulations with patient-specific boundary conditions will be useful in providing reliable hemodynamic parameters. In recent review articles, researchers have pointed out that, among several clinical and image-based indicators, morphological parameters, such as aspect ratio (AR) and size ratio (SR) of the aneurysm, correlated consistently with the rupture mechanism. However, it is not clear how these morphological indicators influence the hemodynamics-based CFD predictions. In the present work, the effect of these top-ranked morphological parameters on aneurysm hemodynamics and rupture prediction is investigated. Three patient-specific models have been used for analysis with the patient-specific inlet boundary conditions. We found that with an increase in AR and SR, the maximum value of wall shear stress (WSS) near the aneurysm neck is increased. Oscillatory shear index and relative residence time values are also increased with an increase in AR and SR. Furthermore, it was observed that an aneurysm with a multilobed structure shows complex flow, low WSS, and higher residence time over the secondary lobe. The turbulent kinetic energy and vorticity near the aneurysm neck are also increased with an increase in AR and SR.

Background and objectives Hemodynamics plays a crucial role in the progression of atherosclerosis and the treatment of arterial diseases. Stroke is one of the arterial diseases and a leading cause of death worldwide. Hemodynamics in the carotid artery plays a vital role in the stroke. The common carotid artery bifurcates into the internal carotid artery and the external carotid artery. Carotid sinus, a slightly dilated area, exists in the internal carotid artery just after the bifurcation and acts as a pressure receptor and regulator. The location and size of the sinus can vary in different people; the change in sinus size and location may affect the hemodynamics. It is necessary to study the shift in hemodynamics due to changes in sinus size and position on atherosclerosis. The change in flow behavior may suggest the probable sites of backflow and low wall shear stress, and therefore the sites prone to atherosclerosis. Methods The model of the carotid artery has been constructed using patient data. Transient computational fluid dynamics simulations have been performed using a finite volume method for the numerical solution in a three-dimensional computational domain using ANSYS Fluent 19.2. Pulsatile flow is specified at the inlet boundary. The coupled scheme is used for the pressure-velocity coupling. The second-order discretization scheme is used for pressure interpolation and second-order upwind scheme is used for the discretisation of momentum equation. The temporal term is discretized using the first-order implicit scheme. Results The effect of sinus size and location on the overall flow behavior, wall shear stress, and secondary flow are presented. Results show that the outer wall of bifurcation has low wall shear stress and bigger recirculation as compared with that on the inner wall of bifurcation. Numerical results obtained for varying sinus size and position are shown in graphs and contours, including wall shear stress, secondary flow, and velocity streamlines. Conclusion Numerical results reveal that sinus away from bifurcation, and larger diameter sinus has more recirculation and low wall shear stress. Therefore, the person having sinus away from bifurcation and larger sinus diameter are more susceptible to plaque formation.

Flow behavior at the arterial bifurcations has significant implications on the plaque formation. It depends on the vessel size, two bifurcation angles, i.e. angle between the mother and daughter vessels and their relative magnitudes. In this study, hemodynamics for steady and pulsatile flow of blood has been investigated in an idealized carotid artery bifurcation having all the vessels in the same plane for a range of bifurcation angles for symmetric and asymmetric bifurcation. The simulations reveal the presence of a pair of helical vortices, symmetric about the bifurcation plane, in each daughter tube near the bifurcation.

Bifurcating vessel is a characteristic feature of biological systems such as arteries in the cardiovascular system and pulmonary airways. In cardiovascular system, the bifurcations are often asymmetric, flow is pulsatile, and the fluid, blood, shows a complex rheology. In this work, we study computationally pulsatile flow in planar symmetric and asymmetric, three-dimensional bifurcating vessels. The fluid is considered to be Newtonian as well as non-Newtonian following Carreau's model, and the results are compared. While the flow divides in the two daughter tubes equally in symmetric bifurcations, the flow distribution is time-dependent during a cardiac cycle in asymmetric bifurcations. The flow pattern changes significantly during a cardiac cycle. The secondary flow caused by a turning streamline is analyzed in terms of secondary velocity, vorticity, and helicity. Significant variation is observed in the secondary flow in a cardiac cycle. The secondary flow is observed to be stronger at the start of the diastole despite reduced flow rate. The separated flow on the outer wall causes a significant reduction in time-averaged wall shear stress, a biomarker to assess the possibility of atherosclerotic plaque development. While no significant difference is observed in the results obtained for Newtonian and non-Newtonian fluids at high shear rates, for example, during systole, significant differences are observed when the shear rate is low, during diastole or in the separation region. The velocity profile for the non-Newtonian fluid is observed to be flatter than that for Newtonian fluid. Further oscillatory shearing index, relative residence time, the parameters used as biomarkers are presented.