The purpose of this paper is to conduct a numerical simulation of the stroke patient's cerebral arteries and investigate the flow parameters due to the presence of stenosis. The computational fluid dynamics (CFD) simulations are based on simplified and realistic cerebral artery models. The seven simplified models (benchmarks) include straight cylindrical vessels with idealized stenosis with variable d/D (0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1). The realistic model of the cerebral artery is based on magnetic resonance imaging (MRI) for patient-specific cerebral arteries. The simulation for the realistic model of the cerebral artery is performed at boundary conditions measured by ultrasonography of the input and the output flow profiles (velocity and pressure). The obtained CFD results of the benchmarks are validated with actual data from the literature. Furthermore, a previous vascular contraction is assumed to be exist and the effect of this contraction area ratio on the blood flow regime is discussed and highlighted. Furthermore, CFD results show that a certain vascular contraction area critically affects the blood flow which shows increasing the wall shear stress WSS at the stenosis site. An increase in the blood velocity and vortex appears after the contraction zone, this lead to vessel occlusion and strokes. Article highlights The pressure drop across the arterial contraction is reduced when the area ratio d/D is increased. In some cases, the vortex can prevent blood flow from crossing, this leads to vessel occlusion especially at low d/D The WSS near the contraction area is high. Increasing the WSS can cause embolism that leads to lead to vessel occlusion.

The numerical simulations of this paper present the flow structure of an isothermal cylinder with curved corners r/R = 0.5, where R is the half-width and r is the corner radius of the cylinder, with varied angle of attack, α (0° ≤ α ≤ 45°). The cylinder is located perpendicular to the air stream flow with Re = 180 and Pr = 0.7. The solution of the governing equations obtained using ANSYS-FLUENT package. The variation of α from 0° to 45°, leads to two major flow regimes A and B. The flow regime of type A appears at small range of α (0° ≤ α < 10°), can be termed as trailing corner separated flow. The flow regime of type B appears within the large range of α (10° ≤ α ≤ 45°), can be termed as leading-trailing corner separated flow. The flow structure is unsteady and characteristic by alternating Kármán vortices appears for each α. The maximum vorticity | |max is inversely linked to the wake bubble length . The lower core (positive) instantaneous vorticity increases with increasing α with slight increasing for α = 0° -5° and 30° -45°, while large increasing for α = 5° -30°.

In this study, we investigate the hemodynamics parameters and their impact on the aneurysm rupture. The simulations are performed on an ideal (benchmark) and realistic model for the intracranial aneurysm that appears at the anterior communicating artery. The realistic geometry was reconstructed from patient-specific cerebral arteries. The computational fluid dynamics simulations are utilized to investigate the hemodynamic parameters such as flow recirculation, wall shear stress, and wall pressure. The boundary conditions are measured from the patient using ultrasonography. The solution of the governing equations is obtained by using the ANSYS-FLUENT 19.2 package. The CFD results indicate that the flow recirculation appears in the aneurysms zone. The effect of the flow recirculation on the bulge hemodynamics wall parameters is discussed to identify the rupture zone.

The aim of this study is to investigate the fluid flow structure and heat transfer from an isothermal cylinder with a curved corner radius ratio (r/R) of 0.5, and attack angle (α) is varied between 0° ≤ α ≤ 45°. The cylinder is subjected to airflow at a Reynolds number (Re) = 180 and Prandtl number (Pr) = 0.7. This study focuses on the effect of α on the fluid forces, Strouhal number, Nusselt number, and flow structure, and wake bubble size. The sensitivity of the time-mean drag and lift forces is investigated to α, and they appear to be minimum at critical α of 5° and 12°, respectively. The increase of α from 0 to 45° results in about 12.9% enhancement in the heat transfer from the cylinder.