Session: 07-02-01: Vibration and Acoustics in Biomedical Applications

Paper Number: 166536

Computational Analysis of Cerebral Aneurysm Flow Dynamics at M2 Bifurcations Using the Low-Reynolds k-ω Turbulence Model 

Middle cerebral artery (MCA) aneurysms account for approximately 14–43% of all cerebral aneurysms and pose a serious health risk due to their potential for rupture. The rupture of an intracranial aneurysm can result in subarachnoid hemorrhage and intracerebral hematoma, leading to severe neurological deficits, long-term disability, or death. Studies have shown that aneurysm rupture is associated with high mortality and morbidity rates, with nearly half of the affected patients experiencing permanent neurological impairment even after medical intervention. Given these risks, understanding the hemodynamic behavior of MCA aneurysms is crucial for improving treatment strategies. The MCA originates from the internal carotid artery and branches into four main segments, with the M1 segment extending from the carotid terminus to the first major bifurcation, where it divides into the M2 branches that supply the insular region before further branching into the M3 and M4 segments. Studies indicate that more than 60% of MCA aneurysms occur at the M2 bifurcation, making this location a critical focus for clinical and computational studies. Computational fluid dynamics (CFD) has been widely used to analyze hemodynamic parameters and predict post-treatment outcomes in various medical applications. In this study, five patient-specific models with aneurysms at the M2 bifurcation were analyzed, incorporating a porous medium approach to simulate endovascular coiling. We investigate the effects of outlet boundary conditions on blood flow dynamics in patient-specific cerebral aneurysm geometries. Unlike previous studies that assumed a laminar flow regime, this study accounts for arterial turbulence using the Low-Reynolds k–omega turbulence model, which is well-suited for cases where flow is mostly laminar but transition to turbulence occurs due to bifurcations or aneurysm sacs. Additionally, outlet boundary conditions were defined using the three-element Windkessel model to represent downstream vascular impedance more accurately. To ensure the reliability of our simulations, we implemented a mesh independence study based on the ASME recommended approach. For each subject, an initial computational mesh was generated, and the simulation was conducted while ensuring that the dimensionless wall parameter, Y-plus, remained within an acceptable range. Once validated, the total number of elements in the first mesh and the volume of the aneurysm geometry were used to systematically determine the total number of elements for subsequent meshes. By running additional simulations on these refined meshes, we confirm that our findings are not dependent on the mesh resolution and provide confidence in the accuracy of the hemodynamic predictions. In this study, CFD simulations were performed for both pre- and post-coil embolization scenarios to evaluate changes in flow characteristics and shear stress distributions. The results demonstrated that incorporating turbulence modeling and physiologically relevant boundary conditions provided a more precise representation of intra-aneurysmal flow dynamics. One of the primary goals was to study wall shear stress (WSS) within the aneurysm sac following coiling. By filling the aneurysm with coils, blood flow was disrupted, which substantially decreased the force exerted on the aneurysm walls. This reduction in WSS is crucial, as low WSS promotes aneurysm expansion and weakening of the vessel wall, whereas high WSS can trigger the initial damage that leads to aneurysm development. These findings show the importance of advanced CFD modeling techniques in improving the precision of hemodynamic evaluations for cerebral aneurysms, which contributes to patient-specific treatment planning. Incorporating turbulence modeling, pseudo-physiological boundary conditions, and mesh-independent CFD analysis enhances the reliability of simulations. This method, ultimately, supports more informed clinical decision-making for patients with MCA aneurysms.

Presenting Author: Mohammadali Monfared Mississippi State University

Presenting Author Biography: Mohammadali Monfared is a PhD student of Biomedical Engineering at Mississippi State University. He holds a master's degree in Mechanical Engineering with a focus on Energy Conversion and Fluid Mechanics from Shiraz University, and a Bachelor of Science in Mechanical Engineering with a specialization in Fluid Mechanics from Persian Gulf University.

Authors:

Mohammadali Monfared Mississippi State University
Kamryn Parks Mississippi State University
Luke Hollingsworth Mississippi State University
Judy Hung The Mississippi School for Mathematics and Science
Joey Knight The Mississippi School for Mathematics and Science
Peshala Thibbotuwawa Gamage Florida Institute of Technology
Amirtahà Taebi Mississippi State University