Blood Flow In Aneurysm With Magnetic Field CFD Simulation, ANSYS Fluent Tutorial

The study of blood flow dynamics within brain aneurysms has received greater attention, particularly in relation to the impact of magnetic fields present during diagnostic methods such as Magnetic Resonance Imaging (MRI). Brain aneurysms, which are characterized by unusual dilations of cerebral blood vessels, pose major health hazards, with rupture resulting in serious problems such as hemorrhagic stroke. While MRI is an important diagnostic tool for aneurysm diagnosis and monitoring, the intense magnetic fields created by MR scanners (usually 1.5-3 Tesla) must interact with the circulating blood, which contains electrically charged particles. This magnetohydrodynamic (MHD) effect may modify blood flow patterns within the aneurysm, resulting in a complex interaction between diagnostic need and flow dynamics. For deeper understanding, a CFD study is performed based on a reference paper titled “Blood flow computational characterization inside an idealized saccular aneurysm in presence of magnetic field [1]”.

• Reference [1]: Cardona Taborda, Melisa. Blood flow computational characterization inside an idealized saccular aneurysm in presence of magnetic field. Diss. 2019.
• Reference [2]: Mehra, Manik, et al. “Intracranial aneurysms: clinical assessment and treatment options.” Biomechanics and Mechanobiology of Aneurysms(2011): 331-372.
• Reference [3]: Xu, Jinyu, et al. “Combined effects of flow diverting strategies and parent artery curvature on aneurysmal hemodynamics: a CFD study.” PloS one9 (2015): e0138648.

Figure 1: Most common saccular aneurysm sites in Circle of Willis [1]

Simulation Process

Figure 2 shows a rebuilt 3D model of a saccular brain aneurysm in the anterior communicating artery (ACoA) with a curvature of 60º, based on the most prevalent disease location. The model then divided by Polyhedra cells in Fluent Meshing software. Given the non-newtonian blood nature, Herschel–Bulkley model is considered for the dynamic viscosity that varies. Magnetic hydrodynamics (MHD) is a method for modeling the behavior of electrically conducting fluids under magnetic fields. Additionally, the Navier-Stokes equations are used to simulate laminar, transient, and incompressible blood flow, together with MHD equations. Last but not the least, a velocity profile is utilized to adopt pulse blood flow from inlet boundary.

Figure 2: 3D model of a Saccular Brain Aneurysm for CFD simulation [1]

Post-processing

The numerical simulation shows detailed flow patterns and electromagnetic interactions inside the aneurysm geometry. The velocity magnitude contours reveal peak values of 1.12 m/s along the main vessel walls, followed by considerable slowdown in the aneurysm dome. This flow behavior is consistent with the static pressure distribution, indicating a steady pressure decline from the inlet pressure of 1869.21 Pa. The current density magnitude reaches 2.0e+04 A/m² between the artery walls and aneurysm neck, showing substantial electromagnetic coupling in these areas. The magnetic field distribution peaks at around 5.0e+04 tesla along the curving vessel walls, with significantly lower intensities in the aneurysm dome, whereas the electric field has a more uniform distribution pattern, with maximum values reaching 1.12 V/m.

Figure 3: Velocity field, current density and magnetic field in Aneurysm

The wall shear stress (WSS) analysis revealed considerable differences between locations, with the aneurysm dome having significantly lower WSS (0.106 Pa) than the neck region (4.013 Pa) and the main blood vessel (14.69 Pa). This significant variation in WSS readings implies the possibility of flow standstill in the dome and increased flow activity in the main vessel. The force magnitude contours show maximum values of 2.0e+04 N/m³ in the main vessel and neck regions, indicating the sites with the strongest electromagnetic interactions. These findings emphasize the complicated interplay between hemodynamics and electromagnetic effects, particularly in crucial locations like the aneurysm neck, which could have far-reaching consequences for diagnostic imaging and therapeutic approaches.