Direct numerical simulations illustrate aberrant blood flow contributing to brain aneurysms

Brain aneurysms arise from focal weaknesses in the blood vessel walls, leading to uncontrolled expansion prone to life-threatening rupture. While blood flow in aneurysms is thought to be significant, understanding its exact role has been hampered by difficulty in measuring and interpreting the associated hemodynamics. New work in simulating the changes in blood flow looks to shed new light on these potentially devastating conditions.

Researchers have conducted direct numerical computational fluid dynamics simulations to better separate potentially pathologic blood flow patterns within aneurysms from physiologic ones. Using a combination of spectral proper orthogonal decomposition and phase-averaging techniques on the OpenFOAM computational fluid dynamics software, Luciano et al. can decompose, or break down, the velocity and wall shear stress fields in simulated diseased cerebral arteries into collections of flow patterns and features.

The techniques provide a new way to separate the base pulsatile and physiological laminar flow from the turbulent fluctuations.

“This separation may be helpful and have implications toward the clinical assessment of this disease, as these different structures may have different effects on the arterial walls,” said author Rafaello Duarte Luciano. “The blood flow rates in these arteries are very low, which would indicate that the flow should be simple and organized, yet the results show a very complex and disorganized flow.”

By differentiating between repeatable laminar flow structures from chaotic, turbulent ones, the group identified two vortical structures in the mean flow, as well as a significant flow frequency peak near 25 hertz that may stress the walls of blood vessels.

The group hopes their findings stoke future work in decomposing higher frequencies and lower energy flow structures, as well as more diverse aneurysm geometries.

Source: “Decomposition of blood flow in a cerebral artery with an aneurysm,” by R. D. Luciano, X. B. Chen, and D. J. Bergstrom, Physics of Fluids (2025). The article can be accessed at https://doi.org/10.1063/5.0270253 .