Transitional flow in intracranial aneurysms - a space and time refinement study below the Kolmogorov scales using Lattice Boltzmann Method

TL;DR

This study uses high-resolution Lattice Boltzmann simulations to investigate transitional flow in intracranial aneurysms, revealing flow transition behavior at Reynolds numbers and providing detailed turbulence quantification below Kolmogorov scales.

Contribution

It demonstrates the capability of standard Lattice Boltzmann methods to capture transitional flow in aneurysms at unprecedented resolutions, challenging previous assumptions of laminar flow.

Findings

Transition occurs at specific Reynolds numbers in aneurysms.

High-resolution simulations reveal turbulence characteristics below Kolmogorov scales.

Flow transition depends on aneurysm geometry and inflow conditions.

Abstract

Most Computational Fluid Dynamics (CFD) studies of hemodynamics in intracranial aneurysms are based on the assumption of laminar flow due to a relatively low (below 500) parent artery Reynolds number. A few studies have recently demonstrated the occurrence of transitional flow in aneurysms, but these studies employed special finite element schemes tailored to capture transitional nature of flow. In this study we investigate the occurrence of transition using a standard Lattice Boltzmann method (LBM). The LBM is used because of its computational efficiency, which in the present study allowed us to perform simulations at a higher resolution than has been done in the context of aneurysms before. The high space-time resolutions of 8{\mu}m and 0.11 {\mu}s resulted in nearly one billion cells and 9 million time steps per second and allowed us to quantify the turbulent kinetic energy at resolutions below the Kolmogorov scales. We perform an in-depth space and time refinement study on 2 aneurysms; one was previously reported laminar, while the other was reported transitional. Furthermore, we investigate the critical Reynolds number at which the flow transitions in aneurysms under time constant inflow conditions.