Comparison of Navier-Stokes and lattice Boltzmann solvers for subject-specific modelling of intracranial aneurysms

Modelling cardiovascular disease is at the forefront of efforts to use computational tools to assist in the analysis and forecasting of an individual's state of health. To build trust in such tools, it is crucial to understand how different approaches perform when applied to a nominally identical scenario, both singularly and across a population. To examine such differences, we have studied the flow in aneurysms located on the internal carotid artery and middle cerebral artery using the commercial solver Ansys CFX and the open-source code HemeLB. This comparison evaluates both the algorithmic methods used (finite volume method and lattice Boltzmann method) and issues surrounding the preparation and execution of a simulation using a commercial solver and an academically developed code. We compare velocity profiles within the domain and common metrics used to assess aneurysm rupture risk across a population of 462 boundary condition profiles. Generally, the flow computed by the solvers is qualitatively quite similar in the two domains. The momentum driven flow in the middle cerebral aneurysm demonstrated good quantitative agreement for velocity and shear stress-based metrics throughout the aneurysm region. Although there was greater quantitative variation in the shear driven internal carotid aneurysm, both methodologies consistently identified locations of extreme values of metrics associated with aneurysm rupture risk. Whilst each method has respective advantages and disadvantages that would influence the choice of tool deployed by a particular user, either can provide useful numerical information about flow in an aneurysm to guide decision making in a clinical scenario.