Pulsatile flow in cerebral aneurysms

We develop a computational method for the simulation of the flow of blood through cerebral aneurysms, which may occur in the human brain. These aneurysms are weak regions in the vessel, presenting a serious risk of rupture to the patient. The goal is to understand the flow in these diseased parts of the vessel system. An immersed boundary method, based on volume penalization, is developed to compute the pulsatile flow. The raw medical imagery representing the patient-specific geometry is processed to extract the ‘masking function’, which is needed to simulate flow patterns and obtain wall shear stresses under realistic physiological conditions. We illustrate the numerical method for several model and realistic aneurysms. In each case we observe a transition to complex time-dependent flow in case the flow speed and/or the aneurysm size become sufficiently large. High frequency variations appear in the flow, which may be an easy method for monitoring the progress of a developing aneurysm and the risk it represents.