In this chapter we present a numerical model for the simulation of blood flow inside cerebral aneurysms. We illustrate the process of predicting flow and forces that arise in vessels and aneurysms starting from patient-specific data obtained using medical imaging techniques. Once the three-dimensional geometry is reconstructed, we discuss fluid properties of blood which allows to compute the flow. The flow of an incompressible Newtonian fluid in the human brain is simulated by using a volume penalizing immersed boundary method, in which the aneurysm geometries are represented by the so-called masking function. We impose pulsatile flow forcing, based on the direct measurement of the mean flow velocity in a vessel during a cardiac cycle and focus on effects due to changes in the flow regimes. In slow or very viscous flows the pulsatile forcing dominates the fluid dynamical response, while at faster or less viscous flows the intrinsic unsteadiness of natural incompressible flow is dominant over the pulsatile flow forcing effect. We consider a full range of physiologically relevant conditions and show high frequencies to emerge in the pulsatile response. The strong qualitative transitions in flow behavior and shear stress levels inside an aneurysm cavity at increased flow rates may contribute to the long-term risk of aneurysm rupture.
- Cerebral aneurysm
- Numerical simulation
- patient-specific modeling
- MACS-MMS: Multiscale Modelling and Simulation
- Pulsatile flow