Interactions between non-newtonian blood flow and deformable walls of a patient-specific aneurysm

Abstract

The movements of the walls of a patient-specific cerebral aneurysm were studied by using fluid–structure interaction approach, where the non-Newtonian blood flow was modeled through the Casson viscosity model and its interactions with the deformable dome were modeled using the finite element method. The coupling was achieved using the preCICE multi-physics toolkit, applying an Arbitrary Lagrangian–Eulerian formulation with Interface Quasi-Newton with Inverse Jacobian from a Least-Squares acceleration for optimum convergence. Given the complex geometry of aneurysms, the Nearest Projection mapping technique was used to handle non-conformal fluid-solid interfaces with enhanced numerical accuracy. Results showed that the uniformity of the flow field seems to be critically important, and its degradation leads to the high values of the von Mises stresses, which in turn lead to high wall displacements. The spatial distribution of the von Mises stress also puts evidence that the maximum values of the von Mises stress exactly coincide with the highest oscillatory shear index and relative residence time, accompanied by the lowest time-averaged wall shear stress values. Furthermore, it is shown that these locations generally overlap with the flow impingement zone. Indeed, during the pulsation cycle, the locations of the maximum displacements ramble around the surface of the dome but are often concentrated over the region of the impingement. This study provides novel results regarding the dynamic wall response of cerebral aneurysms under physiological conditions, highlighting the effects of hemodynamic variations on structural degradation.