Boundary conditions for flow simulations of abdominal aortic aneurysms

Abstract

Boundary conditions for abdominal aortic aneurysm simulations are problematic both on the fluid and the solid side. In this paper improvements are suggested on existing methodology in both respects.First, a derivation of a hyperelastic wall model is given, taking into account the wall stresses at the diastolic instant. It is demonstrated that this model can be approximated with a simplified linear wall model in the physiologically interesting range.Then a new method for inlet and outlet boundary condition generation is introduced on the fluid side, based on a one-dimensional transient simulator. Finally, the effect of spine support on the intra-aneurysmal flow is studied.Good agreement was found between rigid wall flow simulations on the “systolic” geometry and the fluid–structure interaction simulations. Other authors found much larger differences because earlier the “diastolic” geometry had been used for comparisons and the stresses in the diastolic state were neglected. It was concluded that the spine support does not have a great impact on the flow field. Significant differences were found between the flow behaviour of artificially generated and real aneurysm geometries.