ANEURYSM HAEMODYNAMICS Undesirable Haemodynamics in Aneurysms

Abstract. A computational fluid dynamics study is employed to investigate the flow within an idealized fusiform aneurysm. The model includes sections of the arteries upstream and downstream of the aneurysm, which is modeled as an elliptical bulge of a shape consistent with both previous experimental studies, and accepted values for aneurysms located on the human abdominal aorta. Flow is assumed axisymmetric and Newtonian, allowing efficient computation in cylindrical coor-dinates. Results are reported for both a steady-state inflow, as well as time-varying inputs with frequencies selected to represent heart rates ranging from rest to strenuous exercise. The effects of these parameters on the dynamics of the flow within the aneurysm are reported, as is variation in the resistance to flow when compared with an undeformed artery of the same length. The rate at which fluid is flushed from an aneurysm is found to be strongly dependent on the frequency of the pulsatile flow, but independent of geometrical features such as the radius of curvature at the junction between the artery and the aneurysmal bulge. Wall shear stress and pressure drop across the aneurysm are found to be sensitive to these geometrical alterations, although in the case of the pressure drop the changes are insignificant as the resistance to flow is predicted to be lower in the aneurysm than in an undamaged artery of the same length