Computational investigation of pulsatile flows and wall stresses in models of abdominal aortic aneurysms

Flow field computations are presented for flow through a series of abdominal aortic aneurysms (AAA) models, and compared with earlier experimental results. A set of rigid models with elliptical geometry was constructed and both steady and pulsatile flows simulating in vivo aortic rest conditions were delivered through the models. Velocity and pressure fields were established by solving the Navier-Stokes equations under no-slip boundary conditions and entrance and exit conditions suitable for fully developed flow, using commercial finite volume software. During systole, there was a strong forward flow in the core, largely without recirculation in the bulge. As the flow then reversed, the velocity became retrograde throughout the model. Shear stresses were largest in intermediate sized models, which is explainable by comparing vorticity diffusion times with the flow period. The wall pressure variation along the bulge was less than 2 mmHg, regardless of the flow phase or model size, but varied by 125 mmHg. over the cycle. This suggests that AAAs in vivo are exposed to strong variations of pressure even at rest