Numerical simulations of time-dependent, non-Newtonian blood flow through typical human arterial bypass grafts

The development of the detrimental feature of intimal hyperplasia at the locations where bypass grafts are surgically attached to host arteries is believed to be promoted by haemodynamic factors. Thus, it is of interest to model the flow of blood through typical arterial bypass configurations in order to identify which features of the flow field encourage the progression of the disease. Computational Fluid Dynamics (CFD) simulations of the non-Newtonian flow of blood through typical three-dimensional human femoral artery bypass graft models have been performed. The complete bypass configuration, rather than just the proximal or distal junction in isolation, has been analyzed. Steady flow studies verified the strong dependence of the anastomotic flow field on the problem geometry. Flow disturbances were minimized at low anastomotic angles. A pulsatile flow computation, using a realistic femoral artery flow pulse, demonstrated noteworthy temporal and spatial variations in the flow fields at the proximal and distal anastomoses during the cardiac cycle. Due to the oscillations in direction of the flow at the distal anastomosis, and given the persistent zones of low momentum recirculating fluid, it is concluded that fluid particle residence times in the neighbourhood of the distal anastomosis are high. This feature may be of significance with regard to haemodynamic mechanisms for intimal hyperplasia