Numerical simulations of flow in flared sections of the human infrarenal aorta

The formation of separation zones in arteries may have important implications in the development of atherosclerotic lesions. It is known that arteries flare proximally to bifurcations where atherosclerotic lesions develop. Flow through an axisymmetric flared cylinder, which simulated the human infrarenal aorta, was studied using FIDAP, a finite element analysis program. Blood was assumed to have Newtonian properties while the flow was assumed to be steady and laminar. The wall of the artery was considered to be rigid. For this study, the angle of flare was varied from 1° to 5° with an inlet to outlet diameter ratio of 0.33. Reynolds numbers for the simulation ranged from 100 to 1000. A critical Reynolds number existed below which no separation zone was formed. At Reynolds numbers greater than this critical value, recirculation zones formed downstream of the flare. A linear relationship was observed between the length of the recirculation zone and the Reynolds number. There was an inverse, non-linear relationship between the critical Reynolds number and the flaring angle. The length of the recirculation zone was more sensitive to changes in Reynolds numbers at higher flaring angles