Pulsatile flow hemodynamics in common iliac arteries: effect of bifurcation angles

Arterial bifurcation geometry plays a critical role in modulating local hemodynamics and the development of atherosclerosis, particularly in the iliac arteries, where variations in bifurcation angle can induce disturbed flow. In this study, three-dimensional iliac artery models with bifurcation angles of 30°, 45°, and 60° were analyzed using computational fluid dynamics under physiologically realistic pulsatile, non-Newtonian blood flow conditions. Transient simulations were performed assuming rigid vessel walls and no-slip boundary conditions, and key hemodynamic indices, including wall shear stress (WSS), oscillatory shear index (OSI), relative residence time (RRT), and vortex structures, were evaluated over a complete cardiac cycle. The results demonstrate a strong dependence of flow behavior on bifurcation angle. The 30° model exhibited predominantly streamlined flow with localized vortices, elevated WSS (~ 5.2 Pa), and low OSI (~ 0.1). Increasing the angle to 45° led to expanded vortex regions, reduced WSS (~ 2.5 Pa), and increased OSI (~ 0.22), indicating transitional flow behaviour. The 60° configuration showed pronounced flow separation, minimal WSS (~ 0.5 Pa), high OSI (~ 0.35), elevated RRT, and widespread low-magnitude, highly oscillatory shear, with vortical structures becoming more prominent during diastole. Secondary bifurcations further amplified upstream disturbances and altered downstream separation patterns. These findings demonstrate that larger iliac bifurcation angles promote atheroprone hemodynamic environments characterised by reduced WSS and increased oscillatory shear, highlighting the importance of vascular geometry in disease risk assessment and intervention planning.