Patterns of pulsatile flow in arterial models with stenosis

Pulsatile flow in arterial models with an axisymmetric or nonsymmetric stenosis was visualized to investigate the pattern of streamlines and the mode of vortex formation. In a model with an axisymmetric constriction, a decrease in the constriction ratio or a rise in the Reynolds number decreased the magnitude of the acceleration number, which was an index to the unsteadiness of the flow, and facilitated the repetitive shedding of vortex rings which in turn led to the generation of turbulence. The presence of an oscillatory component in flow velocity altered the pattern of steady flow around a non symmetric constriction, which was characterized by a pair of standing vortices behind and a stationary horseshoe vortex in front of the obstacle. In pulsatile flow, nonsymmetric vortex rings were generated periodically behind the obstacle and shed down-stream in succession, and periodical changes also were observed in the position and width of the horseshoe vortex.