Waveform dependence of pulsatile flow in a stenosed channel.

Bloodflow in arteries often shows a rich variety of vortical flows, which are dominated by the complex geometry of blood vessels, the dynamic pulsation of blood flow, and the complicated boundary conditions. With a two-dimensional model of unsteady flow in a stenosed channel, the pulsatile influence on such vortical fluid dynamics has been numerically studied in terms of waveform dependence on physiological pulsation. Results are presented for unsteady flows downstream of the stenosed portion with variation in the wavefiorms of systole and diastole. Overall, a train of propagating vortex waves is observed for all the cases, but it shows great sensitivity to the waveforms. The generation and development of the vortex waves may be linked to the presence of an adverse pressure gradient within a specific interval between two points of inflection of the systolic waveform. The adverse pressure gradient consists of a global pressure gradient that is found to be closely related to the dynamnics of' the pulsation, and a local pressure gradient, which is obsented to be dominated by the nonlinear vortex dynamics.