Analysis of the unsteady flow in an elastic stenotic vessel

Stenosis strongly alters the flow field inside a blood vessel not only through geometric changes but also due to changing the mechanical properties of the vessel. Since the flow field has via, e.g., the oscillating wall-shear stress (WSS), a significant effect on the pathogenesis of atherosclerosis a better understanding of the unsteady velocity field and the fluid-structure interaction is necessary. Time-resolved particle-image velocimetry (TRPIV) is combined with simultaneous measurements of the static pressure inside an elastic, axisymmetric stenosed, transparent vessel at pulsatile flow in a range of Reynolds numbers 310≤ReD≤690 and Womersley numbers 7.5≤Wo≤13. The location of the elastic wall and the near-wall velocity distribution is highly resolved to determine the unsteady WSS. The effect of the vessel elasticity on the flow is analyzed by the velocity distribution, the vessel dilatation, and the static pressure. At dilatations of the vessel model up to 5% the measurement quantities exhibit phase lags and deviations from the temporal bulk flow distribution which depend on the exciting frequency. Below the eigenfrequency local dilatation and static pressure are in phase. Above the eigenfrequency a higher mode oscillation superimposed onto the bulk flow in the throat region of the stenosis exits which is caused by a phase shift in the dilatation on both sides of the stenosis. The TRPIV measurements show the stenosis to induce a jet through the throat together with complex flow structures like ring vortices. The unsteady footprints of these structures are evidenced by oscillating WSS distributions which also aggravate stenosis.