Response of a collapsible tube carrying flow with and without stenosis*

Arterial stenosis is the constriction in arteries caused by the growth of plaque and can lead to many cardiovascular health issues. A deformable tube with internal constriction and internal flow is a very complicated fluid-structure interaction problem. We experimentally investigate the dynamics of a collapsible latex tube carrying flow and subjected to a constant external pressure of 700 Pa, with a thermocol ball (25 mm diameter) pasted to the internal surface of the flexible wall. Tube response is measured using high-speed photography with two locations of the constriction, namely L/2 and L/4 from the upstream end (L is the length of the collapsible tube). Without constriction, the tube exhibits collapsed states, self-excited milking (periodic/aperiodic) oscillations and distended states, as the Reynolds number increases. With constriction, aperiodic high-amplitude milking oscillations are completely absent. However, high-frequency low-amplitude fluttering is observed at higher Reynolds number when the constriction is at L/2, due to increased tension in the tube wall. Flow visualization shows the presence of strong recirculation upstream of the constriction, indicating significant viscous dissipation and pressure drop across the stenosis, suppressing the milking oscillations.