Fluid-Structure Interaction of a Collapsible Thin-Walled Vessel under Steady and Pulsatile Flow Conditions

Fluid-structure interactions between pulsatile flow and collapsible vessels are common in physiological systems, such as large veins, pharyngeal canal, and pulmonary airways. The interactions exhibit rich non-linear unsteady behaviors including self-excited oscillations and internal flow instabilities. In this work, experiments were conducted to study the wall deformation and the fluid flow in a thin-walled vessel using the optical method and Particle Image Velocimetry. A Newtonian fluid mixture was used as a blood surrogate and the internal flow is simulated under both steady and pulsatile conditions. Both the internal pressure gradient and the transmural pressure were controlled. Our results suggest the vessel deformation follows Shapiro's tube law under stationary conditions. The maximum collapse location and cross-sectional area shift as Re and transmural pressure change. A critical transmural pressure range exists within which the self-excited oscillations occur. Both chaotic and cyclic oscillations have been observed. Under pulsatile flow conditions, the interaction behavior is significantly altered as a function of Re, Wo, pulsatility index, and transmural pressure. The study provides a benchmark for computational studies of pulsatile flow in complex collapsible vessels.