An Experimental Study of Pulsatile Flow and Structural Dynamics in a Thin-Walled Collapsible Vessel

Abstract Many physiological fluid transport phenomena exemplify the complex fluid-structure interaction in collapsible tubes. For example, microgravity during space travel associates physiological challenges, as it alters hydrostatic and transmural pressures, causing irregular blood flow and venous thrombosis in veins. To further our understanding of the collapsible tube behavior under both steady and pulsatile flow conditions, an experimental study was presented in this paper. The study employed quantitative analysis of structural deformation and flow fields using image analysis and Particle Image Velocimetry (PIV) measurements. The results suggest that the tube wall deformation followed Shapiro’s tube law under static condition and conformed under steady flow condition. However, as Re increased above 1150, self-excited oscillations occurred in an irregular pattern within specific ranges of negative transmural pressures. These oscillations became stronger and more regular as Re further increases, with frequency increasing as transmural pressure became more negative. With pulsatile flow inputs, negative transmural pressures also led to periodic self-excited oscillations during each cycles, particularly towards the end of systolic phases. Flow limitation effects were observed, with self-excited oscillations enhancing peak flow rates under strongly negative transmural pressures. The study suggests that self-excited oscillations could be triggered by either steady flow and pulsatile flow inputs within optimal transmural pressure ranges. In pulsatile flows, a negative transmural pressure aids in maintaining positive pressure gradients, acting similarly to valves to prevent flow reversal.