An experimental study of fluid-structure interaction and self-excited oscillation in thin-walled collapsible tube

Flow through thin-walled collapsible tubes often exhibits a complex nonlinear interplay between fluid dynamics and structural mechanics. This paper presents findings from an experimental investigation employing quantitative analyses of structural deformation and flow fields through image analysis and particle image velocimetry (PIV) measurements. The results suggest that as Reynolds number (Re) increases, the tube experiences buckling and collapses under greater negative transmural pressures (P-tm) compared with no flow condition, indicating that increasing flow inertia delays the onset of collapse. The onset of self-excited oscillation is marked by a Re threshold. Beyond this threshold, self-excited oscillations occur within a specific range of P-tm. Small-amplitude, chaotic oscillations emerge at relatively low Re or when P-tm approaches the upper limit of the oscillation-inducing regime. Conversely, large-amplitude, periodic oscillations arise as Re increases and P-tm decreases. The frequency of oscillation escalates with increasing Re and decreasing P-tm, while amplitude peaks near the midpoint of the oscillation-inducing P-tm range. PIV results indicate that large-amplitude, periodic oscillations correlate with asymmetric jet flows that switch directions from cycle to cycle. Furthermore, self-excited oscillations reduce overall flow resistance, thereby mitigating flow limitations under highly negative P-tm. These findings contribute to a deeper understanding of collapsible tube dynamics under varying flow conditions, with implications for diverse fields ranging from biomedical engineering to space physiology.