Self-excited oscillations of three-dimensional collapsible tubes conveying both laminar and turbulent flows

Abstract

This study investigates self-excited oscillations of three-dimensional collapsible tubes conveying both laminar and turbulent flows, using an immersed boundary-lattice Boltzmann method. The effects of Reynolds number (Re) on these oscillations are explored, revealing that at Re = 200, periodic vortex shedding downstream of the tube throat induces small-amplitude, quasi-periodic self-excited oscillations. Notably, stress concentrations near the downstream end of the elastic tube lead to the formation of two regions of wall thickening, which may predispose the elastic tube to fatigue failure. At higher turbulent flow conditions (Re = 1000), flow bifurcation occurs, resulting in large-amplitude, quasi-periodic oscillations. These oscillations are similarly driven by vortex shedding, which imparts periodic perturbations onto the elastic tube wall. Additionally, analysis at two monitoring points within the downstream rigid tube reveals small secondary oscillations in pressure and streamwise velocity. These secondary oscillations are attributed to the merging jets and their interactions within the downstream rigid tube.