Anomalous stability behaviors in two-sided wavy collapsible channels

Stents have been extensively used to handle the severe stenosis of arteries. The properties of the stented arteries have not been carefully studied. This study investigates the dynamic behaviors of two-sided wavy collapsible channels conveying a pulsatile flow by using the immersed boundary-lattice Boltzmann method. A pulsatile flow representing heartbeats and a simplified wavy wall modeling the stent geometry are incorporated, along with two configurations: wall movement with and without a symmetric constraint. The fluid–structure interaction system is solved by a hybrid method of the immersed boundary-lattice Boltzmann and the generalized interpolation material point methods. Several key parameters are analyzed: Reynolds number (Re), non-dimensional frequency, external pressure, mass ratio of the wall, and the constraint of flexible walls. It is found that the chaotic paths of systems with and without the symmetric constraint are opposite within the ranges of the parameters considered here, which may be due to the energy input associated with the constraint. Specifically, for channels without the constraint, the flow goes from periodic to quasiperiodic and then chaotic when Re, and the pressure ratio decrease; while the system with the constraint experiences such changes when Re, and the pressure ratio increase. Moreover, increasing the frequency of the pulsatile flow shows a transition from quasiperiodic to chaotic behavior for both systems with and without constraint, which is due to the shift of the phase between the flow pressure and the wall movement from almost in phase for the quasiperiodic cases to anti phase for the chaotic cases. The results obtained in this work can be used to plan and evaluate the stent insertion. The two-dimensional simulation is considered due to its low computational cost and its ability to reveal the major mechanisms. It is beneficial to study the three-dimensional cases with contact models between the stent and the artery in the future.