Computational fluid–structure analysis of the impact of leaflet thickness and protrusion height on the flutter phenomenon in aortic valve bioprostheses

Although it is associated with the low lifetime of aortic valve bioprostheses, flutter has little been studied in the dynamics of these valves. To improve the understanding of flutter in bioprosthetic leaflets, the present work evaluates the effect of leaflet thickness and protrusion height on flutter parameters through the computational fluid–structure interaction. A bioprosthesis geometry, based on a geometric model available in the literature, and a simplified fluid domain were developed. As a boundary condition, a parabolic velocity profile was applied at the inlet, outflow at the outlet, and fixed support at the sides of the leaflets. The valve cusps were considered with linear elastic and isotropic mechanical behavior, while the blood was modeled as a Newtonian fluid. Turbulence was modeled according to the k- ω SST model. The numerical results showed that, due to the occurrence of leaflet oscillations, both fluid dynamic quantities, such as pressure, velocity, and turbulence intensity, and solid domain quantities, such as stress and strain, exhibited an irregular and oscillatory behavior. Furthermore, the radial displacements of the leaflets were asynchronous, and the phase difference between the leaflets increased with increasing thickness. The frequencies ranged from 28.3 to 36.7 Hz, while the amplitudes ranged from 5.34 to 6.53 mm, where the valve with the lowest protrusion height did not develop flutter