Unsteady forces and vortices of an aortic valve from 3D FSI simulation

There have been a few numerical studies of 3D FSI of the aortic valve, but information about the forces on the valve and the unsteady vortices in the flow is still rare.  We developed a 3D FSI model of a bioprosthetic aortic valve and solved the flow using an immersed-boundary method that is parallelized using domain decomposition.  The flexible leaflets of the valve were modeled as the hyperelastic Saint Venant-Kirchhoff material and were discretized using 20-node hexahedral elements. The simulation was able to capture both realistic deformation of the leaflets and vortex structures in the flow, thus providing a balanced modeling approach for the flow and the valve.  The results show that the pressure distribution on the leaflet surface is highly nonuniform during both opening and closing, and that the jet flow contains a sequence of vortices during the opening process and later experiences significant oscillations. The drag resistance of the valve when it is being pushed open is approximately equivalent to the inertial force of accelerating the fluid column of three diameter length.  The “water hammer effect” was also captured, which produces a high peak force on the valve after closure.  These details could be potentially used to characterize FSI of the aortic valve.