Fluidstructure interaction, immersed boundary-finite element method simulations of bio-prosthetic heart valves
A three-dimensional fluidstructure interaction (FSI) framework for rigid bodies has been extended to deformable soft tissue by coupling a sharp-interface immersed boundary incompressible NavierStokes solver for fluids with a non-linear large deformation finite element method for soft tissue. A Fung-type constitutive law is used for the soft tissue of heart valves that can capture the experimentally observed non-linear anisotropic stressstrain behavior of the heart valve tissue. The FSI solver adopts a strongly-coupled partitioned approach that is stabilized with under-relaxation and the Aitken acceleration technique. The finite element solver is verified against the benchmark experimental and numerical data for heart valve tissue while the immersed boundary solver was validated against flow measurements of a mechanical heart valve in the previous work. The capabilities of the solver are demonstrated by simulating the first fully three-dimensional fluidstructure interaction of tissue valves implanted in the aortic position during systole under physiologic flow conditions. It is observed that the flows threefold symmetry breaks during the early systole, questioning the threefold symmetry assumption of previous simulations. The flow created by the tissue valve is compared against the mechanical heart valve under the same conditions. The flowfields, created by the tissue and mechanical valves, show drastic differences at different instances during a heartbeat cycle. Mainly, the breakdown of vortices into small-scale vortical structures right before the peak systole in mechanical heart valves is not observed in the bio-prosthetic heart valves.
fluidstructure interaction finite element method heart valve immersed boundary method