Experimentally Validated Hemodynamics Simulations of Mechanical Heart Valves in Three Dimensions

摘要

Mechanical heart valves (MHV) have been widely deployed as a routine surgical treatment option for patients with heart valve diseases due to its durability and performance. Understanding hemodynamics of MHV plays a key role in performance assessment as well as design. In this work, we propose a numerical method for simulations of full three dimensional MHV with moving valve leaflets in a typical human cardiac cycle. A cell-centered finite volume method is employed to model incompressible flows in MHV. As the flow experiences from laminar to turbulence over every cardiac cycle, the unsteady Reynolds average Navier-Stokes (URANS) equations is solved with κ-ε and Spalart-Allmaras turbulence models to resolve large scaled turbulent eddies in high Reynolds number flow regimes. URANS approach chosen for the balance of turbulence resolution and computational cost shows good agreement with more detailed turbulence models as well as experimental data. For capturing the large amplitude movement of the valves, we develop an optimization-based moving mesh technique with objective functions operating on different mesh quality metrics. The method is capable of extensively providing an effective way to maintain and improve the mesh quality due to large movement of domain boundaries. The numerical results for laminar and turbulent flows are validated against experimental data using Particle Image Velocimetry technique. The simulation is able to capture essential features of flows in MHV. The triple jet structure is observed in the simulations together with a switching of central orifice jet flow from horizontal axis to vertical axis downstream of the leaflets and the results are well compared with the experimental data. The moving mesh technique has enabled us to simulate a whole cardiac cycle with pulsatile physiological conditions and prescribed motions of the leaflets. The simulations can essentially reproduce the varying pressure profiles at the left ventricle and aorta. The wall shear stress and vorticity can then be deduced from the simulation results to further access the valve performance. This study also constitutes an important step towards understanding hemodynamics in MHV and contributing to the advancement in study of improved MHV.