Experimentally Validated Hemodynamics Simulations of Mechanical Heart Valves in Three Dimensions

Abstract

Abstract-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 kÀ 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.

Non‐Newtonian Blood Flow Simulation of Diastolic Phase in Bileaflet Mechanical Heart Valve Implanted in a Realistic Aortic Root Containing Coronary Arteries

“…However, as time passes and the blood flow approaches its quasi-static state in leakage flow phase, the blood is directed to the coronary arteries and regurgitant jet reaches its constant value before the enddiastole. Therefore, the maximum leakage velocity occurred immediately after the valve closure and is approximately 4 m/s which is in agreement with experimental data (44). In addition the LAD mean flow rate is about 120 mL/min which is in the same order with the reported value for the optimal orientation of the mechanical valve (35).…”

A novel computational model for the hemodynamics of bileaflet mechanical valves in the opening phase

“…Pressure inlet and turbulent profile inlet have very similar results as the regime of the flow is turbulent, while uniform velocity inlet shows a different pattern. Results from Ge et al 8 show the maximum velocity at the lateral orifices, while Nguyen et al 18 reported these velocities approximately at the same level and the same pattern as the uniform velocity inlet did. Both of these studies have considered an axisymmetric sinus, while the current study considers physiological sinuses with the long inlet and outlet lengths far enough from the leaflets to let the flow develop a zero gradient velocity and pressure at the inlet and/or outlet boundaries.…”

“…Additional studies reinforce the idea that maximum velocity does not emerge from the lateral orifices. [16][17][18] As to the profile of velocity downstream of the leaflets, some studies reported a semi-flat shape velocity profile downstream of the valve at the main and lateral orifices, 12,16,17 while other studies showed a curved profile with the maximum at the center. [6][7][8][9]11,13 The peak velocity in these studies ranges from 1 to 3 m/s, which highly depends on the model's assumptions and numerical setups, such as the geometry of the valve and the aortic root, BCs, and regime of flow.…”

Numerical investigation on effect of leaflet thickness on structural stresses developed in a bileaflet mechanical heart valve for its sustainable manufacturing

“…Their results were found in good agreement with experimental measures. It's important to note that due to large structural displacements involved while simulating BMHV, subsequent remeshing and smoothing is required to maintain a good quality mesh [10].…”