Abstract
The work is focused on calculating hemodynamically negative effects of a flow through bileaflet mechanical heart valves (BMHV). Open-source FOAM-extend and cfMesh libraries were used for numerical simulation, the leaflet movement was solved as a fluid-structure interaction. A real model of the Sorin Bicarbon heart valve was employed as the default geometry for the following shape improvement. The unsteady boundary conditions correspond to physiological data of a cardiac cycle. It is shown how the modification of the shape of the original valve geometry positively affected the size of backflow areas. Based on numerical results, a significant reduction of shear stress magnitude is shown. The outcome of a direct numerical simulation (DNS) of transient flow was compared with results of low-Reynolds URANS model k-ω SST. Despite the limits of the two-dimensional solution and Newtonian fluid model, the suitability of models frequently used in literature was reviewed. Use of URANS models can suppress the formation of some relevant vortex structures which may affect the BMHV’s dynamics. The results of this analysis can find use in optimizing the design of the mechanical valve that would cause less damage to the blood cells and lower risk of thrombus formation.
Highlights
Heart valves regulate the direction of blood flow in heart chambers
Open-source FOAM-extend and cfMesh libraries were used for numerical simulation, the leaflet movement was solved as a fluid-structure interaction
Since several works resolves the platelet activation along chosen trajectories [2, 5, 6], both the shear stress values and the trajectory shape would have been affected and the results devaluated if URANS modeling was used
Summary
Heart valves regulate the direction of blood flow in heart chambers. During severely pathological states of the valves, such as aortal stenosis or mitral regurgitation, their replacement with artificial implants may be unavoidable. With the current trend of population aging, it is estimated that the current number of 280 000 heart valve transplantations per year will triple over the 30-year period [1]. It can be assumed that the requirements for the lifetime span of the artificial valves will further increase. The artificial replacements can either use biological tissues or rely purely on mechanical design. The tissue-engineered heart valves generally reach better hemodynamic properties, their usage is limited by a relatively short lifetime. Mechanical valves have a stable role in cardiovascular surgery for patients with a longer life expectancy
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