Two fluid-structure approaches for 3D simulation of St. Jude Medical bileaflet valve opening.

Abstract

This paper deals with the three-dimensional (3D) numerical simulation of the opening transient for a bileaflet mechanical heart valve (St. Jude Medical Hemodynamic Plus, 27 mm characteristic size). The discussion concerns two different types of ""partitioned"" fluid-structure models, with weak and strong coupling. Both approaches are based on a moving deforming mesh method as implemented in the CFD commercial software Fluent (Fluent Inc., USA), and both yielded dynamically consistent results from a quantitative viewpoint. There is a slight improvement (peak relative difference <1%) of the numerical solution (angles vs. time) when using the strong instead of the weak coupling model. This is of utmost importance when the considerable reduction of the computational costs for the weak scheme (about 60% less) is taken into account. However, the strong coupling model provides a more consistent physical description of the interaction when looking at small-scale features like stress close to geometrical singularities. In the experiments, the differences both in terms of time-to-peak delay (15% of the opening time) and in terms of underestimation of the peak velocity (8%) seemed due to defects in the fluid inertia assessment, which depends on initial and boundary data.