The upstream boundary condition influences the leaflet opening dynamics in the numerical FSI simulation of an aortic BMHV

Abstract

SUMMARYIn this paper, the influence of the upstream boundary condition in the numerical simulation of an aortic bileaflet mechanical heart valve (BMHV) is studied. Three 3D cases with different upstream boundary conditions are compared. A first case consists of a rigid straight tube with a velocity profile at its inlet. In the second case, the upstream geometry is a contracting left ventricle (LV), positioned symmetrically with respect to the valve. In the last case, the LV is positioned asymmetrical with respect to the valve. The cases are used to simulate the same 3D BMHV. The change in time of the LV volume is calculated such that the flow rate through the valve is identical in each case. The opening dynamics of the BMHV are modelled using fluidstructure interaction (FSI). The simulations show that differences occur in the leaflet movement of the three cases. In particular, with the asymmetric LV, one of the leaflets impacts the blocking mechanism at its open position with a 34% higher velocity than when using the velocity profile, and with an 88% higher velocity than in the symmetric LV case. Therefore, when simulating such an impact, the upstream boundary condition needs to be chosen carefully.

Assessing the Performance of Ultrafast Vector Flow Imaging in the Neonatal Heart via Multiphysics Modeling and <italic>In Vitro</italic> Experiments

“…The diastolic geometry created with ANSYS DesignModeler [ Fig. 2(a)] consisted of a truncated prolate spheroid [45], [46], with a long-axis to short-axis ratio (α) fixed to 2, and was topped with a circular outlet and ellipsoidal inlet representing, respectively, the aortic valve (Ø 6.5 mm) and the mitral valve (equivalent Ø 8.0 mm). The geometry was subsequently meshed with ANSYS ICEM CFD, resulting in a tetrahedral mesh of 378 480 cells.…”

“…A user-defined arbitrary Lagrangian-Eulerian mesh motion [51] defined on all interior nodes ensured that the mesh quality was preserved, while avoiding smoothing and remeshing. For further details, we refer to [45]. The Navier-Stokes equations were numerically solved with a finite volume method, and took 14 h and 50 min on a remote eight-core 64-b 3.4-GHz processor to acquire three full cardiac cycles.…”

A numerical study of ultrafast vector flow imaging in the neonatal heart

“…1, step 1) with its temporal volumetric change mathematically described ( Fig. 1, step 2) [8]. The resulting flow field is shown in diastole (t = 0.3 s) in Fig.1 (step 3).…”

Fluid–Structure Interaction and In Vitro Analysis of a Real Bileaflet Mitral Prosthetic Valve to Gain Insight Into Doppler-Silent Thrombosis

“…First, the approaches used to impose FSI, either through moving methods, as for the Arbitrary Lagrangian Eulerian (ALE) method [6][7][8][9][10], or through fixed grid methods consisting in evolutions of the Immersed Boundary (IB) method [11][12][13]. Second, the site of simulated BMV implantation, which is the aortic position in the vast majority of the published studies [7,8,[14][15][16][17], and is the mitral position only in few studies [18]. Third, the aim of the numerical analysis, which can range to the highly detailed quantification of shear stresses exerted on blood flowing through the valve as a mean to assess the risk of mechanically induced blood damage [16] to the assessment of intraventricular fluid dynamics associated to the presence of a BMV either in aortic [19] or mitral [18] position.…”