ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ignored the influence of the blood flow. The first fluid-structure interaction (FSI)
models of the aortic valve were primarily concerned with predicting the flow across
prosthetic mechanical valves with rigid leaflets, in both two-dimensional [3] and threedimensional
[4] models. Several FSI simulations of flexible valves have been also
conducted. Numerical instabilities, however, led to the use of unrealistically small
Reynolds numbers [5] or non-physiologic blood pressure [6] and the use of inadequate
mesh resolution [7]. Although coaptation during the diastolic phase affects valve
durability and function [8], most of the existing studies avoid simulating the coaptation
of flexible leaflets in a compliant root using FSI models [9]. The only study that did
investigate the coaptation using FSI models considered only the end-closing phase and
assumed isotropic and linear elastic leaflets [10]. The aim of the present study is to
present a full FSI model of healthy porcine aortic valve and root with physiologic blood
pressure and tissues properties.
3. METHODS
A three-dimensional (3D) geometry of a porcine aortic valve and root was reconstructed
using dimensions and geometric relationships similar to those suggested by Thubrikar
‎[8]. ‎Figure 1 illustrates a proposed aortic valve base geometry with dimensions that are
scaled with respect to the annulus diameter (dAA). The leaflets and the root were
assumed to have separate but tied geometries; the leaflets moved with the root at their
joint boundaries. Two straight rigid tubes were added upstream and downstream,
respectively, to move the flow boundary conditions away from the regions of interest.
Figure 1 A schematic view of the aortic valve healthy model showing the compliant region and
the added rigid tubes.
The structural solver employed an implicit nonlinear dynamic analysis with an implicit
direct displacement-based finite element method. The Collagen Fibre Network (CFN)
material model ‎[11] was employed for the leaflets tissues. The CFN model explicitly
recognizes the collagen fibres and elastin matrix using different layers of elements. The
hyperelastic behaviour of the two materials and the radii of the fibres in various regions
of the leaflet were calibrated to published experimental stress-strain curves from porcine
aortic valve [12]. The tissue of the aortic root was assumed to be isotropic and