Numerical simulation of steady turbulent flow through trileaflet aortic heart valves--I. Computational scheme and methodology.

A numerical simulation model and technique are described to simulate steady turbulent blood flow through trileaflet tissue valves of varying degrees of stenosis. The aortic trileaflet tissue valve design was chosen as the subject of this study, since it is the only popular valve in current clinical use which is approximately axisymmetric. An axisymmetric geometry is computationally more convenient since it involves only two dimensional equations. The geometry and dimensions of the aorta were designed from angiographic studies and measurements made from cadavers. The valve dimensions were obtained from tissue leaflet photography studies conducted on tissue bioprostheses of varying degrees of stenosis. The non-rectangular nature of this valve necessitated the use of a body conforming grid. Thompson's method coupled with a Chimera grid system was chosen for this purpose. The Chimera grid was used to avoid a grid with highly skewed cells. Turbulence was simulated by using the kappa-epsilon model with the wall function method. This decision was made after comparing the kappa-epsilon model's performance with that of lower order models, and after considering the increased computer time requirements and decreased stability of more complex models, such as the Reynolds stress model. The results of the study which are very encouraging and compare favorably with in vitro experimental data, are described in Part II of the paper.