FULLY-COUPLED FLUID-STRUCTURE SIMULATION OF TILTING-DISC VALVE IN PULSATILE FLOW

Abstract

In this study, a fully-coupled two-dimensional fluid-structure interaction software system for a pulsatile flow across a moving tilting-disc valve is developed. Unsteady transvalvular blood flow coupled with induced occluder motion has been examined in details. State-of-the-art computational fluid dynamics (CFD) methods are adopted in the present flow solver development. Incompressible finite-volume method is employed to solve the Reynolds-averaged Navier-Stokes equations in conservation form. To account for nonstationary occluder motion, the grid is generated and updated in each time-marching step using hybrid structure/unstructured grid method. A single-degree-of-freedom rotational occluder model is integrated simultaneously with the CFD time-stepping. The geometrical conservation law is strictly satisfied so as to avoid spurious results generated. For code validation, cases with known solutions are compared, and good agreement between the numerical and experimental results are achieved. It is found in the present study that strong shedding vortices occur in the valve closing phase. The pivot location is found to be sensitive for the attainable maximum valve opening angle and the dynamics of valve closure. Blood damage index is also introduced to assess the turbulence-induced stresses to the blood cells. Differences resulted from various upstream flow assumptions and coupled or prescribed occluder motion adopted in the analyses are examined using the abundant simulated results.