HINGE FLOW IN A BILEAFLET MECHANICAL HEART VALVE (MHV)

The significance of flow structure within the hinge socket of (BMHV) has been reported in recent years. Adverse flow structures, e.g. stagnation, may lead to thromboses in those regions. Computational fluid dynamics (CFD) play a substantial role in exploring the microscopic hinge-flow. CFD investigation of the positive washing flows in the region of a protruded-design hinge is presented. The flow field is modeled as a quarter of the valve channel with one immersed hinge by applying the two symmetry planes of the BMHV. Unstructured grids are generated in the entire flow field with finer cells near the hinge region, including the micro clearance between the leaflet and hinge. The rounded edges of the hinge and leaflet are taken into account on the flow structures for the first time. The valve leaflets fully opens to 87°. A simplified sinusoidal velocity is initially applied at the inlet to mimic the time dependent flow through the valve. The CFD simulation of the pulsatile flow ran on SGI workstation (CRAY Origin 2000) using Fluent 5.05 codes. The CFD results show that complex 3D vortices are formed downstream of the hinges during the acceleration phase, however a partial washing flow is noted to develop near the end of the deceleration phase. This partial washing flow scours the hinge regions and hence avoids stagnation in the hinge regions.