In recent years, flow investigations of recessed hinges of bileaflet mechanical heart valves have been carried out following reports of valve failure that may be due to flow mechanisms within the hinge socket contributing to thrombosis formation in this critical area. A structured grid model of a newly protruded hinge design was developed, and flow through this hinge design was studied using a computational fluid dynamics (CFD) code running on a supercomputer. Fine detail flow structure within the hinge socket was investigated under steady flow conditions. Results showed flow structure in the hinge region to be complex and three-dimensional. Shear stress within the hinge socket was low, and a pair of vortices was formed as a result of the protruded hinge stopper. A comparative model with recessed hinge that resembles the St. Jude Medical valve hinge design was modeled using an unstructured grid. Flow inside this hinge socket was dominated by reverse flow, and gradually developed into vortices that also had a high Reynolds number.