In this article, the performance of a radial flow turbine is determined in the framework of oscillating water column installations (OWC). The studied turbine redesigned and adapted from previous studies to this application, is analyzed in detail using CFD Fluent v16.2 and TurboGrid for mesh preprocessing. In particular, a 3D numerical model with high-quality hexahedral meshes (necessary to analyze the unsteady phenomena in the blade passages of the turbine) has been developed to obtain an enhanced prediction of the flow patterns. The results obtained through a full unsteady RANS resolution of the viscous and three-dimensional flow structures reveal the optimal performance of the radial turbine and confirm the expected improvements introduced during the redesign of the machine.