Numerical Analysis of the Performance of a Shrouded Vertical-Axis Water Turbine based on the NACA 0025 Blade Profile

This paper presents a numerical analysis of the performance of a five-bladed Darrieus vertical-axis water turbine, based on the NACA 0025 blade profile, for both bare nd shrouded configurations. A complete campaign of 2-D simulati ons, performed for several values of tip speed ratio and based on RANS unsteady calculations, has been performed to obtain the roto r t rque and power curves. Also the effect of a NACA-shaped central hy drofoil has been investigated, with the aim of evaluating the impact of a solid blockage on the performance of the shrouded rotor c onfiguration. The beneficial effect of the shroud on rotor overal l performances has clearly been evidenced, while the adoption of t he central hydrofoil has proved to be detrimental, being the r esulting flow slow down (due to the presence of the obstacle) much hig er with respect to the flow acceleration (due to the solid blockage eff ct). Keywords—CFD, vertical axis water turbine, shroud, NACA 0025