Investigation of enhanced peak lift performance and stall angle delay by attachment of Vortex Generators on blade surfaces of Vertical Axis Ocean Current Turbine

Abstract

Efforts to enhance the efficiency and self-starting capability of Vertical Axis Ocean Current Turbine (VAOCT) at low ocean current speeds have recently become a major area of study. As the VAOCT blades rotate, it experiences varying angles of attack (α) relative to the ocean's current direction. This study investigated the impact of Vortex Generators (VG) on the static NACA 0021 hydrofoil VAOCT blade by varying VG height (h) within an α range of 0°–180°. Computational Fluid Dynamics (CFD) simulations were employed for analyzing the case configurations, providing new insights modified VAOCT with VG on its blade surface. The performance of the NACA 0021 with VG showed improvement. The coefficient of lift (C_l) increased by up to 20.2% for the VG configuration with h 1% C at an α of 20°. For the VG with h 2.5% C, the C_l increased by up to 8%. The stall angle was delayed from 20° to 25° for the VG with h 1% C and from 20° to 30° for the VG with h 2.5% C. The flow over the blade with VG also qualitatively improved, evidenced by better pressure and velocity contours. These results indicate that VG can positively enhance VAOCT performance.